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

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.