Revealing the active species of Cu-based catalysts for heterogeneous Fenton reaction

[Display omitted] •Cu species could be rationally tuned via reducing Cu@SiO2 catalysts properly.•The Cu+ dominating catalyst showed remarkably high degradation performance.•Cu+ species are the main active sites for the generation of ·OH.•DFT corroborated the Cu+ acting as the most active species for H2O2 activation. Cu-based heterogeneous Fenton catalysts are promising for industrial wastewater treatment, nevertheless it remains a great challenge to understand the catalytic mechanism due to the difficulty in identifying the critical roles of coexisting Cu0, Cu+ and Cu2+ species in the technical catalysts. In order to identify the catalytic roles of various copper species, core-shell Cu@SiO2 catalysts reduced at different reduction temperatures were studied for rhodamine B degradation. The Cu+ dominating catalyst, Cu@SiO2-R200, exhibited the highest degradation rate with more than 95% RhB (10 ppm) removal within 10 min. Combined with multiple techniques, including in situ spectroscopy, and density functional theory calculations, it can be concluded that Cu+ acts as the primary active species with the highest efficiency in activating the H2O2 to produce ·OH and subsequently degrading the contaminants. In this work, the structure-performance relationship of Cu-based heterogeneous Fenton reaction was elucidated to inspire the rational design of high-performance heterogeneous catalysts.