Cr(VI) reduction over Ag3PO4/g-C3N4 composite with p-n heterostructure under visible-light irradiation

The graphitic carbon nitride/silver phosphate (Ag3PO4/g-C3N4) comPOsites were prepared through decorating Ag3PO4 nanoparticles on the g-C3N4 surface by a facile in-situ precipitation method. The as-prepared Ag3PO4/g-C3N4 photocatalysts demonstrated an enhanced absorption in the visible region and higher photo catalytic activity compared with the single-comPOnents for the Cr(VI) reduction under visible-light irradiation, suggesting that the dePOsition of Ag3PO4 nanoparticles on the pristine g-C3N4 enhanced the visible light absorption and photoreduction activity. It was confirmed that the separation efficiency of the Ag3PO4/g-C3N4 was more intensive than the pristine g-C3N4 and pure Ag3PO4 by photoluminescence spectra (PL), electrochemical impedance spectroscopy (EIS) and transient photocurrent (TPC) measurement. Nevertheless, more significant was the formation of p-n heterojunction structure between Ag3PO4 and g-C3N4, which efficiently promoted the diffusion and separation of electron-hole pairs and ultimately enhanced the Cr(VI) reduction performances. The p-n heterostructure Ag3PO4/g-C3N4(0.7) prepared at the Ag+/g-C3N4 mass ratio of 0.7 in the reaction system had the highest photocatalytic activity for the Cr(VI) reduction with 94.1% Cr(VI) removal efficiency in 120 min, which was 9.2-fold and 2.2-fold higher than those of the pristine g-C3N4 and Ag3PO4, respectively. This work found a new application of the Ag3PO4/g-C3N4 photocatalyst for heavy metal removal from wastewater. (c) 2020 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.