JP7162904B2 - Electroless deposition method for platinum group metals and alloys thereof, and plating bath used therefor - Google Patents

Description

The present invention provides a method for electroless deposition of platinum group metals and alloys thereof and plating baths used therein.

The platinum group metals (PGMs) consist of six elements - platinum, palladium, rhodium, iridium, ruthenium and osmium. The interest in plating platinum group metals and PGM alloys stems from their very wide range of uses. The PGM layer can provide corrosion resistance and can also be used as a decorative layer or a discoloration layer. Rhodium is typically plated as a wear-resistant decorative finish layer. PGMs are also known for their catalytic activity for many chemical reactions. PGMs are used in the manufacture of electronic devices and components, and as layers that provide protection against corrosion of base metals. For example, zinc plated palladium, ruthenium and their alloys are used as gold substitute contacts on connectors and printed wiring boards.

A platinum layer can also replace the gold-on-copper plating. In such materials, copper atoms tend to diffuse through the gold layer, causing discoloration of the surface and the formation of oxide and/or sulfide layers. For a gold-on-copper layer, typically a nickel layer must be used to provide a mechanical backing for the gold layer. However, in such modified gold-on-copper layers, a skin effect is frequently observed due to the high electrical resistance of nickel. Soldering gold-plated parts is also problematic because the gold dissolves in the solder. A 2-3 μm gold layer completely melts within 1 second during typical wave soldering conditions. Palladium and ruthenium are used as metal contacts on semiconductors such as GaAs and InP.

The plating of PGMs is a particularly suitable method for cost-effective use of PGMs, as PGMs (and their alloys) can be plated onto a variety of low-cost substrates using this approach. Electroless PGM plating is particularly suitable as this method allows the layer to be plated onto a non-conductive substrate. PGM plating on plastics can be applied in manufacturing flexible electronic components and flexible dye-sensitized solar cells [Dao V-D, et al.: Dry plasma reduction to synthesize carrier ed platinum nanoparticles for flexible dye-sensitized solar cells. J. Mater. Chem. A 2013, 1:4436-4443].

To date, a few PGM electroless deposition processes have been described in the literature [Electroless Plating: Fundamentals and Applications; Glenn O. Mallory and Juan B. Hajdu, Ed., William Andrew, 1990]. Moreover, most of them result in brittle, non-uniform deposits with a high flaking tendency. A literature survey suggests that most research on PGM plating has focused on the development of plating bath additives, with less emphasis on reducing agents. In virtually all methods of electroless deposition of PGM, one of the following reducing agents is used: hydrazine and its derivatives, borohydride or hydrogen hypophosphite. The redox potentials of these reducing agents are very low, so PGM plating involves hydrogen evolution, which leads to unfavorable conditions for PGM deposition, such as hydrogen embrittlement, flaking, and rough deposits.

It is generally known that platinum plating is a complicated and difficult process. Electrochemical methods of platinum deposition result in the formation of poorly sticky platinum black deposits. In the traditional method introduced by Keitel and Zschiegner, Pt deposition is performed from a "Pt" salt precursor. This is one of the few methods that result in relatively smooth Pt coatings [Keitel W and Zschiegner H: Electrodeposition of Platinum, Palladium and Rhodium. Trans. Electrochem. Soc. 1931, 59:273-275]. However, this plating requires high temperature operation and platinum deposition with very low cathodic current efficiency, typically less than 10%. Solutions containing sulfatodinitritoplatinum(II) have been prepared for commercial use under the name of DNS platinum plating solutions, and patent applications covering this type of plating bath have been filed in many countries [Hopkin et al. N and Wilson L: Bright platinum plating. Platinum Metals Review 1960, 4:56-58]. Currently used platinum plating solutions contain many additives to improve deposit quality. However, this approach is expensive and would have its own limitations and potential problems.

Although platinum metals are chemically inert, their surfaces are highly reactive, which is why these metals are widely used in heterogeneous catalysis. Platinum alloyed with palladium, rhodium and other PGMs is used in a variety of industrial scale processes. Nitric acid and agricultural fertilizer production, which require ammonia oxidation, create the highest demand for PGM catalysts. However, important applications for platinum catalysts can also be found in the production of polymeric materials, such as the production of silicone and vinyl acetate monomers. PGMs are used as catalysts in reforming and isomerization reactions in the petroleum industry. Rhodium catalysts are used in the production of basic alcohols and acetic acid, the latter also produced with ruthenium and iridium as catalysts. Dimensionally stable anodes consisting of titanium coated with either ruthenium or ruthenium-iridium alloys are used for chlorine generation on an industrial scale. Rough PGM deposits can be applied to fuel cells and the like. For all these applications, rough PGM deposits are beneficial because the higher surface area results in higher catalytic activity of the layer. However, platinum coatings obtained in plating baths without brighteners are usually brittle Feltham A and Spiro M: Platinized platinum electrodes. Chem. Reviews 1971, 71:177-193]. Often this process is accompanied by hydrogen evolution and platinum is reduced in solution. For more than half a century, Pt black deposition has been performed from solutions containing small amounts of lead acetate, which inhibits hydrogen evolution and improves Pt adhesion. However, in this procedure lead is incorporated into the layer and the resulting Pt deposit is contaminated with Pb, which is particularly undesirable for catalytic applications.

Currently, there is no technology for producing platinum layers on very large specific surface areas and with strong adhesion to substrates. Ultrathin layers or metal clusters can be obtained on oxides or silicon [M.B. Vukmirovic et al., ChemElectroChem 2016, 3: 1-7; A. Munoz-Noval, Electrochemistry Communications, 2016, 71: 9-12] . A few electrolytic and electroless plating techniques are available for platinum. A comparison of catalyst layers comprising platinum-rhenium bimetallic clusters on graphite obtained by evaporation and electroless plating methods is described in R. P. Galhenage, Phys. Chem. Chem. Phys., 2015, 17, 28354. there is Most of the other known plating methods result in a platinum layer only (ie, no means disclosed for plating platinum in combination with other PGMs). In all known methods plating can be carried out on certain solid supports such as copper or titanium. It is also necessary to control plating conditions, especially temperature and pH. Also, the plating baths typically used in this way are very difficult to obtain as they contain many additives and reducing agents such as hydrazine and its derivatives or hypophosphorous acid. Finally, any smooth layer can only be obtained by electroplating, but with very low current efficiencies.

On the other hand, chemical reduction of platinum precursors is widely used for the production of platinum nanoparticles. Very popular reducing agents for platinum nanoparticles preparation are aliphatic alcohols and aldehydes. One of the prerequisites for nanoparticle preparation is a fast reduction step, usually carried out at relatively high temperature (typically the temperature of the reduction step is higher than 70°C). At lower temperatures stronger reducing agents such as hydrazine have to be used [WO2013186740].

Oxidation of alcohols has been extensively investigated because of their possible use in fuel cells. The most extensive studies were performed on methanol and to a lesser extent on ethanol. Oxidation of other alcohols has been occasionally reported. Polyhydroxy compounds, namely sugars and sugar derivatives, such as glucose, ascorbic acid, have previously been used to plate silver and gold [Kato M et al.: Electroless Gold Plating Bath Using Ascorbic Acid as Reducing Agent- Recent Improvements. In Proceedings of AESF Technical Conf SUR/FIN'95:1995:805-813]. Aliphatic and aromatic monoalcohols have never been used before as reducing agents in electroless plating.

Due to the great demand for platinum and other PGM coated articles, there is a great need to develop a method for electroless deposition of platinum and other PGMs that will result in the formation of well adherent metal layers. . Moreover, there is a need for a PGM electroless plating method in which the properties of the metal layer formed can be easily controlled simply by varying the process conditions. Also, the plating baths used in such PGM electroless plating methods do not contain brighteners (such as saccharin and polyethylene glycol) and other additives and reducing agents (such as hydrazine, lead or hypophosphite). It would be advantageous if

The inventors of the present invention have developed a method for electroless deposition of platinum and other PGMs, and their alloys, using aromatic and aliphatic alcohols as catalysts. As used herein, PGM layers include layers of single metals (such as platinum, palladium, rhodium, iridium, ruthenium and osmium) and metal alloy layers containing platinum group metals (such as platinum-rhodium, platinum-iridium, platinum-ruthenium, etc.), as well as metal alloy layers containing platinum group metals and other metals such as gold, nickel and copper (eg platinum-gold, platinum-copper, platinum-nickel, platinum-rhodium-gold, rhodium - Nickel, etc.). In a most preferred embodiment of the invention, an alloy layer is deposited on the substrate, said alloy containing one or more metals from the group comprising platinum, palladium, rhodium, iridium, ruthenium, osmium, gold, nickel and copper. include.

Both primary and secondary alcohols are used in the method of the invention and deposition is carried out on a wide variety of substrates including metals and alloys, polymeric materials, graphite and silicon. The PGM plating process of the present invention is performed at a temperature between the freezing and boiling points of the plating bath. Controlling both the layer thickness and the surface morphology of the deposited layer in a simple manner by adjusting the experimental conditions, in particular the reducing agent, temperature, pH and the concentration of both the reducing agent and the platinum group metal precursor. can be done.

In particular, according to the present invention, a method for electroless deposition of platinum group metals and alloys thereof from a plating bath onto a substrate comprises a step of reducing one or more platinum group metal precursors with a reducing agent, said reduction The agent is a primary or secondary monohydroxy alcohol or a mixture of primary or secondary monohydroxy alcohols. As used herein, the term "monohydroxy alcohol" refers to aliphatic and aromatic alcohols containing a single hydroxyl group. The term "primary monohydroxy alcohol" means an alcohol in which the hydroxyl group is attached to a carbon atom having only the primary carbon atom-1 adjacent carbon atom (i.e., an alcohol having the group "-CH ₂ OH" ) should be understood as The term "secondary monohydroxy alcohol" means an alcohol in which the hydroxyl group is attached to a carbon atom having a secondary carbon atom-2 adjacent carbon atoms (i.e., the group "-CHROH" below, where R is a carbon Alcohols with containing groups (aliphatic or aromatic) are to be understood. As used herein, the term "mixture of primary or secondary monohydroxy alcohols" includes mixtures of different primary monohydroxy alcohols, mixtures of different secondary monohydroxy alcohols, and primary monohydroxy alcohols and secondary monohydroxy alcohols. The term "electroless deposition" is well known to those skilled in the art and refers to the process of metal deposition onto a substrate by reduction of metal ions from solution without the use of an external electron source.

