Visible-light-responsive S-vacancy ZnIn2S4/N-doped TiO2 nanoarray heterojunctions for high-performance photoelectrochemical water splitting

Abstract

The invention and design of defect-engineered heterojunctions (DEHs) has been considered an emerging prospect to achieve effective carrier separation and electron transport in hybrid nanocomposites, providing an innovative way to realize efficient solar-fuel production and achieve sustainable energy development. Introducing a desirable interfacial chemical bond via defect engineering is crucial to improve the electron transfer in photocatalysts. Herein, visible-light-responsive S-vacancy ZnIn₂S₄/N-doped TiO₂ (S_v-ZIS/N–TiO₂) nanoarrays were synthesized for enhancing photoelectrochemical (PEC) water splitting. Under simulated sunlight exposure, the S_v-ZIS/N–TiO₂ heterostructured photoanode could produce a photocurrent density of 4.9 mA cm⁻² at an external potential of 1.23 V vs. RHE in a 0.5 M Na₂SO₄ electrolyte and this DEH achieved an excellent PEC hydrogen evolution rate of 49.59 mmol g⁻¹ h⁻¹. The IPCE of the photoanode device is ∼57.9% at 350 nm and ∼7.3% at 400 nm. The enhanced photocatalytic activity of one-dimensional TiO₂ nanoarrays decorated with ZnIn₂S₄ quantum dots was attributed to the enhanced carrier separation, high charge transfer efficiency and improved carrier lifetime achieved as a result of the effective introduction of defective sites on the heterojunction.