The effects of bismuth (III) doping and ultrathin nanosheets construction on the photocatalytic performance of graphitic carbon nitride for antibiotic degradation

To further enhance the photocatalytic performance of graphitic carbon nitride (g-C 3 N 4 ), we rationally combined two strategies (foreign metal doping and ultrathin nanosheet construction) to synthesize bismuth (III) (Bi 3+ ) doped ultrathin g-C 3 N 4 nanosheets (Bi-CNNS) via one-step thermal polymerization method using melamine as the raw material, bismuth nitrate pentahydrate (Bi(NO 3 ) 3 ·5H 2 O) as the dopant source, and nitric acid (HNO 3 ) and acetic acid (AC) as soft templates for the ultrathin nanosheets construction. The Bi-CNNS catalysts exhibited an excellent photocatalytic performance in tetracycline (TC) degradation. The TC removal efficiency reached to be 94.1% in 30 min under visible-light irradiation over 0.03Bi-CNNS, which is 6.03 times higher than that of pure g-C 3 N 4 (CN). The higher specific surface area, narrower bandgap, the improved photoexcited electron-hole pair transfer and separation efficiency, and prolonged carrier lifetimes in the Bi 3+ -doped ultrathin g-C 3 N 4 nanosheets led to a significantly enhanced photocatalytic performance. The main radical species responsible for the degradation of tetracycline over 0.03Bi-CNNS were O 2 − and OH. Moreover, the possible photodegradation intermediate products of TC were detected by gas chromatography–mass spectroscopy (GC–MS), and a possible pathway was proposed.