式中、R₁およびR₂は同じでも異なっていてもよく、それらの各々は独立に水素原子、直鎖または分枝のC_1-7-アルキル基、C_3-8-アリール基、C_4-8-アラルキル基およびC_4-8-アルカリール基を含む群より選択される。「アルキル」は、非環式、分枝または非分枝、飽和の一価のヒドロカルビル基を意味する。アルキルは、メチル、エチル、プロピル、ブチル、ペンチル、ヘキシル、ヘプチルおよびオクチル、ならびに分枝の飽和の一価のヒドロカルビル基で例示されるが、これらに限定されない。「アリール」は、環式、完全に不飽和なヒドロカルビル基を意味する。アリールは、シクロペンタジエニルおよびアリールで例示されるが、これらに限定されない。「アラルキル」は、ペンダントアルキル基を有するアリール基を意味する。「アルカリール」は、ペンダントおよび／または末端アリール基を有するアルキル基を意味する。 Preferably, said monohydroxy alcohol has the general formula:

wherein R ₁ and R ₂ may be the same or different and each of them independently represents a hydrogen atom, a linear or branched C _1-7 -alkyl group, a C _3-8 -aryl group, a C ₄ is selected from the group comprising _-8 -aralkyl and _C4-8 -alkaryl groups; "Alkyl" means an acyclic, branched or unbranched, saturated monovalent hydrocarbyl group. Alkyl is exemplified by, but not limited to, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl and octyl, and branched saturated monovalent hydrocarbyl groups. "Aryl" means a cyclic, fully unsaturated hydrocarbyl group. Aryl is exemplified by, but not limited to, cyclopentadienyl and aryl. "Aralkyl" means an aryl group having a pendant alkyl group. "Alkaryl" means an alkyl group having pendant and/or terminal aryl groups.

Preferably, R ₁ and R ₂ in the above formula are independently _-H , _-CH3 , _-C2H5 , _-C3H7 , _{-CH (CH3)2 , -C4H9 ,} - _CH2CH ( _CH3 ) ₂ , -CH( _CH3 ) _C2H5 , -C _{( CH3} ) _{3 , -C5H11 ,} -CH _{( CH3} ) _C3H7 , -CH2CH( _CH3 ) _{C2H5, -C2H4CH(CH3)2 , -C ( CH3 ) 2C2H5 ,} -CH _{( CH3} )CH _{( CH3} ) ₂ , _-CH2C ( _CH3 ) ₃ , _{-CH ( C2H5} ) ₂ , _-C6H13 , _-C7H15 , and _{-CH ( C2H5} ) _{( C4H9} ). More preferably, said monohydroxy alcohol is methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methylpropan-1-ol, 1-pentanol, 3-methylbutane-1- ol, 2-methylbutan-1-ol, 2,2-dimethylpropan-1-ol, 3-pentanol, 2-pentanol, 3-methyl-2-butanol, 1-hexanol, 2-hexanol, 2-methyl -1-pentanol, 3-methyl-1-pentanol, 4-methyl-1-pentanol, 3-methyl-2-pentanol, 4-methyl-2-pentanol, 2-methyl-3-pentanol , 2,2-dimethylbutan-1-ol, 2,3-dimethylbutan-1-ol, 3,3-dimethylbutan-1-ol, 3,3-dimethylbutan-2-ol, 2-ethylbutan-1 -ol, 1-heptanol, 2-heptanol, 3-heptanol, 4-heptanol, 1-octanol, 2-octanol and 2-ethylhexan-1-ol. Most preferably, said monohydroxy alcohol is methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methylpropan-1-ol, 1-pentanol, 3-methylbutane-1- ol, 2-methylbutan-1-ol, 2,2-dimethylpropan-1-ol, 3-pentanol, 2-pentanol, 3-methyl-2-butanol, 1-hexanol, 1-heptanol and 1-octanol selected from the group comprising

Some of the monohydroxy alcohols mentioned above exist in specific stereoisomeric forms. For example, 2-butanol can be obtained as either of the two stereoisomers -(R)-(-)-2-butanol and (S)-(+)-2-butanol. The present invention contemplates such stereoisomers as separate isomers, as well as racemic and other mixtures thereof.

The concentration of said monohydroxy alcohol in said plating bath used in the method of the present invention is in the range of 0.02 to 12M, preferably in the range of 0.1 to 5M. The solubility of monohydroxy alcohols, which are sparingly soluble in water, can be increased by conversion of 2-methylpropan-2-ol. Therefore, in one aspect of the invention, the plating bath used in the method of the invention further comprises 2-methylpropan-2-ol.

According to the invention, said platinum group metal precursors used in the process of the invention _are preferably _H2PtCl6 , _H6Cl2N2Pt , _PtCl2 , _PtBr2 , _K2 [ _{PtCl4 ]} , _{Na 2} [ _PtCl4 ], Li2[ _PtCl4 ], H2Pt(OH) ₆ , Pt( _NO3 ) ₂ , [Pt( _NH3 ) ₄ ] _Cl2 , [Pt _{( NH3} ) ₄ ] _{( HCO3} ) ₂ , [Pt( _NH3 ) ₄ ](OAc) ₂ , ( _NH3 ) _{4Pt ( NO3} ) ₂ , ₍ NH4) _2PtBr6 , _K2PtCl6 , _PtSO4 , Pt _{( HSO4} ) ₂ , Pt _{( ClO4} ) ₂ , _K2PtI6 , K2[Pt _{(CN)4 ]} , _cis- [ _{Pt ( NH3} ) _2Cl2 ], _H2PdCl6 , _H6Cl2N2Pd , _{PdCl 2} , _PdBr2 , K2[ _PdCl4 ], Na2[ _PdCl4 ], Li2[ _PdCl4 ], _H2Pd (OH) ₆ , Pd _{( NO3} ) _{2 ,} [Pd _{( NH3} ) ₄ ]Cl ₂ , [Pd( _NH3 ) ₄ ]( _HCO3 ) ₂ , [Pd( _NH3 ) ₄ ](OAc) ₂ , ( _NH4 ) _2PdBr6 , _{( NH3} ) _2PdCl6 , _PdSO4 , Pd ₍ HSO4) ₂ , Pd( _ClO4 ) ₂ , Pd(OAc) ₂ , _RuCl2 ((CH3) _2SO ) ₄ , _RuCl3 , [Ru( _NH3 ) _{5 ( N2} )] _Cl2 , Ru(NO ₃ ) ₃ , _RuBr3 , _RuF3 , Ru( _ClO4 ) ₃ , _K2RuCl6 , _OsI , _OsI2 , _OsBr3 , _OsCl4 , _OsF5 , _OsF6 , _OsOF5 , _OsF7 , _IrF6 , _IrCl3 , _IrF4 , _IrF5 , Ir( _ClO4 ) ₃ , K3[ _IrCl6 ], K2[ _IrCl6 ], _Na3 [ _IrCl6 ], _Na2 [ _IrCl6 ], _Li3 [ _{IrCl6 ] ,} Li ₂ [ _IrCl6 ], [Ir( _NH3 ) _4Cl2 ]Cl, _RhF3 , _RhF4 , _RhCl3 , [Rh _{( NH3} ) _5Cl ] _Cl2 , RhCl[P(C _6H5 ) ₃ ] ₃ , K[Rh(CO) _2Cl2 ], Na[Rh ₍ CO) _2Cl2 ]Li[Rh ₍ CO) _2Cl2 ], _Rh2 ( _SO4 ) _{3 ,} Rh ₍ HSO4) ₃ , Rh( _ClO4 ) _{3 ,} hydrates thereof and mixtures of salts and/or hydrates thereof. The term "platinum group metal precursor" should be understood as any salt or complex of a platinum group metal capable of being deposited in a plating bath, which can be reduced to the metallic form deposited on the substrate.

In a preferred embodiment, the platinum group metal precursor concentration in the plating bath used in the method of the present invention is in the range of 1 mM to 1 M, more preferably in the range of 5 mM to 100 mM, most preferably 10 mM to 50 mM. mM range.

In a preferred embodiment, the reduction step in the method of the invention is performed at a temperature between the freezing point and the boiling point of the plating bath. Preferably, the temperature of said reduction step in the process of the invention is -10 to 80°C, more preferably 0 to 40°C, most preferably 10 to 25°C.

In preferred embodiments, the pH of the plating bath used in the method of the present invention is below 7, preferably between 3 and 5, most preferably about 4. The best deposition is obtained when the pH of the plating bath is about 4.

As used herein, substrate or support refers to any material onto which PGMs and their alloys are deposited. Examples of suitable substrates/monoliths are metals such as platinum, palladium, nickel and gold, metal alloys such as steel, iron-chromium-aluminum alloys (Kanthal®), polymeric materials such as Nafion® , polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), carbon (eg graphite) and silicon. More preferably, the substrates used in the method of the present invention are platinum, palladium, nickel, gold, steel, iron-chromium-aluminum alloys, Nafion®, polyethylene, polypropylene, polyethylene terephthalate, graphite and silicon. selected from the group comprising

In a preferred embodiment of the invention, the surface of the substrate on which the PGM is deposited is seeded prior to the reduction step. According to the invention, any standard process of surface seeding can be used. One preferred seeding method is the zincation method in which zinc is deposited on the substrate surface from a solution containing chlorite ions in the presence of metallic zinc. Alternatively, seeding may be performed with tin(II) ions.

