GB2070038A - Method of Producing Semi- conducting N4-chelate Electrode Coating - Google Patents
Method of Producing Semi- conducting N4-chelate Electrode Coating Download PDFInfo
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- GB2070038A GB2070038A GB8006230A GB8006230A GB2070038A GB 2070038 A GB2070038 A GB 2070038A GB 8006230 A GB8006230 A GB 8006230A GB 8006230 A GB8006230 A GB 8006230A GB 2070038 A GB2070038 A GB 2070038A
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- chelate
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- 238000000576 coating method Methods 0.000 title claims abstract description 63
- 239000013522 chelant Substances 0.000 title claims abstract description 56
- 239000011248 coating agent Substances 0.000 title claims abstract description 49
- 238000000034 method Methods 0.000 title claims description 23
- 229910052751 metal Inorganic materials 0.000 claims abstract description 49
- 239000002184 metal Substances 0.000 claims abstract description 49
- 238000006243 chemical reaction Methods 0.000 claims abstract description 29
- 150000001875 compounds Chemical class 0.000 claims abstract description 11
- 238000011065 in-situ storage Methods 0.000 claims abstract description 10
- 238000007669 thermal treatment Methods 0.000 claims abstract description 10
- NLDYACGHTUPAQU-UHFFFAOYSA-N tetracyanoethylene Chemical group N#CC(C#N)=C(C#N)C#N NLDYACGHTUPAQU-UHFFFAOYSA-N 0.000 claims abstract description 9
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 6
- 239000010936 titanium Substances 0.000 claims description 6
- 229910052719 titanium Inorganic materials 0.000 claims description 6
- 125000004122 cyclic group Chemical group 0.000 claims description 3
- 230000006866 deterioration Effects 0.000 claims description 3
- 229910044991 metal oxide Inorganic materials 0.000 claims description 2
- 150000004706 metal oxides Chemical class 0.000 claims description 2
- 230000003647 oxidation Effects 0.000 claims description 2
- 238000007254 oxidation reaction Methods 0.000 claims description 2
- 230000001681 protective effect Effects 0.000 claims 2
- 229910001069 Ti alloy Inorganic materials 0.000 claims 1
- 229910001092 metal group alloy Inorganic materials 0.000 claims 1
- 239000000758 substrate Substances 0.000 abstract description 26
- 238000000151 deposition Methods 0.000 abstract description 4
- 238000004519 manufacturing process Methods 0.000 description 8
- 150000002739 metals Chemical class 0.000 description 8
- 239000007858 starting material Substances 0.000 description 8
- 230000015572 biosynthetic process Effects 0.000 description 6
- 230000003197 catalytic effect Effects 0.000 description 6
- 229910052799 carbon Inorganic materials 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 4
- 238000011835 investigation Methods 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 3
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 3
- 239000002253 acid Substances 0.000 description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 3
- 239000010949 copper Substances 0.000 description 3
- 230000008021 deposition Effects 0.000 description 3
- 239000000446 fuel Substances 0.000 description 3
- 239000011521 glass Substances 0.000 description 3
- 229910021645 metal ion Inorganic materials 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
- 239000001301 oxygen Substances 0.000 description 3
- 238000002360 preparation method Methods 0.000 description 3
- 230000009467 reduction Effects 0.000 description 3
- 150000003839 salts Chemical class 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 description 2
- 229910000831 Steel Inorganic materials 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
- 229910045601 alloy Inorganic materials 0.000 description 2
- 230000015556 catabolic process Effects 0.000 description 2
- 230000009920 chelation Effects 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 238000004132 cross linking Methods 0.000 description 2
- 238000006731 degradation reaction Methods 0.000 description 2
- 238000005238 degreasing Methods 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- NJSUFZNXBBXAAC-UHFFFAOYSA-N ethanol;toluene Chemical compound CCO.CC1=CC=CC=C1 NJSUFZNXBBXAAC-UHFFFAOYSA-N 0.000 description 2
- 238000007654 immersion Methods 0.000 description 2
- 229910052742 iron Inorganic materials 0.000 description 2
- 150000002736 metal compounds Chemical class 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 229910052759 nickel Inorganic materials 0.000 description 2
- 239000012071 phase Substances 0.000 description 2
- 230000002035 prolonged effect Effects 0.000 description 2
- 239000011253 protective coating Substances 0.000 description 2
- 238000007789 sealing Methods 0.000 description 2
