Copper deposition on MgO surfaces: Synergistic effect of multivalent Cu and oxygen vacancies efficiently activates H2O2 and enhances photo-Fenton efficiency

As a green solution for environmental cleanup, the technology of photocatalysis still suffers from insufficient light absorption and rapid electron-hole recombination. In this study, the copper was deposited on MgO surface by a UV-assisted photodeposition method. It was found that the deposition of copper introduced oxygen vacancies, improved photogenerated charge carrier separation, and enhanced visible light absorption. These improvements were also attributed to the formation of a Schottky barrier and the localized surface plasmon resonance (LSPR) effect of copper species. The synergistic effects of multivalent copper species (Cu 0 , Cu + , Cu 2+ , and Cu 3+ ) and the oxygen vacancies introduced by the deposition of copper significantly promoted the generation of reactive oxygen species (·O 2 ⁻), thereby accelerating the degradation process and enhance the photocatalytic degradation activity toward Rhodamine B (RhB). The 3 %Cu-MgO exhibited the highest photocatalytic efficiency, degrading 92.8 % of RhB within 60 min. The corresponding pseudo-first-order reaction rate constant was 0.04359 min⁻ 1 , approximately twice that of pristine MgO. Notably, 3 %Cu-MgO demonstrated excellent photocatalytic performance over a broad pH range (3.6–10) and maintained good cyclic stability. The study clarifies the multifaceted function of valence-variable copper species in the photo-Fenton process and provides a meaningful reference for the design and exploration of other multivalent metal-based photo-Fenton catalysts in future studies.