Electrocatalytic and Solar‐Driven CO2 Reduction to CO with a Molecular Manganese Catalyst Immobilized on Mesoporous TiO2

Electrocatalytic CO2 reduction to CO was achieved with a novel Mn complex, fac‐[MnBr(4,4′‐bis(phosphonic acid)‐2,2′‐bipyridine)(CO)3] (MnP), immobilized on a mesoporous TiO2 electrode. A benchmark turnover number of 112±17 was attained with these TiO2|MnP electrodes after 2 h electrolysis. Post‐catalysis IR spectroscopy demonstrated that the molecular structure of the MnP catalyst was retained. UV/vis spectroscopy confirmed that an active Mn–Mn dimer was formed during catalysis on the TiO2 electrode, showing the dynamic formation of a catalytically active dimer on an electrode surface. Finally, we combined the light‐protected TiO2|MnP cathode with a CdS‐sensitized photoanode to enable solar‐light‐driven CO2 reduction with the light‐sensitive MnP catalyst.