After the PGM is deposited on the substrate, it can be subjected to high temperature treatment. This heat treatment can be used to add rough surface deposits to deposits with smooth surfaces. This process can only be performed for PGM layers deposited on substrates that can withstand high temperatures (eg metals, alloys and silicon). Therefore, in preferred embodiments, the method of the present invention further includes a step of high temperature treatment after the plating process is completed. Said high temperature treatment is preferably carried out at a temperature of 700-1000°C. More preferably, the substrate with PGM precipitates is flame annealed. Most preferably the high temperature treatment is carried out in a hydrogen flame.

To avoid pH changes during the PGM deposition process, in preferred embodiments the plating bath further contains a pH buffer. Preferably, a Britton-Robins buffer is used in the plating bath. Other buffering agents can also be used. Examples of such buffers include phosphate, acetate, citrate, and borate buffers.

Although the addition of brighteners is not required by the method of the present invention, their addition is also contemplated herein. Therefore, in a preferred embodiment, the plating bath used in the method of the present invention further comprises brighteners such as saccharin, polyethylene glycol, paratoluenesulfonamide, benzenesulfonic acid, sodium allylsulfonate, pyridine propylsulfonate. Moreover, in addition to the primary or secondary monohydroxy alcohol or mixture of primary or secondary monohydroxy alcohols, another reducing agent can be used in the process of the present invention. Therefore, in another embodiment of the invention, the plating bath used in the method of the invention further comprises hydrazine and its derivatives, borohydride or hydrogen hypophosphite as additional reducing agents.

In another aspect, the present invention provides a plating bath for the electroless deposition of platinum group metals and alloys thereof, said plating bath comprising a primary or secondary monohydroxy alcohol or a secondary monohydroxy alcohol as a reducing agent. An aqueous solution containing a mixture of primary or secondary monohydroxy alcohols and one or more platinum group metal precursors. The plating bath of the invention, as well as its components, are described above with reference to the method of the invention.

Finally, the invention provides the use of a plating bath as defined above in the electroless deposition of platinum group metals.

Based on numerous experiments performed by the inventors, no simple trends were observed in the deposition rates of platinum and other PGMs, and in the molecular weights of the homologous series of alcohols. At ambient temperature, the electroless deposition rate decreased with the following order of reducing agents in a series of short-chain water-miscible alcohols: ethanol, methanol, 2-propanol, 1-propanol, 2-butanol. The higher the PGM deposition rate (either in the presence of ethanol or at elevated temperatures), the higher the specific surface area of the deposit, which is typical of rough deposits. For catalytic applications where high specific surface area is advantageous, ethanol should be used as reducing agent. Poorly water-soluble alcohols, such as 1-butanol and 1-pentanol, used as reducing agents also lead to the formation of very rough deposits. The brightest deposits were obtained for 1-propanol and 2-propanol at ambient temperature.

The observed trends for the various monohydroxy alcohols used in the method of the invention can be summarized as follows:
• Methanol—results in the formation of a rough layer.
• Ethanol - results in the formation of a rough, grey-black deposit; however, precipitation at a lower temperature (about 4°C) results in the formation of a smooth deposit.
• 2-propanol - results in the formation of a smooth deposit (smooth and shiny).
In general, the low temperature of the process of the present invention results in smooth deposits. Moreover, deposits are more likely to form on metal substrates when the process of the present invention is carried out in the presence of secondary alcohols as reducing agents. In the case of primary alcohols, deposits are more likely to form on polymeric materials. Depending on the properties of the substrate in this manner, selective deposition can be achieved by choosing a suitable monohydroxy alcohol as reducing agent.

The inventors have also recognized the following mechanisms for the method of the invention:
- temperature can be used to control the process;
- The speed of the process is decisive for the properties of the deposit (slower speed gives a smoother deposit layer)
- In the process of the present invention, carbon monoxide is formed as one of the intermediates in the alcohol oxidation reaction, which can act as a brightener;
• Good adhesion of the precipitate may be related to the seeding process rather than the rate of reaction.

The method of the invention has many advantages. First of all, a good adhesion layer of PGMs and their alloys is obtained. The PGM layers deposited by the method of the invention are very stable and durable (e.g. they remained unchanged over 12 months after deposition; they remained stable in electrochemical experiments; they remains stable under mechanical stress). These layers can be dense and uniform or have a very rough surface, depending on the deposition conditions. PGM layers include metals (e.g. platinum, palladium, nickel and gold), metal alloys (steel, Kanthal), polymeric materials (e.g. Nafion, PE, PP, PET), carbon (e.g. graphite) and on various substrates, including silicon. The process can be carried out over a wide temperature range (-10 to 80°C) and temperature control is not critical depending on the reducing agent used. Therefore, the plating process can be performed at room temperature. Moreover, the plating bath of the present invention has a very simple composition, can be easily prepared, and is very stable.

Due to its universal nature, the method of the present invention is useful in various fields of technology, especially due to the fact that PGM can be plated on various supports. for example:
- PGM-plated Nafion® and graphite can be used as fuel cell electrodes;
- PGM-plated plastics (polymer materials) can be used in flexible electronics (flex circuits);
- PGM-plated metals (steel, Kanthal) can be used as catalysts;
- PGM plated silicon can be used as electrical contacts;
• PGM plating can also be used for the production of non-corrosive electrical contacts and in the jewelry industry.

The subject matter of the invention is illustrated in the drawing.

1 shows a photograph of a Pt-plated platinum foil obtained as described in Example 1. FIG. FIG. 2 shows photographs of Pt-plated Kanthal® (a), Nafion® (b), PP (c) and PET (d) obtained as described in Example 2. show. Figure 3 shows (a) a photograph of a platinum-coated gold plate obtained as described in Example 3 and (b) an SEM micrograph of the platinum layer thus obtained. 4 shows (a) a photograph of a platinum-coated graphite disc and (b) a photograph of a platinum-coated steel plate obtained as described in Example 4. FIG. 5 shows a photograph of platinum deposited on a platinum-coated copper rod obtained as described in Example 5. FIG. FIG. 6 shows XP spectra in the Pt 4f/Ir 4f region for the alloy precipitates prepared as described in Example 7. Figure 7 shows SEM micrographs of the alloy layers obtained on gold substrates, obtained as described in Example 8: (a) alloy Rh-Pt(MeOH); (b) Ru(MeOH) ( (magnification 2,50K x); (c) Ru(MeOH) (magnification 100,00K x); (d) alloy Pt-Ir(MeOH) (magnification 50.00 K x) (e) alloy Pt-Ir(MeOH) (magnification 1.00 K x); (f) alloy Rh-Pt(EtOH); (g) alloy Ru-Pt(EtOH); (h) alloy Ir-Pt(EtOH); (i) alloy Rh-Pt (isopropanol) (magnification (1 K x); (j) alloy Ir-Pt (isopropanol) (magnification 1.00 K x); (k) Ru (isopropanol) (magnification 5.00 K x); (l) Ru (isopropanol) (magnification 50.00 K x); (n) alloy Ir-Pt (isopropanol) (magnification 1.00 Kx); (o) Ir-Pt (isopropanol) (magnification 50.00 Kx). Figure 8 shows micrographs of alloy layers obtained on gold substrates in Example 9: (a) alloy Ru-Pt1:2(EtOH) (magnification 2.50 Kx); (b) alloy Ru-Pt1: 6 (EtOH) (magnification 25.00 K x); (c) alloy Pt-Ir(BuOH) (magnification 1.00 K x); (d) alloy Pt-Ir(BuOH) (magnification 50.00 K x). 9 shows photographs of platinum deposits on PET and PP substrates, obtained as described in Example 10. FIG. Figure 10-1 shows data for platinum deposits obtained using various reducing agents, as described in Example 11: (a) electroless deposition according to the invention using various reducing agents; cyclic voltammograms recorded for a platinum layer plated on Pt by Cyclic voltammograms were recorded in 0.5 M sulfuric acid at a scan rate of v = 1 mVs ^-1 . (b) Scanning electron micrograph of a platinum layer deposited on platinum from a methanol-containing bath. FIG. 10-2 shows data for platinum deposits obtained using various reducing agents, as described in Example 11: (c) Platinum layer deposited on platinum from bath containing 2-propanol. (d) Scanning electron micrograph of a platinum layer deposited on platinum from a bath containing 2-butanol. FIG. 11 shows Pt-Ir alloy precipitates obtained with different reducing agents, as described in Example 13, recorded in 0.5 mol dm ⁻³ H ₂ SO ₄ and 0.5 mol dm ⁻³ ethanol. voltammogram is shown.

Example 1. Platinum deposition on platinum foil
A 0.7 x 0.7 x 0.01 cm diameter platinum foil was hydrogen flame annealed and quenched in deionized water. 0.01 M [ _PtCl4 ] ^2- + 0.04 _{MH3BO3 ,} 0.04 _MH3PO4 and 0.04 M _{CH3COOH ,} pH = 4.06 with sodium hydroxide. was immersed in a solution containing Britton-Robins buffer adjusted to The plating bath was held at room temperature for 10 hours. A 2 μm thick metallic silver shine coating was thus obtained with a yield of 98%. Deposition layer thickness and deposition yield were determined based on the weight change of the substrate. Figure 1 shows a photograph of a Pt-plated platinum foil.

Example 2. Platinum deposition on _Kanthal® , PET, PP, ^Nafion® and silicon substrates. It was immersed in a solution containing Britton-Robins buffer containing ₃ BO ₃ , 0.04 MH ₃ PO ₄ and 0.04 M CH ₃ COOH, adjusted to pH=4.06 with sodium hydroxide. The plating bath was held at room temperature for 12 hours. A metallic silver shine coating was obtained on the Kanthal® surface. FIG. 2(a) shows a photograph of a Pt-plated Kanthal® plate.

The above method was also used for platinum deposition on polypropylene (PP), polyethylene terephthalate (PET), Nafion® and silicon. Metallic silver shine coatings were obtained on silicon, PP and PET substrates, while gray-black coatings were obtained on Nafion®. Platinum-coated Nafion®, PP and PET are shown in Figures 2b-d, respectively.

