Über die Leerlaufspannung von Biobrennstoffzellen: Nernstverschiebung bei pseudokapazitiven Elektroden

Organic Photovoltaic Catalyst with σ-π Anchor for High-Performance Solar Hydrogen Evolution

Efficient in situ deposition of metallic cocatalyst, like zero-valent platinum (Pt), on organic photovoltaic catalysts (OPCs) is the prerequisite for their high catalytic activities. Here we develop the OPC (Y6CO), by introducing carbonyl in the core, which is available to σ-π coordinate with transition metals, due to the high-energy empty π* orbital of carbonyl. Y6CO exhibits a stronger capability to anchor Pt species and reduce them to metallic state, resulting in more Pt⁰ deposition, relative to the control OPC without the central σ-π anchor. Single-component and heterojunction nanoparticles (NPs) employing Y6CO show enhanced average hydrogen evolution rates of 230.98 and 323.22 mmol h^-1  g_[OPC] ^-1 , respectively, under AM 1.5G, 100 mW cm^-2 for 10 h, and heterojunction NPs yield the external quantum efficiencies of ca. 10 % in 500-800 nm. This work demonstrates that σ-π anchoring is one efficient strategy for integrating metallic cocatalyst and OPC for high-performance photocatalysis.

On the Mediated Electron Transfer of Immobilized Galactose Oxidase for Biotechnological Applications

The use of enzymes as catalysts in chemical synthesis offers advantages in terms of clean and highly selective transformations. Galactose oxidase (GalOx) is a remarkable enzyme with several applications in industrial conversions as it catalyzes the oxidation of primary alcohols. We have investigated the wiring of GalOx with a redox polymer; this enables mediated electron transfer with the electrode surface for its potential application in biotechnological conversions. As a result of electrochemical regeneration of the catalytic center, the formation of harmful H2 O2 is minimized during enzymatic catalysis. The introduced bioelectrode was applied to the conversion of bio-renewable platform materials, with glycerol as model substrate. The biocatalytic transformations of glycerol and 5-hydroxymethylfurfural (HMF) were investigated in a circular flow-through setup to assess the possibility of substrate over-oxidation, which is observed for glycerol oxidation but not during HMF conversion.

Redox-Polymer-Based High-Current-Density Gas-Diffusion H2 -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 H2 /O2 biofuel cell equipped with a [FeFe] hydrogenase/redox polymer-based high-current-density H2 -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 % O2 .

Redox-Polymer-Wired [NiFeSe] Hydrogenase Variants with Enhanced O2 Stability for Triple-Protected High-Current-Density H2 -Oxidation Bioanodes

Variants of the highly active [NiFeSe] hydrogenase from D. vulgaris Hildenborough that exhibit enhanced O2 tolerance were used as H2 -oxidation catalysts in H2 /O2 biofuel cells. Two [NiFeSe] variants were electrically wired by means of low-potential viologen-modified redox polymers and evaluated with respect to H2 -oxidation and stability against O2 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 O2 tolerance than the wild type. In addition, the polymer protected the enzyme from O2 damage and high-potential inactivation, establishing a triple protection for the bioanode. The use of gas-diffusion bioanodes provided current densities for H2 -oxidation of up to 6.3 mA cm-2 . Combination of the gas-diffusion bioanode with a bilirubin oxidase-based gas-diffusion O2 -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.