Synthesis of K-doped g-C3N4/carbon microsphere@graphene composite with high surface area for enhanced adsorption and visible photocatalytic degradation of tetracycline

Abstract

Abstract A novel potassium-doped g-C3N4/graphene/carbon microsphere (K-C3N4/CS@rGO) multi-heterojunction photocatalyst with enhanced photocatalytic activity was successfully synthesized by a simple chemical deposition method. The as-prepared K-C3N4/CS@rGO exhibits excellent photocatalytic activity with 92% removal of tetracycline (TC) under visible light illumination in 30 min, which is almost 3 times as high as that by the pure g-C3N4 (23% TC removal). Meanwhile, the kobs value (0.06185 min−1) of K-C3N4/CS@rGO was almost 6.5 times as high as that of pure g-C3N4 (0.00946 min−1).The preeminent photocatalytic performance under visible light is attributed to the following reasons: (1) the larger specific surface area (85.5267 m2 g−1) than the pure C3N4 (14.3478 m2 g−1); (2) extended visible light adsorption range as the doping of KBr; (3) the excellent electrical conductivity, and enhanced separation of charge carriers. Particularly, the synergic effect in cooperation with each other played an important role in heterogeneous photocatalyst. On the one hand, carbon microsphere and graphene can provide abundant oxygen-containing functional groups and reactive sites which increased adsorption of target pollution (from 10% to 31%) and dissolved oxygen, on the other hand, as the acceptor of electron transfer, carbon microsphere and graphene can provide broad transfer space for photogenerated electrons. In addition, the as-prepared K-C3N4/CS@rGO also exhibits remarkable stability and long-term recyclability, the degradation efficiency of tetracycline still above 85%. Meanwhile, this material was little affected by pH, the removal of tetracycline under different pH above 91%. These unique features of K-C3N4/CS@rGO suggest that it has good application future in the field of photocatalytic degradation of organic pollutant.