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WO2007010313A2 - Electrode en polymere conducteur multi-composants et utilisation - Google Patents

Electrode en polymere conducteur multi-composants et utilisation Download PDF

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Publication number
WO2007010313A2
WO2007010313A2 PCT/HU2006/000060 HU2006000060W WO2007010313A2 WO 2007010313 A2 WO2007010313 A2 WO 2007010313A2 HU 2006000060 W HU2006000060 W HU 2006000060W WO 2007010313 A2 WO2007010313 A2 WO 2007010313A2
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electrode
electrode according
electron transfer
enzyme
conducting polymer
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WO2007010313A3 (fr
Inventor
Visy Csaba
Kovács KORNÉL
Peintler-Kriván EMESE
Rákhely GÁBOR
Csízi JÚLIA IVETT
Varga ANDRÁS
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University of Szeged
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University of Szeged
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    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12Q—MEASURING OR TESTING PROCESSES INVOLVING ENZYMES, NUCLEIC ACIDS OR MICROORGANISMS; COMPOSITIONS OR TEST PAPERS THEREFOR; PROCESSES OF PREPARING SUCH COMPOSITIONS; CONDITION-RESPONSIVE CONTROL IN MICROBIOLOGICAL OR ENZYMOLOGICAL PROCESSES
    • C12Q1/00—Measuring or testing processes involving enzymes, nucleic acids or microorganisms; Compositions therefor; Processes of preparing such compositions
    • C12Q1/001—Enzyme electrodes
    • C12Q1/004—Enzyme electrodes mediator-assisted
    • 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
    • C25B1/01—Products
    • C25B1/02—Hydrogen or oxygen
    • 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
    • C25B11/091—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of at least one catalytic element and at least one catalytic compound; consisting of two or more catalytic elements or catalytic compounds
    • C25B11/095—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of at least one catalytic element and at least one catalytic compound; consisting of two or more catalytic elements or catalytic compounds at least one of the compounds being organic
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2333/00—Assays involving biological materials from specific organisms or of a specific nature
    • G01N2333/90—Enzymes; Proenzymes
    • G01N2333/902—Oxidoreductases (1.)
    • G01N2333/90238—Oxidoreductases (1.) acting on hydrogen as donor (1.12)

