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

Abstract

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.