- 238000010583 slow cooling Methods 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- 235000011149 sulphuric acid Nutrition 0.000 description 2
- 238000003786 synthesis reaction Methods 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 239000012808 vapor phase Substances 0.000 description 2
- KSXHZOTTWSNEHY-UHFFFAOYSA-N 3-[3-(2-cyanoethoxy)-2,2-bis(2-cyanoethoxymethyl)propoxy]propanenitrile Chemical group N#CCCOCC(COCCC#N)(COCCC#N)COCCC#N KSXHZOTTWSNEHY-UHFFFAOYSA-N 0.000 description 1
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 1
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- 230000001464 adherent effect Effects 0.000 description 1
- 125000003118 aryl group Chemical group 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 229910017052 cobalt Inorganic materials 0.000 description 1
- 239000010941 cobalt Substances 0.000 description 1
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 1
- 230000000295 complement effect Effects 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical group O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 description 1
- 239000002019 doping agent Substances 0.000 description 1
- 239000003792 electrolyte Substances 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- ZXDVJTCKSXUPAH-UHFFFAOYSA-N furan-2,3,4,5-tetracarbonitrile Chemical compound N#CC=1OC(C#N)=C(C#N)C=1C#N ZXDVJTCKSXUPAH-UHFFFAOYSA-N 0.000 description 1
- 238000010574 gas phase reaction Methods 0.000 description 1
- 230000007062 hydrolysis Effects 0.000 description 1
- 238000006460 hydrolysis reaction Methods 0.000 description 1
- 238000005286 illumination Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000003446 ligand Substances 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 239000011572 manganese Substances 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- QYPMXQAQOCDEKF-UHFFFAOYSA-N naphthalene-1,2,3,4-tetracarbonitrile Chemical compound C1=CC=CC2=C(C#N)C(C#N)=C(C#N)C(C#N)=C21 QYPMXQAQOCDEKF-UHFFFAOYSA-N 0.000 description 1
- 229910052758 niobium Inorganic materials 0.000 description 1
- IEQIEDJGQAUEQZ-UHFFFAOYSA-N phthalocyanine Chemical compound N1C(N=C2C3=CC=CC=C3C(N=C3C4=CC=CC=C4C(=N4)N3)=N2)=C(C=CC=C2)C2=C1N=C1C2=CC=CC=C2C4=N1 IEQIEDJGQAUEQZ-UHFFFAOYSA-N 0.000 description 1
- -1 platinum group metals Chemical class 0.000 description 1
- 238000005498 polishing Methods 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000004886 process control Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- VOHLAVUPSKBRPU-UHFFFAOYSA-N pyrazine-2,3,5,6-tetracarbonitrile Chemical compound N#CC1=NC(C#N)=C(C#N)N=C1C#N VOHLAVUPSKBRPU-UHFFFAOYSA-N 0.000 description 1
- CYEWTOYRKOTLHG-UHFFFAOYSA-N pyridine-2,3,4,5-tetracarbonitrile Chemical compound N#CC1=CN=C(C#N)C(C#N)=C1C#N CYEWTOYRKOTLHG-UHFFFAOYSA-N 0.000 description 1
- 238000005488 sandblasting Methods 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 150000003457 sulfones Chemical class 0.000 description 1
- 229910052715 tantalum Inorganic materials 0.000 description 1
- OLFGLXNMFYJMRN-UHFFFAOYSA-N thiophene-2,3,4,5-tetracarbonitrile Chemical compound N#CC=1SC(C#N)=C(C#N)C=1C#N OLFGLXNMFYJMRN-UHFFFAOYSA-N 0.000 description 1
- 229910052721 tungsten Inorganic materials 0.000 description 1
- 229910052726 zirconium Inorganic materials 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D1/00—Processes for applying liquids or other fluent materials
- B05D1/60—Deposition of organic layers from vapour phase
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B1/00—Electrolytic production of inorganic compounds or non-metals
- C25B1/50—Processes
- C25B1/55—Photoelectrolysis
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
- C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
- C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
- C25B11/073—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material
- C25B11/075—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of a single catalytic element or catalytic compound
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Manufacturing Of Electric Cables (AREA)
- Inert Electrodes (AREA)
- Hybrid Cells (AREA)
- Electrodes For Compound Or Non-Metal Manufacture (AREA)
Abstract
A semi-conducting, stable polychelate coating is manufactured in situ on a conducting electrode substrate providing metal coordination centres, by depositing from the vapour phase a tetranitrile compound (e.g. tetracyanobenzene or tetracyanoethylene) so that a predetermined specific amount is deposited per unit substrate area and carrying out a controlled chelating reaction and thermal treatment on the substrate surface. The temperature and duration as well as the specific amount are selected to form a uniform, cross-linked, polychelate coating coordinated to metal sites on the surface as an N4-chelate.
