Ligand modulation of active interfaces to promote photoelectrochemical water splitting

Although the construction of semiconductor/transition-metal oxyhydroxide (SC/TMOOH) system represents a promising approach for boosting photoelectrochemical (PEC) water splitting performance, persistent challenges including inevitable interface charge recombination and sluggish water oxidation kinetics continue to hinder the improvement of PEC performance. Here, a rational ligand modulation strategy is developed to optimize the PEC activity of SC/TMOOH system through coordinating 2-methylimidazole (2MI). As a result, BiVO₄/FeOOH-2MI achieves unprecedented PEC efficiency, exhibiting an outstandingly high photocurrent density of 6.57 mA/cm² at 1.23 V vs. reversible hydrogen electrode (RHE) along with long-term durability. Density functional theory (DFT) in combination with in situ ultraviolet/visible spectroelectrochemistry (UV/vis-SEC) indicates that the coordination of the 2MI modulates interfacial behavior at both the SC/TMOOH and TMOOH/electrolyte interfaces. Specifically, it not only significantly boosts the kinetics of hole transfer, but alleviates the strong adsorption on Fe sites. Moreover, the 2MI molecule can be utilized to create alternative SC/TMOOH systems, for instance, BiVO₄/NiOOH-2MI and BiVO₄/CoOOH-2MI, to improve the PEC performance. This study presents an innovative ligand modulation strategy for highly efficient PEC water splitting.