A versatile photoanode-driven photoelectrochemical system for conversion of CO2 to fuels with high faradaic efficiencies at low bias potentials

A photoanode-driven photoelectrochemical system consisting of a WO3 photoanode under bias potential and Cu or Sn/SnOx as the cathode for the reduction of CO2 has been studied under visible light irradiation. The bias potentials typically required for the onset of Oxygen evolution current at the photoanode were sufficient for the efficient reduction of CO2 at the metallic/composite counter electrodes. Using Cu as a cathode electrocatalyst, faradaic efficiencies of 67% for CH4 and 71.6% for all carbon-containing products were achieved. With Sn/SnOx, a combined faradaic efficiency (CO + HCOOH) of 44.3% was obtained at + 0.8 V. The 2-electrode potential between the counter electrode and working electrode for the WO3 driven system was less than the lowest bias potential reported so far for conventional photocathode-driven systems. The results demonstrate for the first time that the intrinsically more stable photoanode-driven systems could accomplish the reduction of CO2 with higher efficiencies relative to the conventional photocathode-driven systems.