Molybdenum-modified ZnIn2S4 with a bifunctional cocatalyst for efficient photocatalytic overall water splitting under simulated sunlight

Abstract

Photocatalytic overall water splitting (POWS) is a promising technique for sustainable hydrogen production that can potentially tackle the current energy and environmental challenges. As a visible-light-active photocatalyst, ZnIn₂S₄ is an ideal candidate for POWS; however, it exhibits low efficiency due to poor charge separation and improper surface reactions. Here, ZnIn₂S₄ was modified by doping Mo and depositing a bifunctional cocatalyst for efficient POWS under sunlight. Charge separation and photodeposition of Pt and CrO_x were accelerated by Mo introduction to promote surface POWS reactions and suppress reverse reactions. Under simulated sunlight irradiation, the modified ZnIn₂S₄ achieved POWS with an apparent quantum efficiency (AQE) of 0.17% at 420 ± 20 nm and a solar-to-hydrogen (STH) conversion efficiency of 0.016%. Theoretical calculations indicated that Mo dopants introduced spin-polarized states at both the conduction band bottom and the valence band top, which are spin-forbidden for charge recombination. This study served as a useful guideline for the design and development of efficient photocatalysts for sunlight-driven POWS.