Construction dual vacancies to regulate the energy band structure of ZnIn2S4 for enhanced visible light-driven photodegradation of 4-NP

Most of the intrinsic photocatalysts with visible light response can only generate one active radical due to the limitation of their band structures, which is immediate cause limiting their photocatalytic degradation performance. In this work, ZnIn2S4 with Zn vacancy and S vacancy (VZn+S-ZnIn2S4) was prepared for the first time. As expected, the VZn+S-ZnIn2S4 exhibits remarkable photocatalytic performance for 4-Nitrophenol (4-NP) degradation under visible light and the apparent rate constant is about 11 times that of pristine ZnIn2S4. The construction of dual vacancies can regulate the energy band structure of the ZnIn2S4, enabling it to generate •OH and •O2- simultaneously. Meanwhile, dual vacancies system can also extremely improve the separation efficiency of carriers. It is worth noting that Zn vacancy and S vacancy can capture photogenerated holes and photogenerated electrons, respectively, which is beneficial for photogenerated carriers to participate in radical generation reactions. In addition, a possible 4-NP degradation pathway was proposed based on HPLC-MS analysis. This work provides a new way to construct photocatalysts for photodegradation of pollutants in wastewater.