Oxygen-Defect-Mediated ZnCr2O4/ZnIn2S4 Z-Scheme Heterojunction as Photocatalyst for Hydrogen Production and Wastewater Remediation

Photocatalysis has long been considered a promising technology in green energy and environmental remediation. Since the poor performance of single components greatly limits the practical applications, the construction of heterostructures has become one of the most important technical means to improve the photocatalytic activity. In this work, based on the synthesis of oxygen-vacancy-rich ZnCr2O4 nanocrystals, ZnCr2O4/ZnIn2S4 composites are prepared via a low-temperature in situ growth, and the oxygen-vacancy-induced Z-scheme heterojunction is successfully constructed. The unique core-shell structure offers a tight interfacial contact, increases the specific surface area, and promotes the rapid charge transfer. Meanwhile, the oxygen-vacancy defect level not only enables wide-bandgap ZnCr2O4 to be excited by visible light enhancing the light absorption, but also provides necessary conditions for the construction of Z-scheme heterojunctions promoting charge separation and migration and allowing more reactive charges. The reaction rates of visible-light-driven photocatalytic hydrogen production (3.421 mmol g-1 h-1), hexavalent chromium reduction (0.124 min-1), and methyl orange degradation (0.067 min-1) of the composite reach 3.6, 6.5, and 8.4 times those of pure ZnIn2S4, and 15.8, 41.3, and 67.0 times those of pure ZnCr2O4, respectively. This work presents a novel option for constructing high-performance photocatalysts.

Automated summary

Photocatalysis is a promising technology in green energy and environmental remediation. The construction of heterostructures is important to improve the photocatalytic activity. In this work, ZnCr2O4/ZnIn2S4 composites with an oxygen-vacancy-induced Z-scheme heterojunction are successfully prepared, which offers tight interfacial contact and promotes rapid charge transfer. The composite shows significantly enhanced photocatalytic activity compared to pure ZnIn2S4 and ZnCr2O4 in hydrogen production, hexavalent chromium reduction, and methyl orange degradation.