Stable cuprous active sites in Cu+-graphitic carbon nitride: Structure analysis and performance in Fenton-like reactions.

Cu+-based catalysts have great potential in Fenton reactions under neutral pH conditions. However, cuprous (Cu+) materials are instable in the aqueous environment. Herein, using the cheap precursors, a Cu+-graphitic carbon nitride complex with an efficient Fenton-like activity as well as relative stability was prepared. 99.2% removal of Rhodamine B with an initial concentration of 50 mg/L could be attained in 1 h. Several experimental techniques are employed to study the structure of this catalyst. Results show that after the addition of Cu, the graphitic carbon nitride (g-C3N4) network is partially destroyed and the reduced Cu is therefore firmly embedded in the fragmentary g-C3N4 sheet. The X-ray adsorption fine spectra illustrates the chemical state and the local structure of the bonded Cu. Due to the strong orbital hybridization, Cu+ could be stabilized through the coordination with pyridinic N. A two-coordinate structure with a bond length of 1.90 Å is confirmed and this structure is not changed even after the Fenton-like reaction. Singlet oxygen (1O2) and hydroxyl radicals (HO•) are produced by the rapid interaction of bonded Cu+ with H2O2 and the resulting Cu2+ can be easily reduced to its cuprous state due to its structure stability, leading to its high activity in the Fenton-like reaction.