Copper Ion-Modified δ-MnO2 as an Efficient Catalyst for CO Oxidation

Carbon monoxide (CO) is a highly toxic, colorless, and odorless gas posing significant risks to human health and the environment. Catalytic oxidation offers a promising, economically viable solution by converting CO into nontoxic CO2 under mild conditions without energy-intensive regeneration. However, existing MnO2-based catalysts often exhibit poor activity and stability in harsh environments, particularly at low temperatures and high humidity. In this study, we propose a Cu2+ ion-exchange modification strategy to activate lattice oxygen species in δ-MnO2, thereby significantly enhancing its low-temperature CO oxidation performance. Structural characterization by XRD and SEM confirms that Cu-doped δ-MnO2 retains its original birnessite-type structure and porous morphology. ICP-OES and XPS analyses verify that Cu2+ ions effectively replace interlayer K+ ions. The resulting MnO2-150Cu catalyst demonstrates exceptional activity, achieving 100% CO conversion at 40 °C in dry air and maintaining full conversion at 80 °C in the presence of 1.3 vol.% H2O at a weight hourly space velocity of 150 L/g·h. H2-TPR and O2-TPD results confirm that Cu doping enhances the reducibility and mobility of lattice oxygen. Furthermore, in situ DRIFTS analysis reveals that the migration of active oxygen species is the rate-limiting step at low temperatures. This work provides a novel and effective strategy for activating lattice oxygen in MnO2-based catalysts, offering a promising pathway for developing high-performance materials for low-temperature CO oxidation under practical environmental conditions.