A simple strategy to refine CuO photocatalytic capacity for refractory pollutants removal: Roles of oxygen reduction and Fe(II) chemistry.

Visible-light-driven photocatalysis is a promising technology for advanced water treatment, but it usually exhibits a low efficiency. CuO is a low-cost semiconductor with narrow band gap, high absorption coefficient and suitable conduction band, but suffers from low charge mobility, poor quantum yield and weak catalytic performance. Herein, the CuO catalytic capacity for refractory pollutants degradation is drastically improved by a simple and effective strategy. By virtue of the synergistic effects between photocatalysis and Fenton, a novel and efficient photocatalysis-driven Fenton system, PFC, is originally proposed and experimentally validated using CuO/Nano-C hybrids. The synergistic PFC is highly Nano-C-dependent and exhibits a significant superiority for the removal of rhodamine B and p-nitrophenol, two typical refractory pollutants in wastewater. The PFC superiority is mainly attributed to: (1) the rapid photo-electron transfer driven by Schottky-like junction, (2) the selective O reduction mediated by semi-metallic Nano-C for efficient HO generation, (3) the specific HO activation and large OH generation catalyzed by Haber-Weiss Fenton mechanism, and (4) the accelerated Fe/Fe cycling and robust Fe regeneration via two additional pathways. Our findings might provide a new chance to overcome the intrinsic challenges of both photocatalysis and Fenton, as well as develop novel technology for advanced water treatment.