Definitions

  • Multi-component conducting polymer electrode and use thereof are Multi-component conducting polymer electrode and use thereof
  • the subject of the invention is a multi-component conducting polymer electrode containing an electron transfer mediator, characterized by that the electron transfer mediator is an organic complex compound containing a transition metal with variable valency,
  • the electrode according to the invention is particularly suitable for the realization of redox processes at the boundary of the electrode and its surrounding medium, e.g. for the electro- biocatalytic production of hydrogen catalyzed by a hydrogenase enzyme.
  • Electrodes including conducting polymers.
  • Conducting polymers are organic macromolecules having conjugation along the polymeric chain which can be altered electrochemically to develop electronically conducting material [I]. These polymers can be formed from the solution of their monomer either chemically or electrochemically on the surface of any conducting metal (especially platinum or graphite), or any (even non-conducting) surface can be coated with them by applying appropriate procedures.
  • the conducting polymer layer formed on the surface of the conducting metal constitutes a new layer having new and different properties compared to the support, so it modifies basically the properties of the electrode.
  • the conducting polymer part of the electrode is formed in oxidized state, and their positive charges are compensated by oppositely charged ions being present during the preparation [I].
  • biologically important materials e.g. enzymes can be immobilized in them [2].
  • the incorporation of the materials can be facilitated by their anionic character. Consequently, the incorporation of ampholytic biological materials is possible only if the pH of the solution is higher than the isoelectronic point of the organic substance [3].
  • the biological buffers seem to be suitable [4] in which the mass of the anion is usually larger than 200 D (200 atomic unit).
  • PIPES disulfonic acid derivative of piperazine
  • the low rate of the polymerization and the limitations of the stable immobilization required that additional electrolytes (e.g. perchlorate, chloride and dodecyl sulfate) had to be present during the preparation of the polymer films [5]. Later this technique became generally applied, so the polymerization solutions buffered by PIPES generally contained the above- mentioned or similar additives.
  • a conducting polymer is suitable as electrode of enzymatic sensors because the organic matrix ensures a favorable environment to realize the electron transfer to the active center of oxido-reductase enzymes having complicated structure. Moreover, conducting polymers are also able to transmit the electronic signal for the detection.
  • mediators are also applied (mentioned first in [10]). The aim with these mediators is to increase the sensitivity of the electroanalytical applications.
  • the mediators used so far in sensor applications are as follows: derivatives of ferrocene (see ref.
  • the mediator molecule is the vitamin B12 [cyanocobalamin, see the Merck Index , ed. 11, p. 1577. (1989),from now on: B12]. It is known that B12 has redox activity [11-12] but this behavior was studied only at carbon and mercury electrodes. It can be applied as catalyst in redox processes, but it has been applied so far either in liquid phase [13-14] or its adsorptive ability was exploited, e.g. in the determination of NO ⁇ -ions, which were bound coordinatively by B 12 [13].
  • JP56112071 B12 is mixed with carbon powder, activated carbon, graphite or "acetylene black” powder. This mixture is spread on silver or nickel surface under high pressure.
  • the "acetylene black” is mentioned there as a possible form of the carbon electrodes beside the carbon powder, activated carbon and graphite electrodes, but it is not identical with the conducting polyacetylene [15].
  • the primary subject of the invention is a multi-component electrode, which is at least partially covered by a conducting polymer at least on that part of its surface that is in connection with the surrounding medium, and which contains an electron transfer mediator and counter ion, characterized by that the electron transfer mediator is a complex compound containing a transition metal with variable valency.
  • Any conjugated polymer can be used as conducting polymer (polypyrrole, polyaniline, polythiophene, polyacetylene, their derivatives or the copolymers built up from their monomers), where the monomers are soluble in a solvent in which the organic compound to be incorporated may exist without damage.
  • Polypyrrole was found particularly preferable.
  • the mass of the anion is preferably larger than 200 D, more preferably larger than 300 D.
  • the charge of the counter ion depends on the charge found in the skeleton of the conducting polymer.
  • the counter ion is an anion.
  • the following buffer systems deliver the appropriately sized anions: PIPES, MES (morpholino-ethane- sulfonic acid), BES [bis(hydroxyethyl) amino-ethanesulfonic acid], MOPS (morpholino- propanesulfonic acid), TES ⁇ tris[(hydroxymethyl)methyl]amino-ethane-sulfonic acid ⁇ , HEPES (hydroxyethylpyperazine-ethanesulfonic acid).
  • PIPES, MES and BES are recommended in case of polypyrrole [4], but PIPES is the most preferred.
  • organic complex compounds of transition metals with variable valency are applied as electron transfer mediator.
  • These complexes have a redox metal center, where the central metal can preferably be cobalt, iron, chromium, nickel, copper, vanadium or manganese.
  • the given valency of the ion is an unstable oxidation state.
  • the metal center of the complex is able to take part in redox processes on the basis of its variable valency, thus its oxidation number increases or decreases upon oxidation or reduction, respectively. Consequently, the central "metal atom" can also exist in ionic form in the complex compound.