Description
SPECIFICATION
Method of Producing Semi-conducting N4
Chelate Electrode Coating (MPC)
The invention generally relates to semiconducting N4-chelate electrode coatings and their manufacture.
State of the Art
N4-chelates and more particularly metal phthalocyanines are known to exhibit interesting catalytic properties, especially for oxygen reduction in fuel cells.
Publications on this subject may be illustrated for example by:
V.S. Bagotzsky et al in the Journal of Power
Sources 2 (1977/78)233-240 H. Meier et al in Berichte der
Bunsengesellschaft Bd 77, Nr 10/11, 1973 U.S. Patents Nos: 3,585,079; 4,1 79,350 Background of the Invention
Aromatic 1.2 dinitriles such as 0phthalodinitriile (DCB) react with metal salts and metal powders such as copper, iron, nickel, cobalt and manganese to form phthalocyanines. It is also possible to form films of monomeric phthalocyanine on a copper plate by a gas phase reaction of the dinitrile vapour.
On the other hand, when tetracyano compounds are used, polymeric phthalocyanines of different molecular weights may be formed, depending on the reaction conditions.
Polymeric films are obtained after prolonged exposure of metal plates to tetracyanoethylene (TCNE) at elevated temperatures. Monomeric and polymeric phthalocyanines exhibit interesting electronic, electrocatalytic and photoelectrochemical properties Eley and
Vartanyian found in 1948 that the conductivity of phthalocyanines increases expenentially with temperature in the form of a Boltzmann distribution, which is typical for so-called intrinsic semiconductors.
Since then there have been a series of publications relating to investigations of the influence of the conditions of preparation on the conductivity of monomeric and polymeric phthalocyanines.
It has been found that polymeric phthalocyanines may have semi-conducting properties of the n or p type, depending on the conditions of preparation.
N4-chelates can catalyze the cathodic reduction of oxygen.
Phthalocyanines of high molecular weight are particularly resistant and insoluble in acid media.
Acid electrolytes are preferred for fuel cells in order to avoid an undesirable carbonate formation.
Polymeric phthalocyanines exhibit particularly high electrical conductivities, which may be greater by ten orders of magnitude than the conductivities of monomeric phthalocyanines.
Polymeric phthalocyanines also exhibit higher electrocatalytic activities for oxygen reduction.
However, polymeric phthalocyanines cannot be sublimated, as opposed to monomeric phthalocyanines.
The different catalytic activities of various chelate systems depend on the type of central atom among other things.
The electrocatalytic properties of phthalocyanines may be used e.g. for energy conversion in fuel cells.
The photoelectrocatalytic properties of phthalocyanines may be exploited in electrochemical solar cells.
Investigations have shown that the electrical and catalytic properties of N4-chelates may depend to a great extent on their method and conditions of preparation. The industrial manufacture of N4-chelates for use in electrodes thus requires their synthesis under carefully controlled conditions.
