Photoelectrochemical response of Au-decorated CuBi2O4 photocathode in bicarbonate solution

Abstract

Photoelectrochemical CO2 reduction is considered an environmentally and economically sustainable method for carbon sequestration to mitigate the impact of global warming. However, no practical photocatalytic system has been developed despite the urgent need for efficient CO2 reduction. CuBi2O4 is a p-type metal oxide semiconductor with a band-gap of similar to 1.8 eV. The conduction and valence band positions of CuBi2O4 are approximately - 0.9 and 0.9 V vs normal hydrogen electrode (NHE) at pH 7, respectively, which makes the metal oxide semiconductor a promising photoelectrode for CO2 reduction. The fabricated CuBi2O4 electrode displays a photocurrent of similar to 0.3 mA/cm(2) at 0.2 V vs NHE for facile peroxide reduction. However, the photocurrent reduces to 60 mu A/cm(2) in CO2 -saturated 0.1 M KHCO3 aqueous solution and the electrode undergoes fast photo-decomposition. In order to enhance the surface reaction kinetics, a Au electrocatalyst is formed on the CuBi2O4, which increases twice the photocurrent. Further, we have employed the tip collection/substrate generation mode of scanning electrochemical microscopy to collect the photogenerated species on the Au-decorated CuBi2O4 surface. The electrochemical characterizations clearly manifest the necessity of using effective electrocatalysts, such as Au, for photoelectrochemical reduction in a bicarbonate solution.