Enhanced photoelectrocatalytic degradation of norfloxacin by an Ag3PO4/BiVO4 electrode with low bias

In this work, an Ag3PO4-modified BiVO4 electrode was prepared on an FTO substrate and used as a photoanode for photoelectrocatalytic degradation of organic contaminants. The photocurrent generated from the synthesized Ag3PO4/BiVO4 photoelectrode under visible light irradiation was more than twice that from pure the BiVO4 electrode, which could be attributed to the lower recombination rate of the photogenerated electron–hole pairs of the Ag3PO4/BiVO4 photoanode, as proved by the electrochemical impedance spectroscopy and photoluminescence spectra. The Ag3PO4/BiVO4 electrode was effective for the oxidation of organic pollutants in photoelectrocatalysis systems at relatively low bias potentials. A higher photoelectrocatalytic activity for norfloxacin degradation was observed when the Ag3PO4/BiVO4 electrode was than with the BiVO4 electrode, where norfloxacin with an initial concentration of 5 mg/L could be degraded within 90 min. The apparent rate constants of norfloxacin degradation using a BiVO4 electrode and Ag3PO4/BiVO4 are estimated to be 2.83 × 10−4 min−1 (R2 = 0.994) and 7.94 × 10−4 min−1 (R2 = 0.996), respectively. Analysis of the degradation intermediates indicated that the piperazine ring and the carboxyl group of the norfloxacin were attacked during the degradation process. The Ag3PO4/BiVO4 photoanode was also proved to be effective for the degradation of two other antibiotics, sulfamethoxazole and oxytetracycline.