The production of electrodes from N4-chelates alone has not been possible until now and chelates must be generally combined with substrate materials in order to provide an electrode body of suitable shape.
It has moreover been found that the electrical and catalytic properties of chelates also depend to a great extent on the starting material used for forming the N4-chelates, as well as the substrate materials.
Proper selection of these starting materials is thus particularly critical for the production of electrodes with stable performance comprising
N4-chelates on a substrate.
Such materials must be mutually compatible and moreover suitable for processing into electrodes.
However, the selection of such organic and inorganic starting materials suitable for the manufacture of stable electrodes is generally quite difficult.
A suitable manufacturing process must moreover be found so that it can be carefully controlled to thereby ensure reproducibility.
Investigations have further shown that the chemical and physical stability of oligomeric and polymeric N4-chelates also depend to a great extent on the starting materials of the chelate, their purity, the conditions under which the chelate is produced, and more particularly the structure of the resulting chelate.
Loss of metal from the chelate, or any other degradation due to chemical or physical attack, must thus be avoided as far as possible in order to be able to ensure satisfactory stable performance of electrodes comprising chelates.
The formation of cheiate coatings on a prefabricated electrode body is particularly suitable for the production of electrodes having any desired dimensions or shape.
In that case, however, in addition to the already mentioned requirements regarding proper selection of materials, process control and chelate stability, a chelate coating must also meet the essential requirement of high adherence to the underlying electrode body providing a coating substrate.
Summary of the Invention
An object of the invention is to provide electrodes with stable semiconducting N4-chelate coatings.
Another object is to provide such N4-chelate coatings which are substantially insoluble and stable in both acid and alkaline media.
A futher object of the invention is to provide such coatings with as high adherence as possible to an electrode body providing a substrate for the coating. Another object of the invention is to provide such electrode coatings with a controlled amount of metal distributed as evenly as possible throughout the N4-chelate.
Still another object is to provide stable N4-chelate coatings with reproducible, electrical and catalytic properties.
A further object of the invention is to provide electrodes with electrocatalytic N4-chelate coatings providing stable prolonged electrochemical performance under corrosive conditions.
Still another object of the invention is to provide for the reproducible manufacture of electrodes coated with N4-chelates on an industrial scale.
The invention provides a method as set forth in the claims.
The expression metal coordination sites, as used here with reference to the invention, covers metal sites either in the metallic state, or in the form of any oxide, salt or other compound capable of providing central metal ions attached by coordinate links to the ligands of the N4-chelate network.
Investigations have shown that stable adherent
N4-chelate coatings according to the invention may be formed more particularly on valve metal substrates, such as titanium.
The film-forming properties of valve metals can provide particularly stable electrode supports and moreover provide metal coordination sites in oxide form which have been found to provide excellent coordination and bonding of the N4chelate coating to the support.
Different types of N4-chelates are described for example by H. Jahnke et al in Topics of Current
Chemistry Vol.61, 1976, P. 133-181.
The present invention provides a method of coating an electrode support body with a polymeric chelate network formed in situ on the support body and coordinated to metal sites at the surface of said body, in such a manner as to thereby provide a substantially uniform, semiconducting, insoluble chelate coating bonded via said metal sites to the surface of the support body. In accordance with the invention, said chelate coating is more particularly formed by bringing the surface of said support body into contact with a vapor phase comprising a tetranitrile compound at a predetermined elevated temperature so as to carry out heterogeneous reaction at said surface for a sufficient time to form thereon a predetermined amount of an N4-chelate per unit area of said surface.By carefully controlling the reaction conditions and limiting the duration of heterogeneous reaction, a substantially pure N4chelate film of limited thickness may thus be rapidly deposited on said support body and firmly anchored to its surface.
A relatively thin, substantially uniform film of
N4-chelate firmly adhering to the substrate body, and having metal originating from said surface distributed throughout this film, may thus be formed in situ according to the invention, in a simple reproducible deposition step of short duration, e.g. from about 30 minutes to 1 hour.
