Synthesis and characterization of a heterojunction rGO/ZrO/AgPO nanocomposite for degradation of organic contaminants.

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 (ZrO)/silver phosphate (AgPO) that incorporates this synergy for 4-nitrophenol (PNP) removal. Compared with other photocatalyst combinations, ZrO and AgPO coupling generates reactive species with greater degradation potential. ZrO and rGO were synthesized by a green approach using a one-step hydrothermal reaction in ethanol-water. The growth of rGO/ZrO and AgPO were accomplished and the functions of each part were well developed together. The rGO/ZrO/AgPO composite exhibited enhanced light absorption and a low band gap energy (2.3 eV) owing to rGO and AgPO integration. The composite's photocatalytic activity was much higher than that of ZrO, AgPO, or ZrO/AgPO. 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). 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 × 10 molecules/photon) was compared with those in previous reports to assess the photocatalytic performance and energy requirements.