Construction of 2D/2D protonated g-C3N4 /BiOBr heterojunction composite with high photocatalytic degradation performance

In this study, protonated g-C3N4 nanosheets (PCNS) were firstly synthesized through the thermal polymerization of melamine, thermal exfoliating of g-C3N4, and the protonating of g-C3N4 nanosheets. Then, 2D/2D g-C3N4/BiOBr heterojunction composites (PCNSB-X, X = 10, 20, 30, 50, 70, representing the mass percent of PCNS in the composites) were constructed by the in-situ growth of BiOBr nanosheets on the surface of PCNS. PCNSB-X composites showed enhanced light absorption, reduced recombination rate of photogenerated electron-hole pairs, higher photocurrent density and decreased impedance. Their photocatalytic activities toward degrading Rhodamine B (RhB) aqueous solution showed a trend of gradually increasing and then decreasing with the increase of g-C3N4 nanosheet dosage. The optimum photocatalytic performance was achieved by PCNSB-50, who (0.05 g) degraded 98.8 % of RhB molecules (100 mL, 20 mg/L) after 60 min of visible light irradiation. Its reaction rate constant (k=0.0717 min(-1)) was 7.03 and 2.82 times that of pure g-C3N4 nanosheets and pure BiOBr nanosheets, respectively. g-C3N4/BiOBr composites also exhibited excellent recyclability and stability for degrading RhB. This work provides a feasible method for synthesizing g-C3N4/BiOBr composites with excellent photocatalytic performance.