Bismuth-Decorated Silicon Photocathodes for CO₂-to-Formate Solar-Driven Conversion

The integration of metal-based catalysts onto semiconducting electrodes provides a real benefit for the CO(2)electrochemical conversion because it allows the electrochemical process to be activated by photogenerated electrons. In that context, we report here that silicon photocathodes modified with electrodeposited Bi nanostructures are highly active for the photoelectrocatalytic conversion of CO(2)to formate. Through the consumed electrical charge and the electrodeposition time, it is possible to finely control both the structure and the density of the deposited catalyst. The optimal photocathode was prepared by using a 5 s electrodeposition time and exhibited the highest photocurrent density (-24.1 mA cm(-2)) with partial formate photocurrent densityj(formate)=-17.4 mA cm(-2)at -1.03 V vs Reversible Hydrogen Electrode (RHE), i. e. a 0.84 V overpotential for CO(2)to formate conversion in CO2-saturated 0.5 M KHCO(3)solution. Such values highlight the excellent photoelectrocatalytic activity of our photocathodes.