Investigation of the Performance and Deactivation Mechanism of NO Removal by Photocatalysis of High-Entropy Oxides (BiCoNiCuMn)Ox

High entropy oxides (HEOs) have excellent light absorption performance, abundant active sites, and good photocatalytic stability, but there is currently little research on their photocatalytic activity for NOx. This work prepared (BiCoNiCuMn)Ox by a two-step solid-state grinding and high-temperature calcination method, and its photocatalytic NO removal efficiency reached 55%. However, the catalyst is significantly deactivated during the cyclic reaction process. In order to further investigate the deactivation mechanism, a series of comprehensive characterization techniques were employed in this study, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT). The research results indicate that the nitrate (NO3–) generated during the reaction process is the main factor leading to the deactivation of (BiCoNiCuMn)Ox. The accumulation of nitrate ions (NO3–) on the surface of the catalyst leads to the formation of an insulating layer, which hinders the performance of the catalyst. This study not only provides important insights into the deactivation mechanism of the (BiCoNiCuMn)Ox photocatalyst, but also establishes a theoretical framework for the practical application of high entropy oxides in environmental remediation.