Engineering Grain Boundary and Surface Sites of Binary Cu-Mn Catalysts to Boost CO Oxidation

Abstract

The catalytic oxidation of CO over Cu-based catalysts has garnered significant interest due to their promising potential in addressing environmental pollution and enhancing industrial processes. Herein, we report a dual-stimuli strategy to boost the catalytic performance of CO oxidation via synergistically harnessing active Cu+ species with oxygen vacancies by engineering the grain boundary of Cu-Mn catalysts. The nanorod-like MnO2 with a tunnel structure was prepared by a hydrothermal method and employed as the catalyst support, where different amounts of Cu were further introduced via impregnation to obtain Cu/MnO2 catalysts. It is found that apart from the highly dispersed Cu species within MnO2 lattice to create lattice mismatch and distortion, some Cu are present as oxidized nanoparticles over MnO2 surface, thus sparking off increased dislocations and grain boundaries. A combination of characterizations demonstrates that the proportion of active Cu+ species decreases with the increasing amount of Cu, presenting an inverse relationship to the abundance of oxygen vacancies over catalyst surface. Correspondingly, both Cu+ species and oxygen vacancies are identified as the main active sites for the adsorption and activation of CO and O2, respectively. Therefore, a trade-off between the percentage of active Cu+ species and oxygen vacancies for the 15% Cu/MnO2 catalyst with a moderate Cu introduction contributes to its highest catalytic activity, with T50 and T90 reaching 66 °C and 89 °C, respectively. This investigation highlights the potential of synergistically harnessing active Cu+ species with oxygen vacancies via grain boundary engineering for enhanced catalytic performance in CO oxidation applications.