  • the organic complex forming part of the complex compound applied as electron transfer mediator is preferably a nitrogen atom containing heterocyclic system having more rings, which contains delocalized electrons preferably.
  • such compounds may be applied in which the part playing important role in the complex formation has aporphyrine (e.g. hem), corrin or analogue structure.
  • Very good electron transfer mediator behavior is shown by such complexing molecules in case of which the central metal atom is coordinated with 4 to 6 nitrogen atoms, more preferably with 6 nitrogen atoms.
  • such mediator is chosen to be built into the electrode which can ensure the electrode potential appropriate for the redox process to be realized.
  • B 12 electron transfer mediator which contains cobalt atom as central metal atom with 6- fold nitrogen coordination and the cobalt is environed by partially saturated porphyrine skeleton with 5 double bonds. Beside the excellent mediator function of B 12, it can be regarded as a bio-conform substrate based on its known medical applications.
  • the electron transfer mediator can be an inorganic complex, too, containing the above- mentioned transition metal with variable valency. For example: [Co(TN(H 3 ⁇ (NC ⁇ ) ⁇ ] " ,
  • the preparation of the electrode according to the invention is realized preferably by electrochemical method, preferably at room temperature.
  • the preferred electrochemical procedure is the chronocoulometry by which the thickness of the polymer can be controlled.
  • As support electrode preferably noble metal or steel, more preferably platinum or stainless steel (SS) electrode is used, which previously was preferably cleaned and/or electrochemically pretreated [in case of Pt it is carried out at potential of -1.2-(-0.2) V, usually, with respect to Ag/ AgCl (3.4 M KCl) reference electrode; in case of stainless steel polishing is followed by bleaching in water then rinsing with acetone and carbon tetrachloride]. After the pretreatment of the surface, the potential was set to the polymerization value (which is +0.8 V with respect to the reference electrode mentioned above in case of the preferred pyrrole monomer).
  • the pH of the monomer solution was set to the appropriate value of the electron transferring mediator (if it is an ampholyte, the pH must be higher than its isoelectronic point).
  • the applied buffer must contain an anion having molecular mass preferably larger than 200 D, more preferably 300 D.
  • a preferred buffer system is the fully protonated PIPES and its disodium salt in appropriate ratio, adjusting the pH of the system between 4.5 to 8.
  • MES morpholino-ethanesulfonic acid
  • BES bis(hydroxyethyl)amino- ethanesulfonic acid
  • MOPS morpholino-propanesulfonic acid
  • TES tris[(hydroxymethyl)methyl]amino-ethanesulfonic acid ⁇
  • HEPES hydroxyethyl-pyperazine- ethanesulfonic acid
  • Salts which exert no or negligible influence on the pH of the solution can also be applied in order to increase the conductance of the solution, but they lead to the incorporation of the anions having the above-mentioned size and mass values [e.g. lauryl sulfate (also named as dodecyl sulfate) can be applied, see example 3].
  • lauryl sulfate also named as dodecyl sulfate
  • the monomer After setting pH the monomer is added to the solution in a concentration of preferably 0.01 to 1 M, more preferably 0.1 to 0.6 M, then the electron transfer mediator is added in a concentration of preferably 0.0001 to 0.1 M, more preferably 0.001 to 0.01 M.
  • the electron transfer mediator is added in a concentration of preferably 0.0001 to 0.1 M, more preferably 0.001 to 0.01 M.
  • more than one mediator can be applied, if it is advantageous to achieve the declared aim.
  • the polymerization is carried out at a charge density of preferably up to 100 to 4000 mC/cm 2 , more preferably 400 to 3000 mC/cm 2 , even more preferably 600 to 2500 mC/cm 2 .
  • the thickness of the polymer layer on the surface of the support electrode can practically be formed arbitrary within certain range (preferably from 50 nm to the ⁇ m range).
  • the incorporation of the buffer anions, too, besides the electron transfer mediator is unavoidable during the above procedure.
  • the anions of the applied buffer do not play role in the electron transport catalyzed by the polymer electrode, but the application of the buffer ensures the effective incorporation of the mediator which preserves its electrochemical activity in polymer having the above additives.
  • the conductive polymer layer prepared in Example 1 still contains PIPES anions besides polypyrrole and B 12 main components, and in Example 3 lauryl sulfate anions are in the conductive polymer layer, too.
  • the multi-component electrode according to the invention can be applied in several fields since the electrode assists the electron transfer to be significantly easier (i.e. through a lower energy barrier), consequently faster between the electrode and one or more components (in the following parts: component) of the surrounding medium (preferably a buffered solution).
  • component in the following parts: component
  • the second object of the invention is the use of the above-detailed conducting polymer based electrode for realizing redox processes occurring at the boundary of the electrode and its surrounding medium.
  • the special electron transfer mediator applied in the electrode according to the invention can be used for processes when the electrode transfers the electron to the species in the medium (e.g. regeneration of co-enzymes, dehalogenization) and also for processes when the electron transfer occurs in the reversed direction (oxidation of thiols, cistein, etc.).
  • the electrode according to the invention is applicable during any electrochemical measurement (even involving an enzyme reaction) if the component to be determined in the solution (which can be a small or a large molecule, e.g. protein with complicated structure or enzyme) is able to become either oxidized or reduced . Therefore, the electrode according to the invention is applicable either in reductive processes (reduction of C ⁇ , NO ⁇ " , NC ⁇ " , CO2 etc.) or in oxidative processes (e.g. special substances required by the physiological blood- analysis).
