Insights into key parameters of MnO2 catalyst toward high catalytic combustion performance

Controllable crystal phases (α-, β-, γ- and δ-) of MnO2 materials were developed via tuning hydrothermal conditions and investigated in toluene catalytic combustion. Extensive characterization techniques such as XRD, BET, SEM, TEM, H2-TPR and XPS were employed for analyzing the structure-performance relationship between physicochemical properties, such as specific surface area, vacancy/lattice oxygen and their mobility, reduction property and catalytic activity. Results indicated that the degradation activity of MnO2 catalyst greatly hinges on materials intrinsic properties, namely the vacancy oxygen generation, lattice oxygen content and their reduction behaviors. α-MnO2 exhibited the best catalytic activity (0.24 μmol/min @ 240 °C) among the obtained MnO2 materials; however, its cycle stability was inferior to that of δ-MnO2 catalyst owing to the different moderating effect of potassium ions remained within the tunnels or mezzanines structure. In addition, δ-MnO2 showed an easiest reduction property among all the manganese oxides investigated. The findings will shed lights on designing of Mn-based catalysts with a higher VOCs combustion capacity.