Hydrogenases are enzymes that can catalyze the production of hydrogen from water and electricity and the reverse reaction of converting hydrogen to electricity. For this, it is necessary to fix them on electrodes to ensure the flow of current.
Scientists from the Laboratory of Bioenergetics and Protein Engineering (CNRS / Aix-Marseille University) and the Technical University of Munich have just developed a new specific polymer that allows the enzyme to be grafted onto the electrode while retaining its properties. catalytic for both directions of the reaction, without loss of electrical energy. Could hydrogenases soon replace the platinum currently used to produce even greener hydrogen ?
Fuel cells that convert hydrogen into electricity , or electrolysers capable of producing hydrogen by dissociating water with the help of electricity, use platinum, a rare and expensive metal , which acts as a catalyst . Enzymes called “hydrogenases” also catalyze these two reactions very quickly and with almost no loss of energy, but use non-noble metals. Hence the idea of scientists from the Laboratory of Bioenergetics and Protein Engineering (CNRS / Aix-Marseille University) and the UniversityMunich technique of connecting these hydrogenases to electrodes by incorporating them into “redox polymers” which allow the circulation of electrons and the electrical connection between the enzyme and the electrode. Usual drawback of this type of device: the redox polymer offers resistance to the flow of electrons, which makes the system inefficient from an energy point of view .
By adjusting the properties of these polymers, the scientists showed that the system could perfectly catalyze the reaction in both directions, without wasting energy.
Scientists have thus produced a fuel cell where oxygen is reduced by the bacteria bilirubin oxidase enzyme.Myrothecium verrucaria , while the hydrogenase from the bacterium Desulfovibrio desulfuricans incorporated into the polymer film oxide the hydrogen . The system can also operate efficiently in the opposite direction, for the production of H 2 by electrolysis of water.
Research is now aimed at increasing the stability of the incorporated hydrogenases so that they can withstand higher current densities and seriously compete with systems currently employing platinum-based catalysts. Results that could be useful for the implementation of other fragile catalysts such as CO-reducing enzymes2 to produce liquid fuels or value-added chemicals from renewable resources. These results are published in the journal Nature Catalysis .
Steffen Hardt, Stefanie Stapf, Dawit T. Filmon, James A. Birrell, Olaf Rüdiger, Vincent Fourmond, Christophe Léger & Nicolas Plumeré
Reversible H 2 oxidation and evolution by hydrogenase embedded in a redox polymer film
Nature Catalysis 4, 251-258 (2021)