The present invention further provides for a post-treatment, under controlled conditions and for a sufficient period of time, such that the previously deposited N4-chelate may be subjected to controlled curing, to thereby undergo chemical and physical changes, especially extensive crosslinking and conversion to a substantially uniform, insoluble N4-polychelate of high molecular weight.
For this purpose, a thermal post-treatment at an elevated temperature of e.g. 3000--6000C may thus be reproducibly carried out in a subsequent step which is independent of the prior chelate deposition, and hence may be carried out independently in a different apparatus to that used for said deposition.
In order to obtain chelate coatings of any desired thickness within practical limits, the chelates may be deposited according to the invention in several successive steps wherein the chelate formed per unit area is restricted each time to a predetermined limit, so as to gradually build up a coating composed of relatively thin chelate films successively deposited.
In that case, in order to ensure sufficient metal for chelation, good coordination bonding of said films, more or less uniform metal distribution, and high electrical conductivity, additional metal may be applied to the preceding film in any suitable way or by codeposition with the tetranitrile from the vapor phase.
Thermal treatment of th N4-chelate formed in situ on the substrate may moreover be carried out subsequently under carefully controlled conditions in accordance with the invention, e.g.
at 3000 to 6000C so as to provide extensive cross-linking and conversion to a substantially stable insoluble poly-N4 chelate coating.
This controlled treatment for conversion to a polychelate coating may be readily carried out in any suitable relatively simple furnace, without applying a vacuum, i.e. the in situ synthesie of the chelate and its conversion to an insoluble polychelate may be carried out separately with different types of equipment.
The invention also provides an electrode as set forth in the claims.
The amount of chelate to be formed each time by controlled in situ synthesis according to the invention may be empirically established by preliminary experiments carried out with each type of tetranitrile compound to be used as starting material for the chelate coating and with each type of substrate to be used for this coating.
It has been experimentally established that tetracyanobenzene (TCB) may be advantageously used to produce stable polychelate coatings on metal plates in accordance with the invention.
Particularly good results were achieved when
TCB was used to produce such polychelate coatings on titanium plates. However, other valve metals such as Ta, Zr, Nb, W or Mo may also be applied to provide substrates for producing coatings according to the invention.
Other tetranitrile compounds than TCB may likewise be used as starting material for producing polychelate coatings in accordance with the invention. Thus, for example, other cyclic tetranitriles such as: tetracyanothiophene, tetracyanopyrazine, tetracyanonaphthalene tetracya nofurane, tetracyanodiphenyl, tetracyanodiphenyl ether, tetracyanopyridine tetracyanodiphenyl sulfone, or tetracyanobenzophenone, may also be used as starting materials for coating according to the invention. Tetracyanoethylene (TCNE) may also be used as a starting material for coating according to the invention.
Besides said valve metals, other metals such as
Co, Fe, Ni A2 and Cu could also be used to provide metal coordination sites on the coating substrate body, which may have any suitable shape such as e.g. a plate, grid or rod.
The electrode body used as a coating substrate may moreover be porous, at least at the substrate surface on which said heterogeneous reaction is to be carried out.
Thus, for example an electrode body with a porous carbon or zeolite structure may be provided with metal coordination sites and used as a coating substrate for carrying out the invention.
Any suitable technique may be used to apply metal coordination sites to the surface of coating substrate on which the heterogeneous chelating reaction is carried out according to the invention.
Thus, for example, a metal or metal compound may be applied to said substrate surface, either from solution of from the vapour phase.
On the other hand, when a metallic substrate surface is used to carry out the invention, it may consist of any suitable alloy which provides different chelating metals as coordination sites.
"Mixed" chelates may thus be produced according to the invention, in order to combine useful (complementary) properties of different chelating metals.
This allows given amounts of any suitable catalysts to be provided by said substrate surface and uniformly incorporated in the coating in accordance with the invention.
When a metallic substrate is used to provide coordination sites for coating according to the invention, a free metal or alloy (in the metallic state) may either entirely form the electrode body to be coated, or else may cover any suitable electrode support body, consisting preferably of an electrically conducting material such as e.g.
carbon.
