Incorporation of sulfur vacancies in the ZnIn2S4 photoanode for highly efficient photoelectrochemical water splitting and urea oxidation

Abstract

Sluggish water oxidation kinetics and rapid charge recombination severely hinder the photoelectrochemical (PEC) water splitting performance of the ZnIn₂S₄ (ZIS) photoanode. Herein, a simple annealing strategy to rationally modulate sulfur vacancies (Sv) in the ZIS photoanode is developed, and the optimized ZIS-Sv-2h photoelectrode exhibits a remarkable photocurrent density of 2.18 mA cm⁻² at 1.23 V (vs. the reversible hydrogen electrode (RHE), AM 1.5 G), achieving a low onset potential of 0.14 V_RHE. Systematic electrochemical studies and dynamics analysis reveal that the sulfur vacancies (Sv) not only enhance the oxygen evolution reaction (OER) kinetics but also improve the charge separation. More importantly, compared with the former, the latter plays a vital role in achieving enhanced PEC water oxidation performance. In addition, the ZIS-Sv-2h also presents high PEC activity for urea oxidation (4.60 mA cm⁻² at 1.23 V_RHE). This work provides guidance for designing highly efficient photoelectrodes for solar-to-hydrogen conversion.