Balancing surface acidity, oxygen vacancies and Cu+ of CuOx/CeO2 catalysts by Nb doping for enhancing CO oxidation and moisture resistance and lowering byproducts in plasma catalysis

Abstract

The development of a non-noble metal catalyst is a challenging task in plasma catalysis to achieve high CO conversion and low amount of by-products (O3 and NOx) under low energy input and high humidity conditions. In this study, we have prepared several Nb-doped CuOx/CeNbOx catalysts with various Ce/Nb molar ratios. Among them, CuOx/Ce0.9Nb0.1Ox catalyst exhibited the highest CO conversion (>90%) and the lowest by-product emissions (O3 < 5 ppm; NOx < 20 ppm) at low energy density (~600 J/L) in plasma catalytic CO oxidation. Furthermore, it remained good stability under moisture-rich conditions (5.2% H2O). We employed XPS, UV-Raman, O2-TPD, NH3-TPD and in situ DRIFTS to elucidate the origin of enhancement effects. It was found that the appropriate amount of niobium doping well balanced the relationship among Cu+, oxygen vacancies and surface acidity, and inhibited the competitive adsorption of H2O. The findings can provide an avenue to solve the problems of incomplete oxidation and by-product emissions in the application of plasma technology.