Preparation of hollow nanospheres g-C3N4 loaded by Keggin type Cu mono-substituted heteropoly acid with enhanced visible-light harvesting and electron transfer properties for high-efficiency photocatalysis

A series of heterojunction catalysts (CuCN-X) were successfully fabricated by loading the different amounts of Keggin type Cu mono-substituted heteropoly acid (HPW11Cu) on the surface of hollow nanospheres g-C3N4 (HSCN). The HSCNs were prepared by using SiO2 as a hard template. The chemical structure, porosity, morphology and electronic property of the prepared catalysts were investigated using XRD, SEM, N-2-absorption isotherm and XPS. The results indicated that the modified HSCN show prominent absorption in the visible light range and decrease the band gap. The greatly enhanced photocatalytic activity of obtained CuCN-X have been shown by the degradation of Rhodamine B (RhB), reduction of CO2 and production of photocatalytic hydrogen under visible light irradiation. More significantly, CuCN-15 has shown significantly improved photocatalytic performance at 4.5, 3.5 and 3.3 times higher that of than HSCN for the degradation of RhB, reduction of CO2 and production of photocatalytic hydrogen, respectively. Furthermore, the mechanism for the enhanced photocatalytic activity of CuCN-X is proposed to be due to the formation of heterojunction. The electrons can be rapidly transferred from HSCN to HPW11Cu, in which facilitate charge separation and charge transfer.