Dual enhancement of capturing photogenerated electrons by loading CoP nanoparticles on N-deficient graphitic carbon nitride for efficient photocatalytic degradation of tetracycline under visible light

[Display omitted] •CoP/CNx composite photocatalysts were rationally designed and synthesized.•CoP/CNx composite show enhanced photocatalytic degradation of TC.•The possible photodegradation pathways of TC was proposed.•The N-defects and CoP co-catalyst synergistically promoted the charge separation efficiency. The strategies of introducing defect engineering and cocatalysts in designing photocatalysts are both effective at ameliorating photocatalytic activity. In this study, N-defected g-C3N4 (CNx) was added to the preparation process of CoP, where N-defects and loaded CoP cocatalyst were successfully combined to synthesize CoP/CNx composite photocatalysts, which not only strongly expands the visible-light absorption but also effectively restrains the recombination of photoinduced electron holes, hence greatly improving the photocatalytic degradation performance of tetracycline (TC). Experimental results revealed that 5% CoP/CNx has the optimum photocatalytic activity with a degradation rate of 97% within 120 min of visible-light irradiation, which is 6.84 and 4.33 times higher than that of bare CN and CNx, respectively. In addition, the cycling experiments and XRD patterns before and after the photocatalytic reaction showed that the catalyst exhibits outstanding stability, which is conducive to practical applications in the field of photocatalysis. The possible photodegradation pathways of TC were proposed on the basis of the intermediates detected by liquid chromatography-mass spectroscopy (LC–MS). The N-defects in the CN structure and the addition of the cocatalyst CoP synergistically promoted the separation efficiency of the photogenerated charges of the composite and enhanced its photocatalytic activity.