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 photo generated 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 x 10(-4) min(-1) (R-2 = 0.994) and 7.94 x 10(-4) min(-1) (R-2 = 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. (C) 2018 Elsevier Inc. All rights reserved.