Abstract
Shape effects of nanocrystal catalysts in different reactions have attracted remarkable attention. In the present work, three types of alpha-Fe2O3 oxides with different micromorphologies were rationally synthesized via a facile solvothermal method and adopted in deep oxidation of ethane. The physicochemical properties of prepared materials were characterized by XRD, N-2 sorption, FE-SEM, HR-TEM, FTIR, in situ DRIFTS, XPS, Mossbauer spectroscopy, in situ Raman, electron energy loss spectroscopy, and H-2-TPR. Moreover, the formation energy of oxygen vacancy and surface electronic structure on various crystal faces of alpha-Fe2O3 were explored by DFT calculations. It is shown that nanosphere-like alpha-Fe2O3 exhibits much higher ethane destruction activity and reaction stability than nanocube-like alpha-Fe2O3 and nanorod-like alpha-Fe2O3 due to larger amounts of oxygen vacancies and lattice defects, which greatly enhance the concentration of reactive oxygen species, oxygen transfer speed, and material redox property. In addition to this, DFT results reveal that nanosphere-like alpha-Fe2O3 has the lowest formation energy of oxygen vacancy on the (110) facet (E-vo (110) = 1.97 eV) and the strongest adsorption energy for ethane (-0.26 eV) and O-2 (-1.58 eV), which can accelerate the ethane oxidation process. This study has deepened the understanding of the face dependent activities of alpha-Fe2O3 in alkane destruction.