In a corresponding manner, a platinum metallic silver shine layer was obtained on a PP substrate from a solution with pH 4 and containing 7.5 mM [PtCl ₄ ] ^2- using 2.5 M 1-propanol.

Example 3. Platinum deposition on gold substrate
A 0.7 × 0.7 × 0.05 cm diameter gold plate was seeded using the zincation method (in the presence of metallic zinc in 1 M Na ₂ [Zn(OH) ₄ ], the mass of deposited Zn was 50 μg was equal to ). 0.01 M [ _PtCl4 ] ^2- + 0.04 _{MH3BO3 ,} 0.04 _MH3PO4 and 0.04 M _{CH3COOH ,} pH = 4.06 with sodium hydroxide. was immersed in a solution containing Britton-Robins buffer adjusted to The plating bath was held at room temperature for 12 hours. A 2.4 μm thick metallic silver shine coating was thus obtained with a yield of 95%. Figure 3a shows a photograph of a platinum-coated gold plate. A SEM micrograph of the precipitate is shown in Figure 3b.

Example 4. Platinum Depositions on Nickel, Steel and Graphite Substrates Platinum deposits on nickel, steel and graphite substrates were obtained as described in Example 3. A metallic silver shine platinum coating was obtained on all substrates. FIG. 4 shows a photograph of a platinum-coated graphite disc (a) and a platinum-coated steel plate (b).

Example 5. Platinum Deposition on Silver, Palladium, PET, PP and Nafion® Substrates Platinum deposition on silver, palladium, PET, PP and Nafion® substrates was performed as described in Example 3. , except that tin(II) chloride (SnCl ₂ ) was used instead of Na ₂ [Zn(OH) ₄ ] for seeding the substrate surface. A metallic silver shine platinum coating was obtained on all substrates. FIG. 5 shows a photograph of a platinum deposit on a platinum coated copper rod with 200 nm of palladium.

Example 6. Preparation of roughened platinum layers for catalytic applications
A 0.7 x 0.7 x 0.01 cm diameter platinum foil was hydrogen flame annealed and quenched in deionized water. The substrate was then adjusted to _pH = _4.06 with _{sodium hydroxide} containing ^2.85 _{M ethanol} ; immersed in a solution containing Britton-Robins buffer. The plating bath was held at room temperature for 1 hour. A 0.4 μm thick sticky grey-black coating was thus obtained with a specific roughness factor R _f = A _specific / A _geometric = 130. Here, A _specific and A _geometric are the specific surface area and geometric surface area of the precipitate, respectively. Taking into account the precipitate mass m=1.63 mg, this corresponds to a mass specific surface area of 16.3 m ² /g.

This type of platinum deposit is particularly suitable for use in catalytic applications.

Example 7. Preparation of platinum-iridium alloys on gold substrates
A 0.2 × 0.05 cm system of gold discs was seeded using the zincation method (in the presence of metallic zinc in 1 M Na ₂ [Zn(OH) ₄ ], the mass of deposited Zn was equal to 20 μg). rice field). The substrate was then adjusted to _{pH =} ^4.06 with _{sodium hydroxide} containing ₄ M _methanol ; immersed in a solution containing Britton-Robins buffer. The plating bath was kept at room temperature for 24 hours. A 1 μm thick metallic silver shine coating was thus obtained with a yield of 95%.

The chemical composition and chemical properties of the deposits were investigated by X-ray photoelectron spectroscopy. Using this method, the metallic properties of iridium were confirmed. The X-ray spectrum of the Pt 4f/Ir 4f region showed two doublets. The doublets with components at 60.71 eV and 63.69 eV can be assigned to metallic Ir (Ir 4f _7/2 and Ir 4f _5/2 signals, respectively), whereas the signals at 71.34 eV and 74.67 eV are Pt (Pt 4f _7/2 and Pt 4f _5/2 signals, respectively) can be assigned. Literature positions for metallic Ir and Pt: 60.81 eV and 63.76 eV for signals of Ir 4f _7/2 and Ir 4f _5/2 respectively and 71.09 eV and 71.09 eV for signals of Pt 4f _7/2 and Pt 4f _5/2 respectively 74.42 eV (NIST X-ray Photoelectron Spectroscopy Database, Version 4.1 [National Institute of Standards and Technology, Gaithersburg, 2012); http://srdata.nist.gov/xps/.]) was marked with a vertical line. Small differences between measured and literature peak positions are most likely due to alloy formation [Adam Lewera et al.: Core-level Binding Energy Shifts in Pt-Ru nanoparticles: A puzzle resolved Chem. Phys. Lett. 2007, 44: 39-43). The small doublets at about 76.69 eV and 80.02 eV are probably related to the presence of small amounts of unreduced Pt, most likely in the form of Pt(IV) compounds. The ratio of Pt to Ir determined from XPS data is equal to 75:25 atomic percent (Pt:Ir). FIG. 6 shows XP spectra in the Pt 4f/Ir 4f region. Two signal doublets can be clearly seen, one for Pt and the second for Ir. The reference positions of the Pt and Ir signals for the fully reduced metals are marked with vertical lines.

Example 8. Preparation of platinum-rhodium, -ruthenium, -palladium and -iridium alloys on gold substrates. were prepared: platinum-rhodium, platinum-ruthenium, platinum-palladium and platinum-iridium. The plating process was carried out in a manner corresponding to that described in Example 7, but with ₃ mM _K2PtCl6 as the platinum precursor and, in successive examples, with 5 M MeOH, 3,5 M EtOH as reducing agents. and 2,6 M isopropanol with 6 mM Rh ²⁺ , 6 mM Ru ²⁺ , 7 mM Pd ²⁺ , and 6 mM Ir(IV) as the second PGM in the alloy. The table below summarizes the conditions used for the alloy plating of the substrates, as well as the properties of the resulting layers. Alloy formation and their compositions were determined by EDS (data are included in the table).

Example 9. Preparation of platinum-rhodium, -ruthenium, -palladium and -iridium alloys on Kanthal substrates Layers of platinum-ruthenium and platinum-iridium alloys were prepared using the procedures described in Examples 8 and 9. The difference was that a Kanthal substrate was used as the solid support for the layers to be formed, and various alcohols--ethanol and sec-butanol--as reducing agents. The table below summarizes the conditions used for the alloy plating of the substrates, as well as the properties of the resulting layers. Alloy formation and their compositions were determined by EDS (data are included in the table).

Example 10. Platinum Layers on PET and PP Substrates Obtained Using Ethanol As described in Example 2, platinum layers were obtained on PET and PP substrates. However, instead of 2-propanol, ethanol was used as reducing agent. A metallic silver shine coating was obtained. FIG. 9 shows photographs of platinum deposits on PET and PP substrates.

Example 11. Deposition of platinum layers on platinum substrates using different reducing agents The effect of different reducing agents on the properties of the deposit was investigated. Therefore, various reducing agents were used to obtain platinum layers on platinum substrates. Prior to deposition, platinum electrodes were flame annealed and quenched in deionized water. Platinum was deposited from the plating bath as in Example 1, but with different reducing agents at a concentration of 2M. Cyclic voltammograms were recorded in 0.5 H ₂ SO ₄ after 12 h precipitation.

The roughest deposit was obtained with the methanol-containing bath, which corresponds to the highest current density in the cyclic voltammogram (Fig. 10a).

Scanning electron micrographs of the surfaces of selected deposits are shown in Figures 10b, c and d. The material has a typical "cauliflower-like" surface consisting of micrometer-sized spherical structures. A regular high magnification of the resulting layer shows the nanocrystalline/amorphous structuring of the material. At lower magnifications, a tendency towards stress fracture of the material was seen (not shown here). Also, some tendency for dendrite-like growth of the coating is observed. Cross-sectional fracture indicates some degree of internal fibrous structuring of the coating in the growth direction.

The samples obtained from the 2-propanol containing bath are much smoother compared to the other samples. Higher magnification pictures show the structured material at the nanometer scale. There is some tendency to fragmentation, but they are much less numerous. Also, the shape suggests a higher plasticity of this coating. Presumably, some of the fractures seen are related to stress in the base. Cross-sectioning of the samples shows no tendency for internal structuring of the coating.

The morphology of the sample obtained from 2-butanol is shown in Figure 10c. The surface of the precipitate is fairly smooth. Some nodular structures on the micrometer scale are seen, much like the samples obtained with methanol, but in much lower numbers. Cross-sectional fracture indicates no internal structuring of the material. All 3 samples closely resemble the morphology of the base carrier. Moreover, even when crushed, the precipitate remains sticky to the substrate material (Fig. 10b). Coating defects can be eliminated by the use of additives in the metallization process or by slight changes in the physical parameters (ie temperature) of the process.

Example 12. Mechanical Properties of Platinum Layers on PET, PP and Nafion® Substrates The platinum-coated PET, PP and Nafion® substrates obtained in Examples 2 and 5 were subjected to mechanical stress tests. provided. All platinum coated substrates were folded, stretched and twisted by hand. After testing, all substrates were examined for the integrity of the platinum coating. No deposit changes, such as cracks or delamination, were observed. The fact that the platinum layer remained intact during the mechanical stress test indicates the outstanding integrity and very good adhesion of the deposited platinum layer to the polymeric material substrate.

Example 13. Electrochemical Properties of PGM Deposited Layers on Gold, Kanthal®, and Platinum Substrates The electrochemical properties of PGM deposited layers on gold, Kanthal®, and platinum substrates were investigated. In Experiment 1, the deposit-substrate assembly obtained in Examples 1-11 was used to oxidize ethanol.