  • bio-compatible electrode in cases of biological measurements, especially in vivo (e.g. diagnostics or monitoring).
  • Such electrode includes bio-compatible mediator, like B 12.
  • the electrodes in the invention can be applied excellently for electrochemical transformations when the aim is the production of a gas, especially oxygen or hydrogen [18].
  • a gas especially oxygen or hydrogen [18].
  • a structurally complicated organic entity molecule
  • the gas production which can be a bio- catalyst, preferably an enzyme [19].
  • the electrolysis can be carried out by any stationary procedure (e.g. potentiostatic or galvanostatic one) through either periodical or continuous ways.
  • the cathodic process is the important one, the necessary electrons can originate from any anodic process acting as the electron source (e.g. KI/In system, oxidation of water, oxidation with laccase enzyme or enzymatic oxidation of glucose).
  • any cathodic process can be applied which ensures the consumption of electrons (e.g., H reduction, Fe(III) reduction [20], reduction of coenzymes).
  • the most emphasized application area of the electrode according to the invention is its use to produce hydrogen gas, since it is regarded as an important energy source all over the world.
  • the production of hydrogen is possible from water or organic materials (e.g. natural gas) by using external, primary energy source. But hydrogen can already be produced from renewable primary energy sources with reasonable efficiency, too.
  • the fast evolution of biotechnological devices and systems is making more and more realistic the extensive application of hydrogen.
  • a main type of hydrogen production is based on direct biological splitting of water, e.g., by algae.
  • the solar energy reaching the Earth's surface is tried to apply directly for energy production.
  • this approach would require the construction of huge bioreactors.
  • the hydrogen production step is extremely oxygen sensitive in algae. Consequently, any system based on biological splitting of water workable in practice, too, primarily needs an oxygen resistant hydrogenase. Up to now no hydrogenase has been found with oxygen resistant feature in microorganisms capable of splitting of water [22].
  • biohydrogen production is embodied by systems based on indirect splitting of water.
  • ,Indirect means that the steps of the process are separated in space or in time.
  • chemical energy is produced with the help of photosynthesis and bound in a biomass and later this biomass is converted into H 2 .
  • the fermentation processes provide another type of implementation.
  • Some microbes possess the capability to obtain the energy for growth from fermentative transformation of organic substances. Fermentation is not the most efficient process energetically, but it is a reliable form of metabolism where the cells get rid of their excess energy relatively easily in the form of hydrogen gas [23].
  • Hydrogenases can be found primarily in bacteria and algae. Since the hydrogenase catalyzes oxidation-reduction processes, this enzyme is in connection with the processes of the electron transport chain of bacteria, acting either as an electron donor or an electron acceptor. The simple looking task is solved by the enzyme through a complex molecular mechanism. Most of the known hydrogenases are redox metalloenzymes containing Ni or Fe atoms. In living cells the specific and complex protein molecule, surrounding the metals, and the interaction between the protein and the metal atoms make capable the Ni and Fe atoms buried in the molecule to catalyze the elementary steps of either the hydrogen synthesis or hydrogen decomposition.
  • Hydrogenases are spread widely in the Nature, for example the most thoroughly studied bacterium, the Escherichia coli can synthetize, depending on the growth conditions, 4 NiFe hydrogenases having different functions. In order to utilize enzymes in biotechnological applications they have to be stable enough. Similarly to most of the redox metalloenzymes, the majority of hydrogenases looses their activity easily when they are exposed to atmospheric oxygen or high temperature. This is due to the sensitive interaction between the metal atoms and the surrounding protein. Nevertheless exceptions exist, since a few microorganisms are known to contain hydrogenase with outstanding stability properties. An example is the photosynthetizing sulfur-dependent purple bacterium Thiocapsa roseopersicina. One of its native enzymes is stable against proteolytic digesting, moreover, this hydrogenase is thermophilic having an optimal working temperature beyond 70 0 C. This hydrogenase is hardly sensitive to oxygen inactivation [24].
  • h ⁇ pSL An other gene family, called h ⁇ pSL, has been found in the same bacterium, which shows a high degree homology with genes of other NiFe hydrogenases.
  • the hupSL protein is labile and impractical enzyme like most of the other NiFe hydrogenases known from the literature.
  • the hynSL genes were identified as another type encoding a stable hydrogenase, which appears particularly suitable for biotechnological applications.
  • HoxYH also containing a NiFe metals in its active centre, has been discovered in T. roseopersicina, but it is dissolved in the cytoplasma.
  • Hox hydrogenase is especially interesting because, unlike the stable (Hyn) and unstable (Hup) membrane-associated hydrogenases (which are primarily responsible for the H 2 uptake and decomposition in living cells), Hox is able to produce in vivo a remarkable amount of hydrogen.
