Modulation of charge-transfer behavior via adaptive interface treatment for efficient photoelectrochemical water splitting

Abstract

The integration of a transition metal hydroxide (TMH) and semiconductor (SC) is a promising approach for improving photoelectrochemical (PEC) water oxidation. However, charge recombination at the SC/TMH interface is inevitable. Herein, a desirable charge-separation system was obtained through a simple acid-etching strategy (i.e., hydrochloric acid, HA) in the SC/TMH coupling system. Optimized BiVO₄-HA/FeNi(OH)_X exhibited a photocurrent density of 4.7 mA cm⁻² at 1.23 V versus the reversible hydrogen electrode (RHE), which was 4.4-times higher than that of pure BiVO₄ and 1.8-times higher than that of BiVO₄/FeNi(OH)_X, respectively. Systematic studies revealed that a considerably enhanced photocurrent could be determined by three main factors: (1) formation of an adaptive interface by enhanced hydrophilicity boosted hole-transfer kinetics and suppressed interface recombination; (2) reducing the density of surface states; (3) the shortened distance of the hole from the bulk to the surface. Importantly, this strategy could be extended to other TMH (CoNi(OH)_X and CoFe(OH)_X), showing its universality. This work opens up opportunities in interfacial engineering of SC/TMH systems for efficient PEC water splitting.