式中、R ₁ およびR ₂ は同じでも異なっていてもよく、それらの各々は独立に水素原子、直鎖または分枝のC _1-7 -アルキル基、C _3-8 -アリール基、C _4-8 -アラルキル基およびC _4-8 -アルカリール基を含む群より選択される。
［３］ R ₁ およびR ₂ は独立に、-H、-CH ₃ 、-C ₂ H ₅ 、-C ₃ H ₇ 、-CH(CH ₃ ) ₂ 、-C ₄ H ₉ 、-CH ₂ CH(CH ₃ ) ₂ 、-CH(CH ₃ )C ₂ H ₅ 、-C(CH ₃ ) ₃ 、-C ₅ H ₁₁ 、-CH(CH ₃ )C ₃ H ₇ 、-CH ₂ CH(CH ₃ )C ₂ H ₅ 、-C ₂ H ₄ CH(CH ₃ ) ₂ 、-C(CH ₃ ) ₂ C ₂ H ₅ 、-CH(CH ₃ )CH(CH ₃ ) ₂ 、-CH ₂ C(CH ₃ ) ₃ 、-CH(C ₂ H ₅ ) ₂ 、-C ₆ H ₁₃ 、-C ₇ H ₁₅ 、および-CH(C ₂ H ₅ )(C ₄ H ₉ )を含む群より選択される、［1］または［2］の方法。
［４］ 前記モノヒドロキシアルコールは、メタノール、エタノール、1-プロパノール、2-プロパノール、1-ブタノール、2-ブタノール、2-メチルプロパン-1-オール、1-ペンタノール、3-メチルブタン-1-オール、2-メチルブタン-1-オール、2,2-ジメチルプロパン-1-オール、3-ペンタノール、2-ペンタノール、3-メチル-2-ブタノール、1-ヘキサノール、2-ヘキサノール、2-メチル-1-ペンタノール、3-メチル-1-ペンタノール、4-メチル-1-ペンタノール、3-メチル-2-ペンタノール、4-メチル-2-ペンタノール、2-メチル-3-ペンタノール、2,2-ジメチルブタン-1-オール、2,3-ジメチルブタン-1-オール、3,3-ジメチルブタン-1-オール、3,3-ジメチルブタン-2-オール、2-エチルブタン-1-オール、1-ヘプタノール、2-ヘプタノール、3-ヘプタノール、4-ヘプタノール、1-オクタノール、2-オクタノールおよび2-エチルヘキサン-1-オールを含む群より選択される、［1］～［3］のいずれか一つの方法。
［５］ 前記モノヒドロキシアルコールは、メタノール、エタノール、1-プロパノール、2-プロパノール、1-ブタノール、2-ブタノール、2-メチルプロパン-1-オール、1-ペンタノール、3-メチルブタン-1-オール、2-メチルブタン-1-オール、2,2-ジメチルプロパン-1-オール、3-ペンタノール、2-ペンタノール、3-メチル-2-ブタノール、1-ヘキサノール、1-ヘプタノールおよび1-オクタノールを含む群より選択される、［1］～［4］のいずれか一つの方法。
［６］ 前記めっき浴中の前記モノヒドロキシアルコールの濃度が0.02ないし12 Mの範囲である、［1］～［5］のいずれか一つの方法。
［７］ 前記めっき浴中の前記モノヒドロキシアルコールの濃度が0.1ないし5 Mの範囲である、［6］の方法。
［８］ 前記白金族金属前駆体は、H ₂ PtCl ₆ 、H ₆ Cl ₂ N ₂ Pt、PtCl ₂ 、PtBr ₂ 、K ₂ [PtCl ₄ ]、Na ₂ [PtCl ₄ ]、Li ₂ [PtCl ₄ ]、H ₂ Pt(OH) ₆ 、Pt(NO ₃ ) ₂ 、[Pt(NH ₃ ) ₄ ]Cl ₂ 、[Pt(NH ₃ ) ₄ ](HCO ₃ ) ₂ 、[Pt(NH ₃ ) ₄ ](OAc) ₂ 、(NH ₃ ) ₄ Pt(NO ₃ ) ₂ 、(NH ₄ ) ₂ PtBr ₆ 、K ₂ PtCl ₆ 、PtSO ₄ 、Pt(HSO ₄ ) ₂ 、Pt(ClO ₄ ) ₂ 、K ₂ PtI ₆ 、K ₂ [Pt(CN) ₄ ]、cis-[Pt(NH ₃ ) ₂ Cl ₂ ]、H ₂ PdCl ₆ 、H ₆ Cl ₂ N ₂ Pd、PdCl ₂ 、PdBr ₂ 、K ₂ [PdCl ₄ ]、Na ₂ [PdCl ₄ ]、Li ₂ [PdCl ₄ ]、H ₂ Pd(OH) ₆ 、Pd(NO ₃ ) ₂ 、[Pd(NH ₃ ) ₄ ]Cl ₂ 、[Pd(NH ₃ ) ₄ ](HCO ₃ ) ₂ 、[Pd(NH ₃ ) ₄ ](OAc) ₂ 、(NH ₄ ) ₂ PdBr ₆ 、(NH ₃ ) ₂ PdCl ₆ 、PdSO ₄ 、Pd(HSO ₄ ) ₂ 、Pd(ClO ₄ ) ₂ 、Pd(OAc) ₂ 、RuCl ₂ ((CH3) ₂ SO) ₄ 、RuCl ₃ 、[Ru(NH ₃ ) ₅ (N ₂ )]Cl ₂ 、Ru(NO ₃ ) ₃ 、RuBr ₃ 、RuF ₃ 、Ru(ClO ₄ ) ₃ 、K ₂ RuCl ₆ 、OsI、OsI ₂ 、OsBr ₃ 、OsCl ₄ 、OsF ₅ 、OsF ₆ 、OsOF ₅ 、OsF ₇ 、IrF ₆ 、IrCl ₃ 、IrF ₄ 、IrF ₅ 、Ir(ClO ₄ ) ₃ 、K ₃ [IrCl ₆ ]、K ₂ [IrCl ₆ ]、Na ₃ [IrCl ₆ ]、Na ₂ [IrCl ₆ ]、Li ₃ [IrCl ₆ ]、Li ₂ [IrCl ₆ ]、[Ir(NH ₃ ) ₄ Cl ₂ ]Cl、RhF ₃ 、RhF ₄ 、RhCl ₃ 、[Rh(NH ₃ ) ₅ Cl]Cl ₂ 、RhCl[P(C ₆ H ₅ ) ₃ ] ₃ 、K[Rh(CO) ₂ Cl ₂ ]、Na[Rh(CO) ₂ Cl ₂ ] Li[Rh(CO) ₂ Cl ₂ ]、Rh ₂ (SO ₄ ) ₃ 、Rh(HSO ₄ ) ₃ 、Rh(ClO ₄ ) ₃ 、これらの水和物ならびにこれらの塩および／または水和物の混合物を含む群から選択される、［1］～［7］のいずれか一つの方法。
［９］ 1以上の白金族金属前駆体の前記還元工程を、異なる金属の1または複数の前駆体の存在下で行い、それによって1以上の白金族金属および異なる金属を含む合金を形成する、［1］～［8］のいずれか一つの方法。
［１０］ 形成した合金は、白金、パラジウム、ロジウム、イリジウム、ルテニウム、オスミウム、金、ニッケルおよび銅を含む群から選択される2以上の金属を含む、［9］の方法。
［１１］ 前記めっき浴中の前記前駆体の濃度は、1 mMないし1 M、好ましくは5 mMないし100 mM、より好ましくは10 mMないし50 mMの範囲である、［1］～［10］のいずれか一つの方法。
［１２］ 前記還元工程を、前記めっき浴の凝固点と沸点との間の温度で行う、［1］～［10］のいずれか一つの方法。
［１３］ 前記還元工程を、-10ないし80℃、好ましくは0ないし40℃、より好ましくは10ないし25℃の温度で行う、［12］の方法。
［１４］ 前記めっき浴はさらに、pH緩衝剤を含む、［1］～［13］のいずれか一つの方法。
［１５］ 前記めっき浴のpHが7未満である、［1］～［14］のいずれか一つの方法。
［１６］ 前記めっき浴の前記pHが3ないし5である、［15］の方法。
［１７］ 前記めっき浴の前記pHが約4である、［16］の方法。
［１８］ 前記基材は、金属、金属合金、ポリマー材料、炭素およびシリコンを含む群から選択される、［1］～［17］のいずれか一つの方法。
［１９］ 前記基材は、白金、パラジウム、ニッケル、金、スチール、鉄－クロム－アルミニウム合金、ナフィオン（登録商標）、ポリエチレン、ポリプロピレン、ポリエチレンテレフタレート、グラファイトおよびシリコンを含む群から選択される、［18］の方法。
［２０］ 前記白金族金属前駆体の還元工程に先立って、前記基材の表面をシーディングする、［1］～［19］のいずれか一つの方法。
［２１］ めっき工程を完了した後、めっきされた基材に高温処理を施す、［1］～［20］のいずれか一つの方法。
［２２］ 前記めっき浴はさらに、光沢剤を含む、［1］～［21］のいずれか一つの方法。
［２３］ 前記めっき浴はさらに、追加の還元剤、好ましくは、ヒドラジンおよびその誘導体、水素化ホウ素または次亜リン酸水素を含む群から選択される還元剤を含む、［1］～［22］のいずれか一つの方法。
［２４］ 前記めっき浴はさらに、2-メチルプロパン-2-オールを含む、［1］～［23］のいずれか一つの方法。
［２５］ 白金族金属およびそれらの合金の無電解析出のためのめっき浴であって、前記めっき浴は、還元剤として、第一級もしくは第二級モノヒドロキシアルコールまたは第一級もしくは第二級モノヒドロキシアルコールの混合物と、1以上の白金族金属前駆体とを含む水溶液である、めっき浴。
［２６］ 前記モノヒドロキシアルコールは下記一般式を有する、［25］のめっき浴。

