Catalytic oxidation mechanism of AsH₃ over CuO@SiO₂ core-shell catalysts via experimental and theoretical studies

In this study, CuO@SiO₂ core-shell catalysts were successfully synthesized and applied to efficiently remove hazardous gaseous pollutant arsine (AsH₃) by catalytic oxidation under low-temperature and low-oxygen conditions for the first time. In typical experiments, the CuO@SiO₂ catalysts showed excellent AsH₃ removal activity and stability under low-temperature and low-oxygen conditions. The duration of the AsH₃ conversion rate above 90 % for the CuO@SiO₂ catalysts was 39 h, which was markedly higher than that of other catalysts previously reported in the literature. The considerable catalytic activity and stability were attributed to the protection and confinement effects of the SiO₂ shell, which resulted in highly dispersed CuO nanoparticles. Meanwhile, the strong interaction between the CuO core and SiO₂ shell further facilitated the formation of active species such as coordinatively unsaturated Cu²⁺ and chemisorbed oxygen. The accumulation of oxidation products (As₂O₃ and As₂O₅) on the interface between the CuO core and SiO₂ shell and the pore channels of the SiO₂ shell is the main cause of catalysts deactivation. Furthermore, through combined density functional theory (DFT) calculations and characterization methods, a reaction pathway including gradual dehydrogenation (AsH₃*→AsH₂*→AsH*→As*) and gradual oxidation (2As*→As*+AsO*→2AsO*→As₂O₃) for the catalytic oxidation of AsH₃ on CuO (111) surface was constructed to clarify the detailed reaction mechanism. The CuO@SiO₂ core-shell catalysts applied in this study could provide a powerful method for developing AsH₃ catalysts from multiple know AsH₃ removal systems.