Boosting solar water oxidation activity and stability of BiVO4 photoanode through the Co-catalytic effect of CuCoO2

Abstract The poor surface charge separation and transfer properties as well as sluggish water oxidation kinetics jointly limit the performance of BiVO 4 photoanode for water oxidation. In this work, p-type CuCoO 2 with high-spin Co 3+ (Oh) was investigated as co-catalyst to synergistically improve the surface charge separation and transfer efficiencies as well as reaction kinetics of BiVO 4 film for photoelectrochemical water oxidation. In comparison with the photocurrent on BiVO 4 photoanode for water oxidation (1.21 mA/cm 2 at 1.23 V vs. RHE), the CuCoO 2 -coupled BiVO 4 (CuCoO 2 /BiVO 4 ) photoanode exhibits a higher photocurrent density of 3.32 mA/cm 2 at 1.23 V vs. RHE under AM 1.5G illumination. In addition, a significant improvement on the reaction stability is achieved on the CuCoO 2 /BiVO 4 photoanode, about ∼79% water oxidation activity is retained on the CuCoO 2 /BiVO 4 photoanode after operating at 0.8 V vs. RHE for 5 h, while only ∼9% activity is retained on the BiVO 4 photoanode. The boosted water oxidation activity and stability on CuCoO 2 /BiVO 4 photoanode could be attributed the synergistic effect that originated from CuCoO 2 -electrocatalysis and BiVO 4 -photocatalysis in thermodynamics and kinetics. Specifically, p-n heterojunctions are formed in the coupling interface between CuCoO 2 (p-type) and BiVO 4 (n-type), which thermodynamically improve the surface charge separation and transfer efficiencies of BiVO 4 photoanode during water oxidation. Simultaneously, the high-spin Co 3+ (Oh) of CuCoO 2 could act as active sites to accelerate the water oxidation of CuCoO 2 /BiVO 4 photoanode in kinetics. In addition, Cu 2+ active sites are formed for water oxidation through the oxidation reaction of photogenerated holes with the Cu + of CuCoO 2 .