Photoanode driven photoelectrocatalytic system for CO2 reduction to formic acid by using CoOx cathode

Abstract

The reduction of CO2 to produce fuels is considered as a promising way to reduce CO2 emission and address energy crisis. Due to the high efficiency and direct usage of solar energy, photoelectrocatalysis (PEC) and electrocatalysis (EC) have attracted wide interests from the researchers. In this work, a highly efficient nanosheet-like CoOx (cathode)-TiO2 nanotube arrays (TNTs, anode) photoelectrocatalytic system was constructed for reducing CO2. Nanosheet-like CoOx was coated on the surface of copper foam via electrodeposition. Electrocatalysis measurements show that the as-prepared CoOx cathode has an optimal performance for CO2 electro-reduction to formic acid with a Faradic efficiency of 60.9% at −0.85 V (vs. Ag/AgCl). Combined with TNTs photoanode, photoanode driven PEC system was constructed for the direct usage of solar energy for CO2 reduction. Compared with EC system, such PEC system displays a high formic acid yield of 56.6 μmol/cm2h at a low applied potential. Moreover, coating a thin ZnO layer as a protective layer was applied to improve the stability performance of the bare CoOx cathode by using the method of atomic layer deposition technology. This work provides a promising strategy for developing a high efficient CO2 reduction system directly using solar energy by combining electrocatalyst and photoanode.