H2O2 assisted photoelectrocatalytic degradation of diclofenac sodium at g-C3N4/BiVO4 photoanode under visible light irradiation

•g-C3N4/BiVO4 composite photoanode was prepared by electrospinning method.•g-C3N4/BiVO4 photoanode exhibited a higher activity than g-C3N4 or BiVO4 photoanode.•Added H2O2 enhanced the photoelectrocatalytic oxidation of diclofenac efficiently.•The main active species in the PEC system were determined to be OH and O2−.

In this paper, g-C3N4/BiVO4 composite was electrospinned onto FTO substrate and used as photoanode for photoelectrocatalytic degradation of diclofenac sodium. The photoelectrocatalytic degradation efficiency of DCF by the g-C3N4/BiVO4 photoanode is much higher than that by the individual g-C3N4 and BiVO4 photoanodes. The first order kinetic constants are estimated to be 3.2 × 10−3 min−1 for g-C3N4/BiVO4 photoanode, while the kinetic constants are 1 × 10−4 min−1 and 1.1 × 10−3 min−1 for g-C3N4 and BiVO4 photoanode. To further increase the degradation of DCF in PEC process, H2O2 was added into the system, and the results indicated that DCF degradation was largely increased. The kinetic rate constant was 5.6 × 10−3 min−1 for H2O2 assisted PEC process and it was estimated to be 3.2 × 10−3 min−1 and 1 × 10−5 min−1 for the individual PEC process and H2O2 oxidation process, respectively. Effect of initial pH, H2O2 dosage and applied bias on DCF degradation was investigated in detail. The highest DCF degradation efficiency was achieved at initial pH of 3.17 and applied bias potential of 1.0 V (vs. SCE) with 10 mM H2O2 addition. Involved reactive active species were studied using electron spin resonance; a proposed reaction pathway was proposed.

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