CuO-modified WO3 for stable photocatalytic NO oxidation: Overcoming photocorrosion and side reactions.

Tungsten trioxide (WO₃) is an attractive photocatalyst for visible light applications, but its practical use is hindered by its instability due to the easy photoreduction of W⁶⁺ to W⁵⁺. To enhance its stability and efficiency, we developed a novel heterojunction by preparing nanoscale CuO on WO₃ nanosheets via a one-step calcination method. This CuO/WO₃ heterojunction effectively inhibits photocorrosion through an S-scheme charge transfer mechanism that redirects electrons from WO₃ to CuO. The optimized heterojunction achieved a significantly enhanced NO removal efficiency of 62%, which is approximately 2.2 times higher than that of pure WO₃ (27%), while also exhibiting excellent stability during cycling tests. The presence of CuO not only stabilized the WO₃ by diverting the hot electrons from the WO3 surface, but also inhibited the production of toxic NO2 on WO3 through the singlet oxygen. This study demonstrates an effective strategy for constructing stable and efficient photocatalysts for atmospheric pollutant removal by optimizing interfacial charge transfer.