式中、R ₁ およびR ₂ は同じでも異なっていてもよく、それらの各々は独立に水素原子、直鎖または分枝のC _1-7 -アルキル基、C _3-8 -アリール基、C _4-8 -アラルキル基およびC _4-8 -アルカリール基を含む群より選択される。
［２７］ R ₁ およびR ₂ は独立に、-H、-CH ₃ 、-C ₂ H ₅ 、-C ₃ H ₇ 、-CH(CH ₃ ) ₂ 、-C ₄ H ₉ 、-CH ₂ CH(CH ₃ ) ₂ 、-CH(CH ₃ )C ₂ H ₅ 、-C(CH ₃ ) ₃ 、-C ₅ H ₁₁ 、-CH(CH ₃ )C ₃ H ₇ 、-CH ₂ CH(CH ₃ )C ₂ H ₅ 、-C ₂ H ₄ CH(CH ₃ ) ₂ 、-C(CH ₃ ) ₂ C ₂ H ₅ 、-CH(CH ₃ )CH(CH ₃ ) ₂ 、-CH ₂ C(CH ₃ ) ₃ 、-CH(C ₂ H ₅ ) ₂ 、-C ₆ H ₁₃ 、-C ₇ H ₁₅ 、および-CH(C ₂ H ₅ )(C ₄ H ₉ )を含む群より選択される、［26］のめっき浴。
［２８］ 前記モノヒドロキシアルコールは、メタノール、エタノール、1-プロパノール、2-プロパノール、1-ブタノール、2-ブタノール、2-メチルプロパン-1-オール、1-ペンタノール、3-メチルブタン-1-オール、2-メチルブタン-1-オール、2,2-ジメチルプロパン-1-オール、3-ペンタノール、2-ペンタノール、3-メチル-2-ブタノール、1-ヘキサノール、2-ヘキサノール、2-メチル-1-ペンタノール、3-メチル-1-ペンタノール、4-メチル-1-ペンタノール、3-メチル-2-ペンタノール、4-メチル-2-ペンタノール、2-メチル-3-ペンタノール、2,2-ジメチルブタン-1-オール、2,3-ジメチルブタン-1-オール、3,3-ジメチルブタン-1-オール、3,3-ジメチルブタン-2-オール、2-エチルブタン-1-オール、1-ヘプタノール、2-ヘプタノール、3-ヘプタノール、4-ヘプタノール、1-オクタノール、2-オクタノールおよび2-エチルヘキサン-1-オールを含む群より選択される、［27］のめっき浴。
［２９］ 前記モノヒドロキシアルコールは、メタノール、エタノール、1-プロパノール、2-プロパノール、1-ブタノール、2-ブタノール、2-メチルプロパン-1-オール、1-ペンタノール、3-メチルブタン-1-オール、2-メチルブタン-1-オール、2,2-ジメチルプロパン-1-オール、3-ペンタノール、2-ペンタノール、3-メチル-2-ブタノール、1-ヘキサノール、1-ヘプタノールおよび1-オクタノールを含む群より選択される、［28］のめっき浴。
［３０］ 前記モノヒドロキシアルコールの濃度が0.02ないし12 Mの範囲、好ましくは0.1ないし5 Mの範囲である、［25］～［29］のいずれか一つのめっき浴。
［３１］ さらに、追加の還元剤、好ましくは、ヒドラジンおよびその誘導体、水素化ホウ素または次亜リン酸水素を含む群から選択される還元剤を含む、［25］～［30］のいずれか一つのめっき浴。
［３２］ 前記白金族金属前駆体は、H ₂ PtCl ₆ 、H ₆ Cl ₂ N ₂ Pt、PtCl ₂ 、PtBr ₂ 、K ₂ [PtCl ₄ ]、Na ₂ [PtCl ₄ ]、Li ₂ [PtCl ₄ ]、H ₂ Pt(OH) ₆ 、Pt(NO ₃ ) ₂ 、[Pt(NH ₃ ) ₄ ]Cl ₂ 、[Pt(NH ₃ ) ₄ ](HCO ₃ ) ₂ 、[Pt(NH ₃ ) ₄ ](OAc) ₂ 、(NH ₃ ) ₄ Pt(NO ₃ ) ₂ 、(NH ₄ ) ₂ PtBr ₆ 、K ₂ PtCl ₆ 、PtSO ₄ 、Pt(HSO ₄ ) ₂ 、Pt(ClO ₄ ) ₂ 、K ₂ PtI ₆ 、K ₂ [Pt(CN) ₄ ]、cis-[Pt(NH ₃ ) ₂ Cl ₂ ]、H ₂ PdCl ₆ 、H ₆ Cl ₂ N ₂ Pd、PdCl ₂ 、PdBr ₂ 、K ₂ [PdCl ₄ ]、Na ₂ [PdCl ₄ ]、Li ₂ [PdCl ₄ ]、H ₂ Pd(OH) ₆ 、Pd(NO ₃ ) ₂ 、[Pd(NH ₃ ) ₄ ]Cl ₂ 、[Pd(NH ₃ ) ₄ ](HCO ₃ ) ₂ 、[Pd(NH ₃ ) ₄ ](OAc) ₂ 、(NH ₄ ) ₂ PdBr ₆ 、(NH ₃ ) ₂ PdCl ₆ 、PdSO ₄ 、Pd(HSO ₄ ) ₂ 、Pd(ClO ₄ ) ₂ 、Pd(OAc) ₂ 、RuCl ₂ ((CH3) ₂ SO) ₄ 、RuCl ₃ 、[Ru(NH ₃ ) ₅ (N ₂ )]Cl ₂ 、Ru(NO ₃ ) ₃ 、RuBr ₃ 、RuF ₃ 、Ru(ClO ₄ ) ₃ 、K ₂ RuCl ₆ 、OsI、OsI ₂ 、OsBr ₃ 、OsCl ₄ 、OsF ₅ 、OsF ₆ 、OsOF ₅ 、OsF ₇ 、IrF ₆ 、IrCl ₃ 、IrF ₄ 、IrF ₅ 、Ir(ClO ₄ ) ₃ 、K ₃ [IrCl ₆ ]、K ₂ [IrCl ₆ ]、Na ₃ [IrCl ₆ ]、Na ₂ [IrCl ₆ ]、Li ₃ [IrCl ₆ ]、Li ₂ [IrCl ₆ ]、[Ir(NH ₃ ) ₄ Cl ₂ ]Cl、RhF ₃ 、RhF ₄ 、RhCl ₃ 、[Rh(NH ₃ ) ₅ Cl]Cl ₂ 、RhCl[P(C ₆ H ₅ ) ₃ ] ₃ 、K[Rh(CO) ₂ Cl ₂ ]、Na[Rh(CO) ₂ Cl ₂ ] Li[Rh(CO) ₂ Cl ₂ ]、Rh ₂ (SO ₄ ) ₃ 、Rh(HSO ₄ ) ₃ 、Rh(ClO ₄ ) ₃ 、これらの水和物ならびにこれらの塩および／または水和物の混合物を含む群から選択される、［25］～［31］のいずれか一つのめっき浴。
［３３］ 前記前駆体の濃度が、1 mMないし1 Mの範囲である、［25］～［32］のいずれか一つのめっき浴。
［３４］ 前記前駆体の濃度が、5 mMないし100 mMの範囲である、［33］のめっき浴。
［３５］ 前記前駆体の濃度が、10 mMないし50 mMの範囲である、［34］のめっき浴。
［３６］ 前記めっき浴のpHが7未満である、［25］～［36］のいずれか一つのめっき浴。
［３７］ 前記pHが3ないし5である、［36］のめっき浴。
［３８］ 前記めっき浴の前記pHが約4である、［37］のめっき浴。
［３９］ さらに、pH緩衝剤を含む、［25］～［21］のいずれか一つの方法。
［４０］ さらに、光沢剤を含む、［25］～［39］のいずれか一つのめっき浴。
［４１］ さらに、2-メチルプロパン-2-オールを含む、［25］～［40］のいずれか一つのめっき浴。
［４２］ ［25］～［41］のいずれか一つに規定しためっき浴の、白金族金属の無電解析出における使用。 Representative results are shown in Fig. 11, which are Pt _- Ir alloy precipitates obtained with different reducing agents in 0.5 mol dm ^-3 _H2SO4 and 0.5 mol dm ^-3 ethanol. Recorded voltammograms are shown: gray - ethanol; black - butanol. Voltamograms were recorded at a scan rate of 5 mV s-1 and currents were normalized to geometric area. As shown in FIG. 11, the electrolessly deposited layers were found to be highly active for ethanol oxidation, both in terms of onset potential and relative voltamoperometric current for ethanol oxidation. The most active layers were deposited by using ethanol and butanol as reducing agents. As noted above, these reducing agents significantly promote surface roughness, which in turn increases oxidation current.
The invention described in the claims as originally filed will be added below.
[1] A method for electroless deposition of platinum group metals and alloys thereof from a plating bath onto a substrate, comprising a step of reducing one or more platinum group metal precursors with a reducing agent, said reducing agent comprising: A method that is a primary or secondary monohydroxy alcohol or a mixture of primary or secondary monohydroxy alcohols.
[2] The method of [1], wherein the monohydroxy alcohol has the following general formula.

