Immobilized Enzymes on Graphene as Nano-Bio-Catalyst.

Using enzymes as bio-electrocatalysts is an important step toward the next level of bio-technology for energy production. In such biocatalysts, a sacrificial cofactor as an electron and proton source is needed. This is of great obstacle for upscaling, due to cofactor instability and product separation issues, which increase the costs. Here, we report a cofactor-free electroreduction of CO to a high energy density chemical (methanol) catalyzed by enzyme-graphene hybrids. The bio-catalyst consists of dehydrogenases covalently bound on a well-defined carboxyl graphene derivative, serving the role of a conductive nano-platform. This nano-bio-catalyst achieves reduction of CO to methanol at high current densities, which remain unchanged for at least 20 h of operation, without production of other soluble by-products. It is thus shown that critical improvements on stability and rate of methanol production at a high Faradaic efficiency of 12% are possible, due to the effective electrochemical process from the electrode to the enzymes the graphene platform.