g-C3N4 modified by cobalt–nickel bimetallic phosphide for highly efficient photocatalytic removal of methylene blue

Graphitic carbon nitride (gCN) has shown great potential in photocatalysis. Developing suitable cocatalysts is a critical way to enhance gCN's photocatalytic performance. In this paper cobalt–nickel bimetallic phosphide (CoNiP) was used as a cocatalyst to modify gCN. A gCN/CoNiP composite was successfully prepared by a simple hydrothermal method. XRD, XPS, SEM, UV-vis DRS, and PL characterization studies showed that a Schottky junction-like structure was constructed between gCN and CoNiP, which intensified the visible light response, enhanced the charge transfer rate and prohibited the recombination of photogenerated carriers, thus significantly improving gCN photocatalytic activity. Under simulated sunlight, the removal efficiency of methylene blue (10 mg L−1) was 97.8% by 120 min of irradiation, 44.6% higher than that of gCN. The quenching experiment showed that ˙O2−, ˙OH and h+ were the main active species. Based on the above points, the possible mechanism of photocatalysis was deduced.