Enhancing the catalytic current response of H2 oxidation gas diffusion bioelectrodes using an optimized viologen‐based redox polymer and [NiFe] hydrogenase

• Published in: Electrochemical science advances Vol. 2; no. 4
• Main Authors: Lielpetere, Anna, Becker, Jana M., Szczesny, Julian, Conzuelo, Felipe, Ruff, Adrian, Birrell, James, Lubitz, Wolfgang, Schuhmann, Wolfgang
• Format: Journal Article
• Language: English
• Published: Aachen John Wiley & Sons, Inc 01-08-2022
• Subjects: bioanode; Biocatalysts; Biodiesel fuels; Biofuels; Design; Electrodes; Electrolytes; Electrons; Enzymes; gas diffusion electrode; Hydrogels; hydrogen oxidation; hydrogenase; Optimization; Oxidation; Polymer films; Polymers; redox polymer
• ISSN: 2698-5977; 2698-5977
• DOI: 10.1002/elsa.202100100

Using viologen‐based redox polymers to wire a variety of different hydrogenases to electrodes and gas diffusion electrodes is the basis to mitigate high potential deactivation of the enzyme, deactivation by molecular O2, as well as for high‐current density H2 oxidation bioanodes. To overcome electron transfer limitations by electron hopping within the viologen‐modified polymer film, a new redox polymer was designed with the highest possible viologen content together with monomers bearing crosslinking units. In combination with an immobilization sequence consisting of oxidative grafting of amino functions, covalent attachment of polymer units to these functionalities, and crosslinking of the polymer layers, an unprecedently fast electron transfer became possible. This enabled a very high current density normalized by the amount of the [NiFe] hydrogenase embedded within a viologen polymer on gas diffusion electrodes.
The design of a high‐viologen loading redox polymer coP(N3MA85‐GMA15)‐vio together with an all‐covalent immobilization strategy consisting of electro‐grafting, covalent binding of an adhesion layer, and covalent crosslinking with the polymer layer containing the entrapped hydrogenase leads to improved electron transfer rates which in return allow for high H2 oxidation currents.