  • genes encoding a fourth hydrogenase QnipUV genes have been identified in T. roseopersicina, containing structural elements similar to H 2 -sensing, so-called sensor hydrogenase enzymes which are known from other bacteria. It means that T. roseopersicina, on the one hand, is rich in hydrogenases like e.g. E. coli and, on the other hand, is non-pathogenic and photosynthetic organism, so T. roseopersicina can be applied advantageously in biological hydrogen- producing systems [25],
  • the HynSL protein is a membrane- bound NiFe hydrogenase, which consists of a large (64 kDa) subunit (HynL) and a small (34 kDa) subunit (HynS).
  • the small subunit contains 3 F4S4 cubane structures that serve as an electron channel between the outer surface of the protein and the active NiFe center buried inside the protein.
  • the large subunit contains the NiFe heterobinuclear center playing a key role in the catalysis.
  • This hydrogenase carries most of the cellular hydrogenase activity, both in H 2 uptake and decomposition, moreover, it is thermostable and resistant to proteolytic digestion.
  • Hyn hydrogenase may vary in a wide range, between 100 and 1000 micromol H 2 /hr/mg protein depending on the conditions used in the measurement, determined by standard activity measurement methods carried out in solution. It is to be emphasized that excellent hydrogen production results were achieved in that embodiment of the present invention where polypirrole was applied as conducting polymer, vitamin B 12 was applied as electron transfer mediator and HynSL type hydrogenase of T. roseopersicina was applied as enzyme. This preferred embodiment is disclosed more precisely in Examples 2 and 4, using the electrode of Example 1 and 3, respectively, as cathode.
  • bioelectrochemical water splitting reaction can be implemented by the combination of two multi-component electrodes.
  • the B 12 When used in a fuel cell type application, the B 12 behaves as a catalyst on the oxygen electrode. Oxygen is being reduced on this electrode while under properly selected conditions the hydrogenase may work in the hydrogen consumption direction and thus current can be generated in the fuel cell.
  • the excellent electron transferring properties of the electrodes according to the invention is in connection with an efficient interaction between the surface of the electrode according to the invention and the components of the solution which take part in the electron transferring process.
  • those electrodes mean a specific sub-class of the electrodes according to invention where the surface of the electrode is covered, at least partially, with one or more material(s) which take part in the electron transfer process.
  • the one or more material(s) participating in the electron transfer process is deposited onto the electrode surface from the liquid phase contacting with the electrode.
  • the one or more materials participating in the electron transfer process can be any material having the properties discussed in the description, preferably a biocatalyst, most preferably an enzyme.
  • Fig. 1 shows the cyclic voltammetric curves of the electrode containing no mediator (PPy/PIPES) and the platinum based composite electrode, prepared according to Example 1.
  • Curve (1) shows the current values on a PPy/PIPES electrode measured at decreasing and curve (V) at increasing potential scans.
  • Curve (2) shows the current values on PPy/PIPES/B12 electrode measured at decreasing and curve (2') at increasing potential values.
  • the amount of the produced hydrogen, using the electrode of example 1 is presented as a function of the applied potential (but using the opposite sign) during the electrolysis according to procedure detailed in example 2.
  • the applicability of the electrode in the invention is shown by the curve with rapidly increasing slope. Further details can be found in the evaluation part following example 2.
  • Figures 3a - 3c show the comparative curves of voltammetric behavior obtained with electrodes formed on stainless steel, with and without B 12. The differences at different scan rates in the various cases are the consequences of whether there has been a pretreatment or not, where the pretreatment is applied in order to oxidize the metallic center of B12 incorporated in the layer. The comparison of the figures shows that the pretreatment causes a reduction current surplus at the electrodes prepared with B 12. Further details can be found in the evaluation part after example 4.
  • Curves 3 and 4 in Figure 4 show the applicability of the electrode according to example 3 for hydrogen production. Curves 1 and 2 serve for comparison. Each curve in the figure shows the formation rate of hydrogen during electrolysis carried out under electrochemically identical circumstances in the following cases: 1: S S/PPy electrode only 2: SS/PPy/B12 electrode
  • Example 1 Preparation of the polypyrrole/PIPES based electrode with B12 electron transfer mediator (PPy/PIPES/B12 electrode)
  • the Pt electrode is cleaned in the mixture of hydrogen peroxide and sulfuric acid (piranha solution) and it is rinsed with water.
  • the electrode surface is pretreated electrochemically in the polymerization solution for 1 s at -0.7 V with respect to Ag/ AgCl (3.4 M KCl) reference electrode.
  • the potential of the reference electrode is +0.2 V with respect to the standard hydrogen electrode (SHE), the potential values given here are referred to the Ag/ AgCl electrode.
  • SHE standard hydrogen electrode
  • the potential values given here are referred to the Ag/ AgCl electrode.
  • Pyrrole (as monomer) is added first to the polymerization solution up to 0.5 M concentration, followed by the addition of B 12 (as electron transfer mediator, Supelco) up to 0.003 M concentration.
  • B 12 as electron transfer mediator, Supelco
  • the polymerization made up to charge density of 600 mC/cm ⁇ results in an approximately 100 nm thick polymer layer on the surface of the support electrode.
  • Example 2 Application of the electrode according to example 1 for electro- biotechnological production of hydrogen
