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Variants of the highly active [NiFeSe] hydrogenase from D. vulgaris Hildenborough that exhibit enhanced O 2 tolerance were used as H 2 -oxidation catalysts in H 2 /O 2 biofuel cells. Two [NiFeSe] variants were electrically wired by means of low-potential viologen-modified redox polymers and evaluated with respect to H 2 -oxidation and stability against O 2 in the immobilized state. The two variants showed maximum current densities of (450±84) μA cm -2 for G491A and (476±172) μA cm -2 for variant G941S on glassy carbon electrodes and a higher O 2 tolerance than the wild type. In addition, the polymer protected the enzyme from O 2 damage and high-potential inactivation, establishing a triple protection for the bioanode. The use of gas-diffusion bioanodes provided current densities for H 2 -oxidation of up to 6.3 mA cm -2 . Combination of the gas-diffusion bioanode with a bilirubin oxidase-based gas-diffusion O 2 -reducing biocathode in a membrane-free biofuel cell under anode-limiting conditions showed unprecedented benchmark power densities of 4.4 mW cm -2 at 0.7 V and an open-circuit voltage of 1.14 V even at moderate catalyst loadings, outperforming the previously reported system obtained with the [NiFeSe] wild type and the [NiFe] hydrogenase from D. vulgaris Miyazaki F., (© 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

Carbon-based monoliths have been designed using a simple synthetic pathway based on using high internal phase emulsion (HIPE) as a soft template to confine the polymerization and hydrothermal carbonization of saccharide derivatives (furfural) and phenolic compounds (phloroglucinol). Monosaccharides can be isolated from the cellulosic fraction of lignocellulosic biomass and phloroglucinol can be extracted from the bark of fruit trees; however, this approach constitutes an interesting sustainable synthetic route. The macroscopic characteristics can be easily modulated; a high macroporosity and total pore volume of up to 98 % and 18 cm(3)g(-1) have been obtained, respectively. After further thermal treatment under inert atmosphere, the as-synthesized macroporous carbonized HIPEs (carbo-HIPEs) have shaping capabilities relating to interesting mechanical properties as well as a high electrical conductivity of up to 300 Sm(-1) . These conductive foams exhibit a hierarchical structure associated with the presence of both meso- and micropores that exhibit specific Brunauer-Emmett-Teller (BET) surface areas and DFT total pore volumes up to 730 m(2)g(-1) and 0.313 cm(3)g(-1) , respectively. Because of their attractive structural characteristics and intrinsic properties, these macroporous monoliths have been incorporated as a proof of principle within electrochemical devices as modified thin carbon disc electrodes. A promising two-fold improvement in the catalytic current is observed for the electrooxidation of glucose after the immobilization of a glucose oxidase-based biocatalytic mixture onto the carbo-HIPE electrodes compared to that observed if using commercial glassy carbon electrodes., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)