Z-Scheme mechanism study of ternary BiPO4/reduced graphene oxide/protonated g-C3N4 photocatalyst with interfacial electric field mediating for the effective photocatalytic degradation of tetracycline

Z-scheme heterojunction research has become a hotspot in the field of photocatalysis owing to the strong oxidative and reductive capacity for driving photocatalytic reactions. In this work, for the first time, a Z-scheme ternary bismuth phosphate/reduced graphene oxide/protonated g-C₃N₄ (BiPO₄/rGO/pg-C₃N₄) photocatalyst was fabricated for photocatalytic degradation of tetracycline (TC). The optimal mass ratios of rGO and pg-C₃N₄ were confirmed as 1.2 wt% and 40 wt%, respectively. This Z-scheme heterojunction exhibited an enhanced TC degrading ability with an 80.0% of TC decomposition after 50 min simulated solar light irradiation, which was 3.3 and 6.3 times that of pg-C₃N₄ and BiPO₄, respectively. Importantly, the internal electric field forced Z-scheme charge transfer of BiPO₄/rGO/pg-C₃N₄ composites, possessing higher charge separation efficiency. The formation of the Z-scheme heterojunction was substantiated by radical scavenging experiments and Mott–Schottky measurements, and it was beneficial for the photocatalytic reaction by accelerating the charge separation and improving the redox ability. Moreover, rGO as cocatalyst could not only provide TC adsorption and catalytic sites but also further promote the charge transfer.