Scheme 1.

Schematic representation of the H₂-driven particle system for NADH-dependent biocatalysis. Oxidation of H₂ by a hydrogenase (green) transfers electrons (e⁻) into an electronically conducting particle and these are then used by an NAD⁺ reductase (blue) for selective NAD⁺ reduction. A co-immobilised NADH-dependent AHD (red) is supplied with NADH that is used for catalytic reduction of a ketone (here, acetophenone). Both hydrogen atoms of H₂ are incorporated into the product (here phenylethanol) to allow a 100 % atom-efficient chemical synthesis.