  • the electrode is placed into a three electrodes containing electrolysis cell which has closed airspace where the counter electrode is a Pt electrode of a surface area of approx. 5 cm 2 . After placing the counter and reference electrodes in the cell, it is deoxygenized by bubbling of high-purity nitrogen gas.
  • the cell is filled with PIPES solution where the pH of the solution should be adjusted to optimal value for keeping the hydrogenase enzyme in active form [27]. In the present case, this value is 6.87, practically the neutral pH.
  • Hydrogenase enzyme kept in PIPES solution is added to the working compartment of the cell.
  • the activity ⁇ of the enzyme in the cell is 1x10 mol/min.
  • An easily oxidizable species preferably KI is added in large excess (1.5 M) into the counter electrode part of the cell in order to ensure the counter oxidation process which runs at less positive potential than the oxygen evolution.
  • the electrolysis is carried out at room temperature, preferably potentiostatically in a potential range between -0.68 and -0,74 V which equals to -0.48 and-0.54 V in SHE scale.
  • the process is carried out in sequential steps, by restarting the electrolysis again and again.
  • the amount of the evolved hydrogen gas is measured by GC (gas chromatograph) using heat conductivity detector and column filled with 5 A molecule sieves (Aldrich).
  • Figure 1 presents cyclic voltammetric curves registered at the electrodes prepared according to Example 1, in the absence of the mediator (PPy/PIPES) and in its presence (PPy/PIPES/B12).
  • Curve (1) shows the current values on PPy/PIPES electrode measured at decreasing and curve (I 1 ) at increasing potential.
  • Curve (2) shows the current values on PPy/PIPES/B12 electrode measured at decreasing and curve (2 1 ) at increasing potential. The voltammograms were performed in PIPES solutions.
  • the curves prove the incorporation of the mediator since a surplus reduction current can be seen in the negative potential range originating from the mediator being in the conductive layer of the PPy/PIPES/B12 electrode.
  • the oxidation of the mediator gives a surplus oxidation current in the positive potential range. This oxidation is realized at +0.2 V.
  • Example 3 Making PPy/B12 electrode on stainless steel (SS/PPy/B12)
  • the steel electrode must be polished then rinsed with water, acetone and carbon tetrachloride. After it the polymerization is carried out by applying a chronocoulometric procedure at a potential of +0.8 V.
  • the polymerization has been carried out in 10 ml buffer solution, which contains 0.033 M PIPES-acid, 0.1 M PIPES disodium salt and 0.15 M sodium lauryl sulfate.
  • pyrrole is added up to 0.5 M and B12 is added up to 0.003 M.
  • the polymerization made up to charge density of 2500 mClcvcr results in an approximately 400 nm thick polymer layer on the surface of the support electrode.
  • Example 4 The application of the electrode according to Example 3 for reduction process (e.g. electro-biotechnological hydrogen gas production)
  • the electrode is placed into a three electrodes containing electrolysis cell which has closed airspace where the parts of it are separated by Nafion 117 membrane.
  • the counter electrode is a two times larger Pt electrode (approx. 5 cm ) than the working electrode of Example 3.
  • PIPES solution After placing the counter and reference electrodes in the cell, it is filled with PIPES solution and deoxygenized by bubbling nitrogen gas.
  • the pH of the solution should be adjusted to optimal value for keeping the hydrogenase enzyme in active form [27]. In the present case, this value is 6.87, practically the neutral pH.
  • Hydrogenase enzyme kept in PIPES solution is added to the working compartment of the cell.
  • the activity of the enzyme in ⁇ the cell is 4.5x10 mol/min.
  • the electrolysis is carried out at room temperature, preferably potentiostatically at - 0.75 V (which equals to -0.55 V in SHE scale).
  • the overall electrolysis is carried out in sequential steps, by restarting the electrolysis again and again .
  • the amount of the evolved hydrogen gas is measured by GC (gas chromatograph) using heat conductivity detector and column filled with 5 A molecule sieves (Aldrich).
  • Figure 3a compares the voltammetric curves at a sweep rate of 10 mV/s. The first two curves run together indicating that there is no difference in currents at the electrodes in presence and absence of B12 when no pretreatment is applied. In case of a 6 s long pretreatment at +0.2 V, however, there is a significant current surplus at the electrode incorporating B 12.
  • Figures 3b and 3c present the voltammetric curves at sweep rates of 25 and 50 mV/s, respectively.
  • a significant current surplus can be measured at the electrodes containing B 12, provided a 6 s long pretreatment was applied at +0.2 V before the measurements.
  • the reason of the reduction current surplus can be explained as the polarization at +0.2 V results in the oxidation of the metallic center of B12, thus the subsequent reduction involves an extra current, too.
  • B 12 is not in oxidized stage in the layer, thus reduction surplus current cannot be measured. If B12 is not built into the layer, the pretreatment does not result in surplus current.
  • Curves 3 and 4 in Figure 4 show the rates of electro-biotechnological hydrogen gas production at the SS/PPy/B12 electrode according to Example 3 in comparison with some other cases (curves 1 and 2): 1 : S S/PPy electrode only
  • Figure 4 shows that the rate of the hydrogen production during the studied section of the electrolysis (approx. the first 6 hours) slightly decreases in the given cases, then it becomes closely steady.
  • the value of the rates at the SS/PPy/B12 electrodes compared to the case 1 is 2-3 -fold larger under otherwise identical circumstances. Besides, a significant difference has been experienced when the current efficiencies are compared. In case of electrochemical hydrogen production this value is only 0.47 - 0.53 during the electrolysis at electrode 1, it changes between 0.59 - 0.74 at electrodes 2 and 3, while values between 0.87 - 1.04 are obtained at electrode 4.

