Redox‐Polymer‐Based High‐Current‐Density Gas‐Diffusion H 2 ‐Oxidation Bioanode Using [FeFe] Hydrogenase from Desulfovibrio desulfuricans in a Membrane‐free Biofuel Cell

The incorporation of highly active but also highly sensitive catalysts (e.g. the [FeFe] hydrogenase from Desulfovibrio desulfuricans) in biofuel cells is still one of the major challenges in sustainable energy conversion. We report the fabrication of a dual‐gas diffusion electrode H 2 /O 2 biofuel cell equipped with a [FeFe] hydrogenase/redox polymer‐based high‐current‐density H 2 ‐oxidation bioanode. The bioanodes show benchmark current densities of around 14 mA cm −2 and the corresponding fuel cell tests exhibit a benchmark for a hydrogenase/redox polymer‐based biofuel cell with outstanding power densities of 5.4 mW cm −2 at 0.7 V cell voltage. Furthermore, the highly sensitive [FeFe] hydrogenase is protected against oxygen damage by the redox polymer and can function under 5 % O 2 .