wherein R ₁ and R ₂ may be the same or different and each of them independently represents a hydrogen atom, a linear or branched C _1-7 -alkyl group, a C _3-8 -aryl group, a C ₄ is selected from the group comprising _-8 -aralkyl and _C4-8 -alkaryl groups;
[3 _{] R1} and _{R2 are independently} -H , _-CH3 , _-C2H5 , -C3H7 , _-CH ( _CH3 ) ₂ , -C4H9 , _{-CH2CH (} CH3 ) ₂ , -CH ( _CH3 ) _{C2H5 ,} -C ( _CH3 ) ₃ , -C5H11 _{, -CH} ( _CH3 ) _{C3H7 , -CH2CH ( CH3} ) C 2H5 _, -C2H4CH ₍ CH3 ) ₂ , -C _{( CH3} ) _{2C2H5 ,} -CH _{( CH3} ) CH _{( CH3} ) ₂ , -CH2C ( _CH3 ) _{3 _ _} , -CH ₍ C2H5 ) ₂ , _-C6H13 , _{-C7H15 ,} and -CH _{( C2H5 ) (} C4H9 ) [ _{1 ]} or [2] method.
[4] The monohydroxy alcohol is methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methylpropan-1-ol, 1-pentanol, 3-methylbutan-1-ol. , 2-methylbutan-1-ol, 2,2-dimethylpropan-1-ol, 3-pentanol, 2-pentanol, 3-methyl-2-butanol, 1-hexanol, 2-hexanol, 2-methyl- 1-pentanol, 3-methyl-1-pentanol, 4-methyl-1-pentanol, 3-methyl-2-pentanol, 4-methyl-2-pentanol, 2-methyl-3-pentanol, 2,2-dimethylbutan-1-ol, 2,3-dimethylbutan-1-ol, 3,3-dimethylbutan-1-ol, 3,3-dimethylbutan-2-ol, 2-ethylbutan-1-ol of [1] to [3] selected from the group comprising ol, 1-heptanol, 2-heptanol, 3-heptanol, 4-heptanol, 1-octanol, 2-octanol and 2-ethylhexan-1-ol any one method.
[5] The monohydroxy alcohol is methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methylpropan-1-ol, 1-pentanol, 3-methylbutan-1-ol. , 2-methylbutan-1-ol, 2,2-dimethylpropan-1-ol, 3-pentanol, 2-pentanol, 3-methyl-2-butanol, 1-hexanol, 1-heptanol and 1-octanol The method of any one of [1] to [4], selected from the group comprising.
[6] The method of any one of [1] to [5], wherein the monohydroxy alcohol concentration in the plating bath is in the range of 0.02 to 12M.
[7] The method of [6], wherein the monohydroxy alcohol concentration in the plating bath is in the range of 0.1 to 5M.
[ ₈ ] _{The platinum} group metal precursors are _{H2PtCl6 ,} H6Cl2N2Pt _, PtCl2 , _PtBr2 , K2 _[ PtCl4 ] , Na2 [ PtCl4 _] , _{Li2 [ PtCl4 ]} , H2Pt(OH) ₆ , Pt(NO3 ) ₂ , [Pt(NH3 ₎ 4 _] Cl2 _, [Pt(NH3 ₎ 4 _] (HCO3 ₎ 2 _, [Pt _{( NH3} ) ₄ ] ₍ OAc) ₂ , _{( NH3} ) _{4Pt (} NO3 ) _{2 , (} NH4 ) _{2PtBr6 , K2PtCl6} , _PtSO4 , Pt ₍ HSO4 ) ₂ , Pt _{( ClO4} ) ₂ , K2PtI6 , K2 _[ Pt ₍ CN) ₄ ] , cis- [ _{Pt ( NH3} ) _2Cl2 ] , _H2PdCl6 , H6Cl2N2Pd , _{PdCl2 ,} PdBr2 , _K2 [ _{PdCl4 ] ,} Na2[PdCl4 ] , Li2 [PdCl4 _] , _H2Pd (OH) ₆ , Pd ₍ NO3 ) ₂ , [Pd(NH3 _{)4 ]} Cl2 _, [ _Pd ( _{NH3 )} 4 _{] (} HCO ₃ ) ₂ , [Pd(NH3 _{) 4} ] _{( OAc} ) ₂ , (NH4 ₎ 2PdBr6 , (NH3 ₎ 2PdCl6 _, PdSO4 _, Pd( _HSO4 ) 2 _, Pd _{( ClO4} ) ₂ , Pd(OAc) ₂ , RuCl2 ₍ (CH3) _2SO ) ₄ , RuCl3 , [Ru(NH3 ₎ 5 ₍ N2 )]Cl2 _, Ru(NO3 ₎ 3 _, RuBr3 _{, RuF3 , Ru} ( ClO4 ) ₃ , _K2RuCl6 , _OsI , OsI2 , _OsBr3 , _OsCl4 , OsF5 _{, OsF6} , _OsOF5 , OsF7 , _IrF6 , IrCl3 , _{IrF4 , IrF5} , _{Ir ( ClO4 ) 3} , K3[IrCl6 _] , K2 [IrCl6 _] , _Na3 [IrCl6 _] , _Na2 [ _IrCl6 ], _Li3 [ _IrCl6 ], Li2 [IrCl6 _{] ,} [ _{Ir ( NH3} ) _4Cl2 ]Cl, RhF3 , _{RhF4 ,} RhCl3 , [Rh(NH3 ₎ 5Cl _] Cl2 _, RhCl [P( _{C6H5 )} 3 _] 3 _{, K} [ Rh ₍ CO) _2Cl2 ], Na[Rh(CO) _2Cl2 ] Li[Rh(CO) _{2Cl2 ]} , Rh2 ₍ SO4 ) ₃ , Rh ₍ HSO4 ) _{3 , Rh} ( _ClO4 ) _{3 ,} The method according to any one of [1] to [7], which is selected from the group containing hydrates thereof and mixtures of salts and/or hydrates thereof.
[9] performing said reduction step of one or more platinum group metal precursors in the presence of one or more precursors of different metals, thereby forming an alloy comprising one or more platinum group metals and a different metal; Any one method of [1] to [8].
[10] The method of [9], wherein the alloy formed comprises two or more metals selected from the group comprising platinum, palladium, rhodium, iridium, ruthenium, osmium, gold, nickel and copper.
[11] the concentration of the precursor in the plating bath is in the range of 1 mM to 1 M, preferably 5 mM to 100 mM, more preferably 10 mM to 50 mM; any one method.
[12] The method according to any one of [1] to [10], wherein the reducing step is performed at a temperature between the freezing point and the boiling point of the plating bath.
[13] The method of [12], wherein the reduction step is carried out at a temperature of -10 to 80°C, preferably 0 to 40°C, more preferably 10 to 25°C.
[14] The method according to any one of [1] to [13], wherein the plating bath further contains a pH buffer.
[15] The method according to any one of [1] to [14], wherein the plating bath has a pH of less than 7.
[16] The method of [15], wherein the pH of the plating bath is 3-5.
[17] The method of [16], wherein the pH of the plating bath is about 4.
[18] The method of any one of [1] to [17], wherein the substrate is selected from the group including metals, metal alloys, polymeric materials, carbon and silicon.
[19] The substrate is selected from the group comprising platinum, palladium, nickel, gold, steel, iron-chromium-aluminum alloy, Nafion®, polyethylene, polypropylene, polyethylene terephthalate, graphite and silicon, [ 18] method.
[20] The method of any one of [1] to [19], wherein the surface of the substrate is seeded prior to the step of reducing the platinum group metal precursor.
[21] The method of any one of [1]-[20], wherein after completing the plating step, the plated substrate is subjected to a high temperature treatment.
[22] The method according to any one of [1] to [21], wherein the plating bath further contains a brightener.
[23] The plating bath further comprises an additional reducing agent, preferably a reducing agent selected from the group comprising hydrazine and its derivatives, borohydride or hydrogen hypophosphite [1]-[22] any one method.
[24] The method of any one of [1] to [23], wherein the plating bath further contains 2-methylpropan-2-ol.
[25] A plating bath for electroless deposition of platinum group metals and alloys thereof, said plating bath comprising, as a reducing agent, a primary or secondary monohydroxy alcohol or a primary or secondary A plating bath that is an aqueous solution comprising a mixture of monohydroxy alcohols and one or more platinum group metal precursors.
[26] The plating bath of [25], wherein the monohydroxy alcohol has the following general formula.