Metal coordination sites may moreover be provided in the form of metal oxides or salts which may enhance bonding of the coating to the substrate.
When several reaction stages are successively carried out according to the invention, additional metal coordination sites may be applied, in metallic form or in the form of metal compounds while the coating is being gradually built up according to the invention.
Controlled amount of different types of metals may thus be incorporated more or less uniformly in the coating, and may respectively serve to provide metal coordination sites for the chelate formation, or act as conductive and/or catalytic dopants to enhance, the properties of the coating.
Thus for example compounds of platinum group metals may be incorporated in the coating as described above, and may be subsequently converted to metals or oxides by thermal treatment.
The following examples may illustrate coating conditions which may be used to carry out the invention.
Samples of sheet steel (1 %C) with a total exposed surface area 1 5 cm2 were pretreated by degreasing for 30 minutes in an ethanol-toluene mixture and mechanical polishing. Three pretreated samples to be coated were inserted into a glass reactor of about 200 cc volume, together with 45 mg of tetracyanobenzene (TCB).
After evacuating and sealing the reactor under a vacuum of about 10-3 Torr, the reactor was heated to 4000 C. This temperature was maintained for 24 hours to provide reaction and heat treatment followed by slow cooling down to room temperature.
A thin, uniform, strong chelate coating of deep purple colour was thus obtained and showed high adherence when subjected to a Scotch tape test.
Another similar sample, which was further pretreated with 20 wt% H2SO4 at 500C, was
coated in the same reactor. The amount of TCB in the reactor was 8 mg, while the reactor was
maintained at 5000C for 24 hours for reaction
and heat treatment.
The resulting chelate coating showed no sign
of deterioration after immersion for 20 minutes in 1 5% H2SO4 at 600C.
Samples of steel sheet (1% C) with a total
exposed surface area of 1 5 cm2 were pretreated
by sandblasting and degreasing for 30 min. in an.
ethanol-toluene mixture.
The pretreated samples to be coated were
inserted together with 90 mg of
tetracyanoethylene (TCNE) into a glass reactor of 200 cc volume.
The reactor was next evacuated and sealed
under a vacuum of about 10-3 Torr.
The reactor was then heated to 6000C and maintained for 24 hours at this temperature for reaction and heat treatment, followed by slow cooling to room temperature.
The resulting coating formed on the samples had a grey color and showed high adherence when subjected to a Scotch tape test. After immersion for one hour in 1 5 wt% H2SO4at 600C, the coated sample showed no trace of deterioration.
Another sample was coated under the same conditions described above, while the amount of
TCNE in the vapour phase per unit area of the sample were reduced by a factor of about four.
A chelate coating with high adherence was also obtained in this case.
A titanium sheet sample of 1 cm2 area was degreased and mechanically polished and then introduced into a glass reactor vessel (200 cc volume) containing 2 mg of tetracyanobenzene (TCB).
After evacuating and sealing the reactor under a vacuum of 10-2 Torr, the reactor was heated to 4000C and maintained at this temperature for 24 hours to carry out chelation and heat treatment, followed by cooling down to room temperature.
The resulting chelate coating exhibited good adherence to the titanium substrate.
The titanium sample with a chelate coating was then introduced into a photoelectrochemical cell containing the ferri/ferrocyanide redox couple and its photoelectrocatalytic properties were tested, showing a three times higher current under illumination than in the absence of light at a given potential.
A semiconducting N4-chelate coating formed in situ on an electrode substrate according to the invention can provide various significant advantages.
Restriction of the weight/surface ratio of the
N4-chelate formed in situ, so as to be able to provide sufficient metal coordination sites for chelate formation in all cases allows a considerable improvement of the coating properties with regard to stability, electrical conductivity, electrocatalytic activity, and bonding to the substrate.
Degradation of the chelate coating due to demetallisation, hydrolysis and/or oxidation may thus be substantially retarded. The underlying electrode body may moreover gradually provide additional metal to stabilize the chelate coating.