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  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Zoology (AREA)
  • Wood Science & Technology (AREA)
  • Proteomics, Peptides & Aminoacids (AREA)
  • Immunology (AREA)
  • Biochemistry (AREA)
  • Biophysics (AREA)
  • Microbiology (AREA)
  • Molecular Biology (AREA)
  • Analytical Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Biotechnology (AREA)
  • Bioinformatics & Cheminformatics (AREA)
  • General Engineering & Computer Science (AREA)
  • General Health & Medical Sciences (AREA)
  • Genetics & Genomics (AREA)
  • Inorganic Chemistry (AREA)
  • Inert Electrodes (AREA)
  • Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
  • Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)

Abstract

Electrode multi-composants au moins en partie recouverte de polymère conducteur au moins sur une partie de sa surface en liaison avec le milieu qui l'entoure, contenant un médiateur de transfert d'électron et un contre-ion. Le médiateur est un composé complexe qui contient un métal de transition à valence variable. Egalement, utilisation de l'électrode en question pour les opérations d'oxydo-réduction à la limite de l'électrode et du milieu qui l'entoure. De préférence, cette utilisation est liée à une opération d'oxydo-réduction catalysée par enzyme oxydo-réductase, de préférence pour la production d'hydrogène.
PCT/HU2006/000060 2005-07-20 2006-07-20 Electrode en polymere conducteur multi-composants et utilisation Ceased WO2007010313A2 (fr)

