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.