Enhanced Water Purification Efficiency Induced by Trace H<sub>2</sub>O<sub>2</sub> on the Electron Distribution-Polarized Unequilibrium Surface of CuS/ZnO Nanosheets
Tingting Gao, Hongqiang Wang, Jun Xu, Chun Hu, Lai Lyu
Abstract
Excessive chemical reagents and energy are necessary to maintain electron recycling in advanced oxidation processes, resulting in high-energy consumption for water purification. Here, we present a new dual-reaction center catalyst consisting of CuS/ZnO nanosheets (CS/ZO NSs) with a cluster-like flower structure to reduce the energy consumption of Fenton reaction. The characterization results revealed that the simultaneous lattice doping of ZnO by Cu and S successfully induced the surface polarization distribution of free electrons, forming electron-rich/poor microregions over CS/ZO NSs. The CS/ZO NSs/H2O2 system showed excellent performance for refractory pollutant removal including ciprofloxacin, with a removal efficiency of 99.2% in 60 min, and achieved rapid and efficient removal of refractory organic matters and natural organic matter in wastewater in 120 min. Dissolved oxygen can act as an electron acceptor to gain electrons directly on the catalyst surface to be activated to superoxide radicals (HO2•/O2•–) without external energy input in CS/ZO NSs suspension. Just trace hydrogen peroxide (H2O2) can stimulate the electron-donation effect from pollutants to the electron-deficient microregions. H2O2 can also be reduced to hydroxyl radicals (•OH) in the electron-rich microregions to destroy the contaminants. The synergistic linkage of the surface electron-poor and electron-rich microregions achieves excellent purification performance with a high efficiency and low energy.