Effects of the Morphology of MnO₂ Nanostructures on the Catalytic Oxidation of Toluene

ThreeMnO(2) samples with flower (F-MnO2),rod (R-MnO2), and tube (T-MnO2) morphologieswere constructed herein for catalytic toluene oxidation. T-MnO2 is superior to the other two in terms of catalytic performanceand water resistance stability for toluene combustion. Overall structuraland physicochemical properties characterized by X-ray diffraction,Raman spectroscopy, N-2 adsorption-desorption, H-2 temperature-programmed reduction, O-2 temperature-programmeddesorption, X-ray photoelectron spectroscopy, and toluene temperature-programmeddesorption verified that T-MnO2 exhibited larger specificsurface area, stronger reducibility, and more plentiful surface oxygenspecies than F-MnO2 and R-MnO2, which couldgreatly enhance the activation and mobility of oxygen species. Notably,in situ diffuse-reflectance infrared Fourier transform spectroscopywas conducted to investigate the relationship between the activityand surface oxygen species on these catalysts. It was found that thesurface lattice oxygen played an important role in the activation-oxidationprocess of toluene, and the difference in the surface oxygen specieson the catalysts led to obvious activity changes due to their differentmorphologies.