A novel hierarchical 0D/3D NH2-MIL-101(Fe)/ZnIn2S4 S-scheme heterojunction photocatalyst for efficient Cr(VI) reduction and photo-Fenton-like removal of 2-nitrophenol

Abstract

In this work, we designed a new hierarchical 0D/3D NH2-MIL-101(Fe)/ZnIn2S4 (NM-101(Fe)/ZIS) S-scheme heterojunction photocatalyst using a simple oil bath technique, in which nanometer-sized NM-101(Fe) are extensively scattered on the surface of ZIS microspheres. In contrast to an acidic environment, the optimal 10% NM-101(Fe)/ZIS can remove 94% of Cr(VI) in 60 min under neutral circumstances, the apparent rate constant is 24.6 and 3.26 times that of NM-101(Fe) and ZIS, respectively. This is due to the hierarchical 0D/3D heterostructure and the unique S-scheme photogenerated carrier transfer path, which successfully encourage the separation of photogenerated carriers while simultaneously enhancing redox ability. Specially, an efficient photo-Fenton-like system was developed using Fe3+ in NM-101(Fe) in conjunction with external H2O2 for entirely eliminating the refractory 2-nitrophenol pollutant in 120 min. It has an apparent rate constant that is 5.63 and 3.99 times that of pure NM-101(Fe) and ZIS. In order to better meet the demands of practical wastewater treatment, the impact of various photocatalyst doses, initial solution concentrations, coexisting ions and pH values on its photocatalytic activity were investigated. Finally, this work provides an idea to construct unique 0D/3D S-scheme heterostructure and effective photo-Fenton-like system for photocatalytic water purification.