Synthesis and characterization of a heterojunction rGO/ZrO2/Ag3PO4 nanocomposite for degradation of organic contaminants

Abstract

Synergy between surface adsorption and photocatalysis is key for effective contaminant degradation in the liquid phase. Herein, we report a heterojunction photocatalyst of reduced graphene oxide (rGO)/zirconium dioxide (ZrO2)/silver phosphate (Ag3PO4) that incorporates this synergy for 4-nitrophenol (PNP) removal. Compared with other photocatalyst combinations, ZrO2 and Ag3PO4 coupling generates reactive species with greater degradation potential. ZrO2 and rGO were synthesized by a green approach using a one-step hydrothermal reaction in ethanol-water. The growth of rGO/ZrO2 and Ag3PO4 were accomplished and the functions of each part were well developed together. The rGO/ZrO2/Ag3PO4 composite exhibited enhanced light absorption and a low band gap energy (2.3 eV) owing to rGO and Ag3PO4 integration. The composite's photocatalytic activity was much higher than that of ZrO2, Ag3PO4, or ZrO2/Ag3PO4. The maximal adsorption of PNP was 26.88 mg/g, and a pseudo-first-order model described the PNP degradation kinetics (k = 0.034 min(-1)). Synergy between the three components resulted in 97% PNP removal in 90 min, and even after five cycles, 94% PNP removal was obtained. The quantum yield of the system (7.31 x 10(-5) molecules/photon) was compared with those in previous reports to assess the photocatalytic performance and energy requirements.