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

Abstract

A photoanode-driven photoelectrochemical system consisting of a WO₃ photoanode under bias potential and Cu or Sn/SnO_x 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/SnO_x, 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.