Enhanced Catalytic Performance of MnO2 Nanowires for Soot Combustion by Cobalt Incorporation

Abstract

The impact of Cobalt (Co) doping on the structure, redox, and catalytic properties of MnO₂ nanowires (NWs) for soot combustion was investigated. XRD analysis revealed that pure MnO₂ NWs exhibit a mixture of major α-MnO₂ and minor γ-MnO₂ phases, while Co doping at 10 mol% enhanced the γ-MnO₂ content and induced unbalanced charge in the MnO₂ structure via Mn substitution by Co, which induced lattice defects, including oxygen vacancies. SEM images confirmed the successful formation of nanowire morphology using the hydrothermal method for all prepared catalysts. H₂-TPR profiles demonstrated enhanced reducibility and oxygen mobility in Co-doped catalysts, attributed to synergistic effects between Mn and Co species and increased oxygen vacancy concentration. The soot oxidation mechanism suggested that oxygen vacancies and mobility play a key role in sustaining lattice oxygen activation. Catalytic activity tests for soot combustion revealed that 10mol%Co-doped MnO₂ NWs achieved the lowest T₅₀ (363 ^οC), outperforming both pure MnO₂ NWs and 20mol%Co-doped MnO₂ NWs, due to optimized surface area, redox properties, and oxygen mobility. Post-reaction investigations demonstrated that the nanowire catalyst might provide sustained catalytic performance over several reaction cycles by converting to catalytically active Mn₃O₄ without morphological degradation.