Highly dispersed CuO_x decorated ZnO photocatalyst for low-concentration methane removal

Methane is a potent greenhouse gas, contributing 30 % of global warming. Herein, we report a low cost but efficient CuO_x/ZnO nanocomposite photocatalyst for total oxidation of methane into carbon dioxide under ambient conditions. The results show that the addition of a small amount (0.05 wt%) of CuO_x enhances the methane photo-oxidation activity of ZnO by about 7-fold. More importantly, the CuO_x/ZnO demonstrates good durability evidenced by steady performance after multiple cycles or after long-term storage. The promising performance of CuO_x/ZnO is attributed to two facts, i) highly dispersed CuO_x on the ZnO surface (indicated by N₂O selective oxidation experiments and X-ray absorption fine structure (XAFS)); ii) enhanced methane adsorption and carbon dioxide desorption on CuO_x/ZnO surface. The photocatalytic reaction mechanism of methane on CuO_x/ZnO was also investigated by in situ Fourier transform infrared spectroscopy (FTIR) and density functional theory (DFT) calculations. The results show that the highly dispersed Cu atoms on the ZnO surface favor the continuous oxidation of *OCH₃. The potential value of our work lies in its capacity to mitigate or even eliminate the greenhouse effect.