G-C3N4/Carbon doped ammonium phosphotungstate heterojunction with pyromellitic diimide as organic electron mediator for efficient acetamiprid photocatalytic degradation

Abstract

The high recombination of photogenerated electron-hole pairs and low redox ability in single photocatalysts are still challenges in improving photocatalytic degradation efficiency. In this research, carbon-doped ammonium phosphotungstate (CNPW) was successfully loaded on the surface of g-C3N4 with pyromellitic diimide (PMDI) as the new kind of organic electron mediator. The photocatalytic degradation rate constant k for acetamiprid of g-C3N4/PMDI/CNPW under visible light is 0.528 h−1 which is about 13.2 and 24 times higher compared with g-C3N4 and CNPW, respectively. We demonstrate the photogenerated charge carriers of g-C3N4/PMDI/CNPW obey the Z-scheme heterojunction mechanism rather than the type-Ⅱ heterojunction mechanism. PMDI can efficiently reduce the recombination of electron-hole pairs and enhance the photocatalytic degradation ability in the Z-scheme system. Furthermore, we have found that urea can act as a protective agent to protect g-C3N4 from decomposing in synthesizing g-C3N4/PMDI/CNPW. This research provides a new strategy for synthesizing high redox ability Z-scheme heterojunction. Introducing PMDI as an organic electron mediator enables a new pathway for enhancing photogenerated charge carriers transferring in a Z-scheme heterojunction system.