Heterojunction ZnWO4/ZnFe2O4 composites with concerted effects and integrated properties for enhanced photocatalytic hydrogen evolution

Abstract

Hydrogen fuel generated via solar water splitting has been recognized as a promising green energy technique. In this study, a novel ZnWO₄/ZnFe₂O₄ heterojunction composite was successfully prepared using a facile co-precipitation method for photocatalytic hydrogen evolution without using a noble metal co-catalyst. The as-prepared composites were well-characterized using PXRD, UV-vis-DRS, TEM and XPS to ascertain the successful deposition of the ZnFe₂O₄ nanoparticles onto the ZnWO₄ flakes. During the photocatalytic hydrogen evolution experiments using Na₂S and Na₂SO₃ as hole scavengers, ZnWO₄/ZnFe₂O₄ (30 wt%) exhibited the best activity as compared to pure ZnWO₄ and ZnFe₂O₄. The underlying reasons for the superior photocatalytic hydrogen evolution of the optimal composite were assessed based on the inextricably linked factors of light absorption, mobility and separation of charge carriers, and redox potentials using photoluminescence, time-resolved fluorescence lifetime and electrochemical impedance spectroscopy measurements. The photochemical durability of the ZnWO₄/ZnFe₂O₄ heterojunction composite signifies its suitability for practical applications.