Carbonate-coordinated cobalt co-catalyzed BiVO4/WO3 composite photoanode tailored for CO2 reduction to fuels

Abstract

We report here that cobalt carbonate (Co-Ci) is a tailored oxygen evolution electrocatalyst (OEC) from water on BiVO4/WO3 composite photoanode to drive photoelectrochemical reduction of CO2 to fuels on a Cu cathode. For water oxidation, Co-Ci/BiVO4/WO3 performed best in CO2-saturated KHCO3 (KCi, pH 7) electrolyte recording an exceptional photocurrent of 3.5mA/cm2 at 1.23VRHE under 1sun illumination, and an onset potential of 0.2VRHE. In the photoanode-driven CO2 reduction, the Co-Ci/BiVO4/WO3 (photoanode)-Cu (cathode) system showed stable photocurrent and 51.9% faradaic efficiency (against water reduction to H2) for CO and C1-C2 hydrocarbons, whereas the best known OEC cobalt phosphate (Co-Pi) was less stable and gave only 22.4% faradaic efficiency. Due to its high stability and CO2 reduction selectivity, the Co-Ci assisted system produced 11 times larger amount of CH4 than the Co-Pi assisted system in a continuous operation. © 2015.