wherein R ₁ and R ₂ may be the same or different and each of them independently represents a hydrogen atom, a linear or branched C _1-7 -alkyl group, a C _3-8 -aryl group, a C ₄ is selected from the group comprising _-8 -aralkyl and _C4-8 -alkaryl groups;
[ 27] _R1 and _{R2 are independently} -H , _-CH3 , _-C2H5 , -C3H7 , _-CH ( _CH3 ) _{2 ,} -C4H9 , _{-CH2CH (} CH3 ) ₂ , -CH ( _CH3 ) _{C2H5 ,} -C ( _CH3 ) ₃ , -C5H11 _{, -CH} ( _CH3 ) _{C3H7 , -CH2CH ( CH3} ) C 2H5 _, -C2H4CH ₍ CH3 ) ₂ , -C _{( CH3} ) _{2C2H5 ,} -CH _{( CH3} ) CH _{( CH3} ) ₂ , -CH2C ( _CH3 ) _{3 _ _} , -CH ₍ C2H5 ) ₂ , _-C6H13 , _-C7H15 , and _{-CH ( C2H5 ) (} C4H9 ) _of [ ₂₆ ] . plating bath.
[28] The monohydroxy alcohol is methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methylpropan-1-ol, 1-pentanol, 3-methylbutan-1-ol. , 2-methylbutan-1-ol, 2,2-dimethylpropan-1-ol, 3-pentanol, 2-pentanol, 3-methyl-2-butanol, 1-hexanol, 2-hexanol, 2-methyl- 1-pentanol, 3-methyl-1-pentanol, 4-methyl-1-pentanol, 3-methyl-2-pentanol, 4-methyl-2-pentanol, 2-methyl-3-pentanol, 2,2-dimethylbutan-1-ol, 2,3-dimethylbutan-1-ol, 3,3-dimethylbutan-1-ol, 3,3-dimethylbutan-2-ol, 2-ethylbutan-1-ol The plating bath of [27] selected from the group comprising ol, 1-heptanol, 2-heptanol, 3-heptanol, 4-heptanol, 1-octanol, 2-octanol and 2-ethylhexan-1-ol.
[29] The monohydroxy alcohol is methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methylpropan-1-ol, 1-pentanol, 3-methylbutan-1-ol. , 2-methylbutan-1-ol, 2,2-dimethylpropan-1-ol, 3-pentanol, 2-pentanol, 3-methyl-2-butanol, 1-hexanol, 1-heptanol and 1-octanol The plating bath of [28], selected from the group comprising:
[30] The plating bath of any one of [25]-[29], wherein the concentration of the monohydroxy alcohol is in the range of 0.02 to 12M, preferably in the range of 0.1 to 5M.
[31] Any one of [25] to [30], further comprising an additional reducing agent, preferably a reducing agent selected from the group containing hydrazine and its derivatives, borohydride or hydrogen hypophosphite two plating baths.
[ 32 ] _{The platinum} group metal precursors are _{H2PtCl6 ,} H6Cl2N2Pt _, PtCl2 , _PtBr2 , _K2 [ PtCl4 _{] ,} Na2 _[ PtCl4 ] , _Li2 [ _{PtCl4 ]} , H2Pt(OH) ₆ , Pt(NO3 ) ₂ , [Pt(NH3 ₎ 4 _] Cl2 _, [Pt(NH3 ₎ 4 _] (HCO3 ₎ 2 _, [Pt _{( NH3} ) ₄ ] ₍ OAc) ₂ , _{( NH3} ) _{4Pt (} NO3 ) _{2 , (} NH4 ) _{2PtBr6 , K2PtCl6} , _PtSO4 , Pt ₍ HSO4 ) ₂ , Pt _{( ClO4} ) ₂ , K2PtI6 , K2 _[ Pt ₍ CN) ₄ ] , cis- [ _{Pt ( NH3} ) _2Cl2 ] , _H2PdCl6 , H6Cl2N2Pd , _{PdCl2 ,} PdBr2 , _K2 [ _{PdCl4 ] ,} Na2[PdCl4 ] , Li2 [PdCl4 _] , _H2Pd (OH) ₆ , Pd ₍ NO3 ) ₂ , [Pd(NH3 _{)4 ]} Cl2 _, [ _Pd ( _{NH3 )} 4 _{] (} HCO ₃ ) ₂ , [Pd(NH3 _{) 4} ] _{( OAc} ) ₂ , (NH4 ₎ 2PdBr6 , (NH3 ₎ 2PdCl6 _, PdSO4 _, Pd( _HSO4 ) 2 _, Pd _{( ClO4} ) ₂ , Pd(OAc) ₂ , RuCl2 ₍ (CH3) _2SO ) ₄ , RuCl3 , [Ru(NH3 ₎ 5 ₍ N2 )]Cl2 _, Ru(NO3 ₎ 3 _, RuBr3 _{, RuF3 , Ru} ( ClO4 ) ₃ , _K2RuCl6 , _OsI , OsI2 , _OsBr3 , _OsCl4 , OsF5 _{, OsF6} , _OsOF5 , OsF7 , _IrF6 , IrCl3 , _{IrF4 , IrF5} , _{Ir ( ClO4 ) 3} , K3[IrCl6 _] , K2 [IrCl6 _] , _Na3 [IrCl6 _] , _Na2 [ _IrCl6 ], _Li3 [ _IrCl6 ], Li2 [IrCl6 _{] ,} [ _{Ir ( NH3} ) _4Cl2 ]Cl, RhF3 , _{RhF4 ,} RhCl3 , [Rh(NH3 ₎ 5Cl _] Cl2 _{, RhCl} [ P( _{C6H5 )} 3 _] 3 _{, K} [ Rh (CO) _2Cl2 ], Na[Rh(CO) _2Cl2 ] Li[Rh(CO) _{2Cl2 ]} , Rh2 ₍ SO4 ) _{3 ,} Rh ₍ HSO4 ) _{3 , Rh} ( _ClO4 ) ₃ , hydrates thereof and mixtures of salts and/or hydrates thereof, the plating bath of any one of [25] to [31].
[33] The plating bath of any one of [25]-[32], wherein the concentration of the precursor ranges from 1 mM to 1M.
[34] The plating bath of [33], wherein the precursor concentration is in the range of 5 mM to 100 mM.
[35] The plating bath of [34], wherein the precursor concentration is in the range of 10 mM to 50 mM.
[36] The plating bath according to any one of [25] to [36], wherein the plating bath has a pH of less than 7.
[37] The plating bath of [36], wherein the pH is 3-5.
[38] The plating bath of [37], wherein said pH of said plating bath is about 4.
[39] The method of any one of [25] to [21], further comprising a pH buffer.
[40] The plating bath of any one of [25] to [39], further comprising a brightener.
[41] The plating bath of any one of [25] to [40], further containing 2-methylpropan-2-ol.
[42] Use of the plating bath defined in any one of [25] to [41] for electroless deposition of platinum group metals.

Claims (32)

1. A method for electroless deposition of platinum from a plating bath onto a substrate comprising a step of reducing one or more platinum precursors with a reducing agent, said reducing agent being methanol, ethanol, 1-propanol, 2-propanol. and a monohydroxy alcohol selected from the group consisting of 2-butanol . 2. The method of claim 1, wherein the concentration of said monohydroxy alcohol in said plating bath ranges from 0.02 to 12M. 3. The method of claim 2 , wherein the concentration of said monohydroxy alcohol in said plating bath ranges from 0.1 to 5M. The _one or _more platinum precursors _{are H2PtCl6} , _H6Cl2N2Pt , _PtCl2 , _PtBr2 , K2[ _PtCl4 ], _Na2 [ _PtCl4 ], _Li2 [ _{PtCl4 ]} , H 2Pt(OH) ₆ , Pt( _NO3 ) ₂ , [Pt( _NH3 ) ₄ ] _Cl2 , [Pt( _NH3 ) ₄ ]( _HCO3 ) ₂ , [Pt( _NH3 ) ₄ ] ₍ OAc) ₂ , ( _NH3 ) _4Pt ( _NO3 ) ₂ , ₍ NH4) _2PtBr6 , _K2PtCl6 , _PtSO4 , Pt _{( HSO4} ) ₂ , _{Pt ( ClO4} ) ₂ , _K2PtI6 , K ₂ selected from the group comprising [Pt(CN) ₄ ], cis-[Pt _{( NH3} ) _2Cl2 ], hydrates thereof and mixtures of salts and/or hydrates thereof; - The method of any one of 3 . 5. Any one of claims 1-4 , wherein the concentration of said platinum precursor in said plating bath ranges from 1 mM to 1 M, preferably from 5 mM to 100 mM, more preferably from 10 mM to 50 mM. the method of. 6. The method of any one of claims 1-5 , wherein the reducing step is performed at a temperature between the freezing point and the boiling point of the plating bath. 7. The method of claim 6 , wherein said reduction step is carried out at a temperature of -10 to 80°C, preferably 0 to 40°C, more preferably 10 to 25°C. 8. The method of any one of claims 1-7 , wherein the plating bath further comprises a pH buffer. 9. The method of any one of claims 1-8 , wherein the plating bath has a pH of less than 7. 10. The method of claim 9 , wherein said pH of said plating bath is 3-5. 11. The method of claim 10 , wherein said pH of said plating bath is 4. 12. The method of any one of claims 1-11 , wherein the substrate is selected from the group comprising metals, metal alloys, polymeric materials, carbon and silicon. 13. The substrate of claim 12 , wherein said substrate is selected from the group comprising platinum, palladium, nickel, gold, steel, iron-chromium-aluminum alloy, Nafion®, polyethylene, polypropylene, polyethylene terephthalate, graphite and silicon. Method. 14. The method of any one of claims 1-13 , wherein the surface of the substrate is seeded prior to the step of reducing the platinum precursor. 15. The method of any one of claims 1-14 , wherein after completing the plating step, the plated substrate is subjected to a high temperature treatment performed at a temperature of 700-1000<0>C or flame annealed. 16. The method of any one of claims 1-15 , wherein the plating bath further comprises a brightener. 17. Any one of claims 1-16 , wherein the plating bath further comprises an additional reducing agent, preferably selected from the group comprising hydrazine and its derivatives, borohydride or hydrogen hypophosphite. the method of. 18. The method of any one of claims 1-17 , wherein the plating bath further comprises 2-methylpropan-2-ol. A plating bath for electroless deposition of platinum, said plating bath comprising a monohydroxy alcohol selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol and 2-butanol as a reducing agent. , and one or more platinum precursors. 20. The plating bath of claim 19, wherein the concentration of said monohydroxy alcohol is in the range 0.02 to 12M, preferably in the range 0.1 to 5M. 21. The plating bath of claim 19 or 20 , further comprising an additional reducing agent, preferably selected from the group comprising hydrazine and its derivatives, borohydride or hydrogen hypophosphite. The _one or _more platinum precursors _{are H2PtCl6} , _H6Cl2N2Pt , _PtCl2 , _PtBr2 , K2[ _PtCl4 ], _Na2 [ _PtCl4 ], _Li2 [ _{PtCl4 ]} , H 2Pt(OH) ₆ , Pt( _NO3 ) ₂ , [Pt( _NH3 ) ₄ ] _Cl2 , [Pt( _NH3 ) ₄ ]( _HCO3 ) ₂ , [Pt( _NH3 ) ₄ ] ₍ OAc) ₂ , ( _NH3 ) _4Pt ( _NO3 ) ₂ , ₍ NH4) _2PtBr6 , _K2PtCl6 , _PtSO4 , Pt _{( HSO4} ) ₂ , _{Pt ( ClO4} ) ₂ , _K2PtI6 , K ₂₀ selected from the group comprising ₂ [Pt(CN) ₄ ], cis- [Pt( _NH3 ) _2Cl2 ], hydrates thereof and mixtures of salts and/or hydrates thereof; The plating bath of any one of -21 . 23. The plating bath of any one of claims 19-22 , wherein the concentration of said precursor ranges from 1 mM to 1M. 24. The plating bath of claim 23 , wherein the precursor concentration ranges from 5 mM to 100 mM. 25. The plating bath of claim 24 , wherein the precursor concentration ranges from 10 mM to 50 mM. 26. The plating bath of any one of claims 19-25 , wherein the plating bath has a pH of less than 7. 27. The plating bath of claim 26 , wherein said pH is 3-5. 28. The plating bath of claim 27 , wherein said pH of said plating bath is 4. 29. The plating bath of any one of claims 19-28 , further comprising a pH buffer. 30. The plating bath of any one of claims 19-29 , further comprising a brightener. 31. The plating bath of any one of claims 19-30, further comprising 2-methylpropan-2-ol. Use of a plating bath as defined in any one of claims 19-31 for the electroless deposition of platinum.

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