Enhanced moisture resistance of Cu/Ce catalysts for CO oxidation via Plasma-Catalyst interactions

Copper/cerium bimetallic catalyst is an efficient material for the removal of carbon monoxide, while the rapid deactivation under moisture-rich conditions in the conventional thermal-catalysis limited its wide application. Here, we investigated the plasma-assisted catalytic oxidation of CO over Cu/Ce oxides supported on γ-Alumina in comparison with the conventional thermal catalytic oxidation. The TOF values of the Cu/Ce catalysts showed that the plasma catalysis was the better catalytic system for CO oxidation (2.96 s^-1 for thermal catalysis, 5.13 s^-1 for plasma catalysis). Importantly, the energy barriers for plasma catalysis were much lower than that for thermal catalysis, especially under moisture-rich conditions (e.g. 130.3 kJ/mol versus 246.1 kJ/mol under 9.8 vol% water vapor). The loss of activity caused by water was reversible for the plasma process, but not for the thermal process. The Cu/Ce catalyst remained good stability within 60 h in the presence of 6.1% water for plasma oxidation, while the thermal catalytic activity declines gradually. Also, water could inhibit the formation of gas byproducts (O₃ and NO_x). The promoting role of plasma could be mainly ascribed to the enhanced strength of oxygen mobility and plasma-assisted decomposition of surface carbonate in the presence of water, as revealed by the in-situ NTP-TPR, XPS, and the ex-situ DRIFTS analyses.