Heterogeneous catalysis triggered in the novel copper-palladium spinel oxides through electron delocalization and oxygen vacancies for efficient degradation of organic contaminants.

In Fenton-like reactions, enhancing the activation efficiency of peroxymonosulfate (PMS) is a critical factor for generating diverse reactive oxygen species, but improving PMS adsorption capacity and accelerating electron transfer remain major challenges to boost reaction kinetics. This study designed and synthesized a novel copper-palladium (Cu-Pd) bimetallic spinel oxide, where Pd doping into spinel-structured and layered copper oxides effectively generated a substantial number of oxygen vacancies and precisely regulated the electronic structure-two core factors that dominate PMS activation efficiency. A key finding of this work is that electron delocalization at highly active Cu-Pd sites, coupled with abundant oxygen vacancies, enables rapid PMS activation and significantly promotes the cycling efficiency of Pd2+/Pd0 and Cu2+/Cu+ at the catalyst interface. In the Cu2PdO3/PMS system, the degradation efficiency of bisphenol A (BPA) reached 100% within 5 min, with a corresponding rate constant of 0.501 s-1, which was 11.65 and 22.77 times higher than those of pure Pd oxide and Cu oxide, respectively. The integration of experimental characterization with density functional theory (DFT) calculations reveals that oxygen vacancies and electron transfer are the primary catalytic mechanisms: the pronounced electron delocalization at Cu/Pd sites facilitates the adsorption of ∗HSO5/∗OH intermediates on the "metal-Vo bridge" structure. This study provides a representative case and for spinel oxides-based PMS activation, offers novel insights into the regulatory roles of oxygen vacancies and electron delocalization, and lays critical references for the development of advanced environmental remediation catalysts.