It has moreover been found that substantial conversion to an insoluble polymeric N4-chelate network may be ensured by providing an overstoichiometry of the metal coordination sites available for reaction with the tetranitrile. This may- be achieved by said restriction of the weight/surface ratio of the chelate formed in situ.
Controlled thermal treatment can moreover further stabilize the N4-chelate network structure to which metal ions are strongly attached by coordinate lines.
The stable N4-chelate network may serve as a protective coating against corrosion.
Such a protective coating may serve for example as a slow release barrier for metal ions coming from the electrode support body.
Claims (20)
1. A method of coating an electrode body with a chelate, characterized by:
(a) bringing a vapour phase comprising a tetranitrile compound at a predetermined elevated temperature into contact with an electrode body providing at its surface metal coordination sites for forming an N4-chelate with said compound;
(b) carrying out a controlled heterogeneous chelating reaction at elevated temperature on the electrode body while controlling the duration of said reaction so that a predetermined, limited amount of N4-chelate is formed on the electrode body per unit area of said surface and is coordinated to the metal sites of this surface;;
(c) subjecting the N4-chelate thus formed to a controlled thermal treatment for a sufficient time to convert said N4-chelate into a cross-linked N4chelate network coordinated to said metal sites and thereby anchored to said surface, to thereby form a stable, semiconducting substantially uniform polychelate coating firmly adhering to the electrode body.
2. The method according to claim 1, characterized in that said vapour phase comprises a cyclic tetranitrile compound for forming said polychelate coating.
3. The method according to claim 2, characterized in that said tetranitrile compound is tetracyanobenzene.
4. The method according to any of the preceding claims, characterized in that the electrode body comprises a valve metal or valve metal alloy providing said metal coordination sites.
5. The method according to any of the preceding claims, characterized in that said heterogeneous chelating reaction is carred out at a temperature lying between 2000C and 6000C.
6. The method according to claim 3, characterized in that said heterogeneous chelating reaction is carried out at a temperature of 3000C to 5000C.
7. The method according to claim 1, characterized in that said tetranitrile compound is tetracyanoethylene, and that said heterogeneous chelating reaction is carried out at a temperature of 4000C to 6000C.
8. The method according to any of the preceding claims, characterized in that said thermal treatment is carried out in a protective atmosphere or vacuum so as to prevent deterioration of said coating by oxidation.
9. The method according to claim 8, characterized in that said thermal treatment is carried out at a temperature lying between 3000C and 6000 C.
10. The method according to claim 9, characterized in that a further thermal treatment is carried out at a temperature lying between 6000C and 9000C in a protective atmosphere to enhance the electrocatalytic properties of said polychelate coating.
11. The method according to any of the preceding claims characterized in that said heterogeneous chelating reaction is followed by a thermal treatment carried out at a higher temperature than said reaction.
1 2. The method according to any of the preceding claims, characterized in that said heterogeneous reaction is carried out in successive stages wherein several layers each consisting of a limited amount of N4-chelate are successively formed so that a coating of desired thickness is gradually built up.
1 3. The method according to claim 12, characterized in that additional metal coordination sites are formed while said coating is being gradually built up.
14. The method according to claim 13, characterized in that said additional metal coordination sites are applied, between successive reaction stages, onto one or more of said layers.
1 5. The method according to claim 12 characterized in that said additional metal coordination sites are applied while carrying out at least some of said successive reaction stages.
1 6. The method according to any of the preceding claims, characterized in that said coordination sites are at least partly in the form of a metal oxide.
17. The method according to any of claims 12 to 15, characterized in that said reaction stages and said thermal treatment are carried out repeatedly in a cyclic manner.
1 8. An electrode comprising a semiconducting coating, characterized in that said coating comprises a stable, insoluble polymeric N4-chelate network formed in situ on an electrode support body providing metal sites whereby the chelate network is coordinated and bonded to the support body.
1 9. An electrode according to claim 18, manufactured by any one of claims 1 to 17.
20. An electrode according to claim 18 or 19, characterized in that said electrode body comprises titanium or a titanium alloy providing said metal coordination sites.