Applications Claiming Priority (2)

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HU0500701A HUP0500701A2 (en) 2005-07-20 2005-07-20 Conductive-polymer electrode from multicomponent system and the use thereof
HUP0500701 2005-07-20

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WO2007010313A2 true WO2007010313A2 (fr) 2007-01-25
WO2007010313A3 WO2007010313A3 (fr) 2007-05-18

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WO2007105810A1 (fr) * 2006-03-09 2007-09-20 Toyota Jidosha Kabushiki Kaisha Procédé de préparation de matériau catalytique
US7709113B2 (en) 2004-07-14 2010-05-04 The Penn State Research Foundation Bio-electrochemically assisted microbial reactor that generates hydrogen gas and methods of generating hydrogen gas
US7922878B2 (en) 2004-07-14 2011-04-12 The Penn State Research Foundation Electrohydrogenic reactor for hydrogen gas production
US8277984B2 (en) 2006-05-02 2012-10-02 The Penn State Research Foundation Substrate-enhanced microbial fuel cells
CN103316706A (zh) * 2013-06-15 2013-09-25 湖南科技大学 一种掺杂金属的聚苯胺与聚吡咯复合物碳化电催化剂及其制备方法
WO2013187982A1 (fr) * 2012-06-11 2013-12-19 Viceroy Chemical Procédé et appareil pour un catalyseur photocatalytique et électrocatalytique
US8962165B2 (en) 2006-05-02 2015-02-24 The Penn State Research Foundation Materials and configurations for scalable microbial fuel cells
US9546426B2 (en) 2013-03-07 2017-01-17 The Penn State Research Foundation Methods for hydrogen gas production
US10978713B2 (en) 2004-07-14 2021-04-13 The Penn State Research Foundation Cathodes for microbial electrolysis cells and microbial fuel cells
US20210147990A1 (en) * 2018-04-12 2021-05-20 Alliance For Sustainable Energy, Llc In vitro production of hydrogen utilizing hydrogenase

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JPS5948511B2 (ja) * 1980-02-07 1984-11-27 日本電信電話株式会社 燃料電池及び空気電池用電極
US7638228B2 (en) * 2002-11-27 2009-12-29 Saint Louis University Enzyme immobilization for use in biofuel cells and sensors

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7709113B2 (en) 2004-07-14 2010-05-04 The Penn State Research Foundation Bio-electrochemically assisted microbial reactor that generates hydrogen gas and methods of generating hydrogen gas
US7922878B2 (en) 2004-07-14 2011-04-12 The Penn State Research Foundation Electrohydrogenic reactor for hydrogen gas production
US10978713B2 (en) 2004-07-14 2021-04-13 The Penn State Research Foundation Cathodes for microbial electrolysis cells and microbial fuel cells
WO2007105810A1 (fr) * 2006-03-09 2007-09-20 Toyota Jidosha Kabushiki Kaisha Procédé de préparation de matériau catalytique
US8277984B2 (en) 2006-05-02 2012-10-02 The Penn State Research Foundation Substrate-enhanced microbial fuel cells
US8962165B2 (en) 2006-05-02 2015-02-24 The Penn State Research Foundation Materials and configurations for scalable microbial fuel cells
WO2013187982A1 (fr) * 2012-06-11 2013-12-19 Viceroy Chemical Procédé et appareil pour un catalyseur photocatalytique et électrocatalytique
US9546426B2 (en) 2013-03-07 2017-01-17 The Penn State Research Foundation Methods for hydrogen gas production
CN103316706A (zh) * 2013-06-15 2013-09-25 湖南科技大学 一种掺杂金属的聚苯胺与聚吡咯复合物碳化电催化剂及其制备方法
CN103316706B (zh) * 2013-06-15 2015-03-11 湖南科技大学 一种掺杂金属的聚苯胺与聚吡咯复合物碳化电催化剂及其制备方法
US20210147990A1 (en) * 2018-04-12 2021-05-20 Alliance For Sustainable Energy, Llc In vitro production of hydrogen utilizing hydrogenase

Also Published As

Publication number Publication date
WO2007010313A3 (fr) 2007-05-18
HU0500701D0 (en) 2005-09-28
HUP0500701A2 (en) 2007-02-28

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