Facile and robust construction of a 3D-hierarchical NaNbO3-nanorod/ZnIn2S4 heterojunction towards ultra-high photocatalytic H2 production

Abstract

It is imperative but still challenging to develop heterojunction photocatalysts for efficient interfacial charge carrier separation in photocatalytic hydrogen evolution (PHE) reactions. Encouragingly, in this work, we constructed a 3D hierarchical NaNbO₃/ZnIn₂S₄ heterojunction for the first time by in situ coating thin-layered ZnIn₂S₄ nanosheets on the external surface of NaNbO₃ nanorods via a facile solvothermal method. A striking hydrogen evolution rate of 30.04 mmol h⁻¹ g⁻¹ was attained using NaNbO₃/ZnIn₂S₄ as a photocatalyst under simulated sunlight irradiation, which is almost 110-fold and 11-fold higher than that of bare NaNbO₃ and ZnIn₂S₄, respectively, and is the highest value obtained thus far among reported NaNbO₃ and ZnIn₂S₄-based catalysts. This extraordinary improvement in the photocatalytic performance is mainly due to two reasons. Firstly, the difference in conduction band position and the intimate contact between NaNbO₃ and ZnIn₂S₄ facilitate interfacial charge separation from NaNbO₃ to ZnIn₂S₄. Secondly, the unique hierarchical heterostructure not only affords a more diffused surface area but also serves as a 3D supporting platform to generate more fruitful proton reduction sites, realizing a maximized photocatalytic activity. Additionally, density functional theory (DFT) calculations on the heterojunction further revealed the electron density distribution at the heterointerface and a close-to-neutral Gibbs free energy of hydrogen adsorption (ΔG_H). Hence, the present work can provide fresh guidance for the synthesis and development of more NaNbO₃ and ZnIn₂S₄-based composite photocatalysts for related applications in photocatalysis.