Priority Applications (18)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8006230A GB2070038A (en) | 1980-02-25 | 1980-02-25 | Method of Producing Semi- conducting N4-chelate Electrode Coating |
| CA000370266A CA1185149A (en) | 1980-02-25 | 1981-02-06 | Process for manufacturing a polychelate coating |
| JP56501048A JPS57500200A (en) | 1980-02-25 | 1981-02-23 | |
| AU69243/81A AU6924381A (en) | 1980-02-25 | 1981-02-23 | Process for manufacturing a polychelate coating |
| GR64219A GR74007B (en) | 1980-02-25 | 1981-02-23 | |
| US06/315,852 US4448803A (en) | 1980-02-25 | 1981-02-23 | Process for manufacturng a polychelate coating |
| DD81227814A DD156537A5 (en) | 1980-02-25 | 1981-02-23 | ELECTRODE AND METHOD FOR THE PRODUCTION THEREOF |
| PCT/US1981/000217 WO1981002432A1 (en) | 1980-02-25 | 1981-02-23 | Process for manufacturing a polychelate coating |
| FI813322A FI813322L (en) | 1980-02-25 | 1981-02-23 | FRAMEWORK FOR FRAMING PROCESSING |
| BR8106833A BR8106833A (en) | 1980-02-25 | 1981-02-23 | PROCESS TO PRODUCE A POLYAQUELATE COATING |
| ES499757A ES499757A0 (en) | 1980-02-25 | 1981-02-24 | A PROCEDURE FOR THE MANUFACTURE OF AN ELECTRICALLY CONDUCTIVE STABLE POLYKELATE COATING |
| ZA00811224A ZA811224B (en) | 1980-02-25 | 1981-02-24 | Process for manufacturing a polychelate coating |
| AT81300761T ATE9495T1 (en) | 1980-02-25 | 1981-02-24 | PROCESS FOR MAKING A POLYCHELATE COATING AND ELECTRODE WITH SUCH COATING. |
| EP81300761A EP0036709B1 (en) | 1980-02-25 | 1981-02-24 | Process for manufacturing a polychelate coating and electrode coated therewith |
| DE8181300761T DE3166104D1 (en) | 1980-02-25 | 1981-02-24 | Process for manufacturing a polychelate coating and electrode coated therewith |
| IL62207A IL62207A (en) | 1980-02-25 | 1981-02-24 | Manufacture of polychelate coatings and electrodes with such coatings |
| NO813592A NO813592L (en) | 1980-02-25 | 1981-10-23 | PROCEDURE FOR PREPARING A POLYCHELATE COAT |
| DK469281A DK469281A (en) | 1980-02-25 | 1981-10-23 | PROCEDURE FOR PREPARING A POLYCHELATE COVER |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8006230A GB2070038A (en) | 1980-02-25 | 1980-02-25 | Method of Producing Semi- conducting N4-chelate Electrode Coating |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB2070038A true GB2070038A (en) | 1981-09-03 |
Family
ID=10511638
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8006230A Withdrawn GB2070038A (en) | 1980-02-25 | 1980-02-25 | Method of Producing Semi- conducting N4-chelate Electrode Coating |
Country Status (4)
| Country | Link |
|---|---|
| JP (1) | JPS57500200A (en) |
| ES (1) | ES499757A0 (en) |
| GB (1) | GB2070038A (en) |
| ZA (1) | ZA811224B (en) |
-
1980
- 1980-02-25 GB GB8006230A patent/GB2070038A/en not_active Withdrawn
-
1981
- 1981-02-23 JP JP56501048A patent/JPS57500200A/ja active Pending
- 1981-02-24 ZA ZA00811224A patent/ZA811224B/en unknown
- 1981-02-24 ES ES499757A patent/ES499757A0/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| ES8204478A1 (en) | 1982-05-01 |
| ZA811224B (en) | 1982-03-31 |
| JPS57500200A (en) | 1982-02-04 |
| ES499757A0 (en) | 1982-05-01 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |