Incorporation of Sulfate Anions and Sulfur Vacancies in ZnIn₂S₄ Photoanode for Enhanced Photoelectrochemical Water Splitting

Abstract

Abstract Severe charge recombination and slow surface water oxidation kinetics seriously limit the practical application of ZnIn 2 S 4 photoanodes for photoelectrochemical water splitting. Herein, an in situ strategy to introduce sulfate (SO 4 2− ) anions and controlled bulk sulfur vacancies (S v ) into a ZnIn 2 S 4 photoanode is developed, and its PEC performance is remarkably enhanced, achieving a photocurrent density of 3.52 mA cm −2 at 1.23 V versus reversible hydrogen electrode ( V RHE ) and negatively shifted onset potential of 0.01 V RHE in phosphate buffer without a sacrificial agent under AM 1.5G illumination. The experimental characterizations and density functional theory calculations reveal that the SO 4 2− groups enhance the oxygen evolution reaction kinetics, while bulk S v improves the bulk carrier separation. The remarkable bulk carrier separation efficiency of 75.01% and surface carrier injection efficiency of 79.69% are achieved at 1.23 V RHE . This work provides a new route to design efficient photoanodes by the simultaneous manipulation of metal‐free anions and sulfur vacancies.