Anionic polyacrylamide-assisted construction of thin 2D-2D WO3/g-C3N4 Step-scheme heterojunction for enhanced tetracycline degradation under visible light irradiation

[Display omitted] •2D-2D WO3/g-C3N4 S-scheme heterojunction (C–W/N) is successfully synthesized by straight-forward calcination method.•C–W/N exhibits thin planar structure with oxygen vacancies, fast charge transfer and enhanced quantum efficiency.•C–W/N displays the significant photocatalytic performance in tetracycline (TC) degradation under visible-light irradiation.•The possible photocatalytic mechanisms of TC degradation by C–W/N is proposed. Thin 2D/2D WO3/g-C3N4 Step-scheme (S-scheme) heterojunction with carbon doping and bridge (C–W/N) was constructed with anionic polyacrylamide (APAM), in which APAM functioned as an assistant templet and a carbon source. APAM and WO3 were inserted into g-C3N4 nanosheet. The carbon, thin planar structure and WO3 with oxygen vacancies result in fast charge transfer, high quantum efficiency and strong driving force for photocatalytic reaction. Consequently, as-prepared C–W/N ternary composite photocatalyst exhibited significantly enhanced photocatalytic performance for tetracycline (TC) degradation under visible light compared to pure g-C3N4, WO3 and other binary composites. Moreover, the material showed high stability and reusability in cyclic TC degradation. The principal intermediate products over C–W/N photocatalyst were revealed by HPLC-MS analysis. Corresponding degradation pathway of TC was also presented in this work. According to the trapping experiments, analysis of electron spin resource (ESR) and band gap, possible charge transfer pathways of C–W/N are proposed and discussed in detail. Based on the results, carbon derived from APAM works not only as electron mediator but also as acceptor for photocatalytic degradation reaction. It is a promising way to further modulate heterojunction for varies applications.