Selective visible-light-driven CO2 reduction on a p-type dye-sensitized NiO photocathode.

We present a photocathode assembly for the visible-light-driven selective reduction of CO2 to CO at potentials below the thermodynamic equilibrium in the dark. The photoelectrode comprises a porous p-type semiconducting NiO electrode modified with the visible-light-responsive organic dye P1 and the reversible CO2 cycling enzyme carbon monoxide dehydrogenase. The direct electrochemistry of the enzymatic electrocatalyst on NiO shows that in the dark the electrocatalytic behavior is rectified toward CO oxidation, with the reactivity being governed by the carrier availability at the semiconductor-catalyst interface.