Efficient Photoelectrochemical Reduction of Carbon Dioxide on a p-Type Silicon (p-Si) Electrode Modified with Very Small Copper Particles

The photoelectrochemical reduction of CO2 was performed with p-type silicon (p-Si) electrodes modified with very small Cu particles. Hydrocarbons such as methane and ethylene were produced together with CO and HCOOH similar to the case of a Cu-metal electrode, but at potentials ca. 0.4 V more positive than the Cu-metal electrode, clearly showing that the photovoltage generated in the p-Si is effectively utilized for the CO2 reduction. On the contrary, p-Si electrodes coated with continuous Cu layers as well as naked p-Si electrodes showed no such photo-shifts in potential.