One-step solution combustion synthesis of micro-nano-scale porous Cu/CeO2 with enhanced photocatalytic properties

Abstract

The Cu/CeO2 nanoporous composite material was prepared via a one-step and energy-saving method of solution combustion synthesis (SCS). The phase composition, surface morphology and optical characteristics of Cu/CeO2 were studied. The results show that the SCS products are composed of cubic fluorite CeO2 and Cu. Due to the generation and escape of gas during the synthetic reaction, the SCS CeO2 shows porous structure, in which the mesopores (diameter 10–17 nm) nest in the wall of large pores (diameter 80–300 nm). X-ray photoelectron spectroscopy (XPS) outcomes indicate that the oxygen vacancy concentration of CeO2 increases (18.97%–30.93%) with the increase of Cu concentration. The decoration of Cu greatly enhances the catalytic activity of CeO2 nanomaterials. 30 wt% Cu/CeO2 composite material shows the best photocatalytic activities for the degradation of methyl orange (MO) (95.99%), which is about 4.3 times that of CeO2 at the same time (120 min). UV-vis diffuse reflectance spectroscopy (DRS) results show that the semiconductor band gap is reduced with the addition of metallic Cu, which leads to the enhancement of photocatalytic activity. The free radical trapping experiments demonstrate that ·O2– and h+ are the main active species in the photocatalytic degradation of MO. Based on the above results, a hypothesized mechanism for enhanced photocatalysis of Cu/CeO2 nanomaterials was proposed: the porous structure provides more reactive sites and channels for mass transfer, and the presence of metallic Cu improves the oxygen vacancy concentration of CeO2 and then promotes charge-carrier separation, which helps enhance the photocatalytic performance of Cu/CeO2.