Interface-Confined Surface Engineering via Photoelectrochemical Etching toward Solar Neutral Water Splitting

Abstract

Photogenerated electron–hole recombination arising from the interface/surface among semiconductor/cocatalyst/electrolyte becomes prominent for photoelectrochemical (PEC) water splitting, which principally retards the charge transfer pathways and reduces the oxygen reaction kinetics, especially in a neutral environment. Herein, interface-confined surface engineering via a PEC reduction strategy was carried out on a semiconductor/transition metal oxide system in a neutral electrolyte, which can remove the interfacial charge recombination and mediate the charge transfer pathways, and importantly stabilize the semiconductor for a long-term operation. Surface-confined CoMoO4–x/BiVO4 exhibits a current density of 3.5 mA cm–2 at 1.23 VRHE under 1 sun irradiation with an excellent stability for 20 h in 0.5 M Na2SO4, showing one of the best photocorrosion resistance performances among BiVO4 photoelectrodes under near-neutral pH conditions. A comparable PEC activity and stability were achieved using pristine BVO, CoOx/BiVO4, and MoOx/BiVO4 with the PEC etching, which clarify the mechanism of the reduced barrier layer and the defected CoMoO4–x catalysts in boosting the charge transfer efficiency and stabilizing BiVO4. Meanwhile, CoOx acts as a promoter enhancing PEC activity and MoOx acts as a passivation layer protecting the semiconductor from photocorrosion. This work sheds light on that the interface-confined surface modification plays an essential role in modulating the charge transfer pathways, especially for a reaction occurring on a surface, which may lead to a new direction of using a neutral environment for high-performance photoelectrode design toward achieving efficient solar energy conversion.