Positive effects of Al3+ partially substituted by Co2+ cations on the catalytic performance of Co1+x Al2−x O4 (x = 0–0.2) for methane combustion

Abstract

Co1+x Al2−x O4 (x = 0–0.2) catalysts were prepared by sol–gel method using citric acid as a chelating agent calcined at 1100 °C and then investigated for methane combustion. The catalytic activity of CoAl2O4 was significantly enhanced after Al3+ partially substituted by Co2+ cations in methane combustion. X-ray diffraction showed that all the Co1+x Al2−x O4 (x = 0–0.2) samples displayed a spinel-type single phase. Raman spectroscopy deduced that Al3+ partially substituted by Co2+ cations created structural defects and lattice distortion, which was indicated to be favorable for the formation of oxygen vacancy and weakening the bond strength of Al–O. X-ray photoelectron spectroscopy revealed that the excellent catalytic activity for methane combustion may be attributed to the active octahedral coordinated Co3+ cations and surface oxygen vacancies, especially the active octahedral coordinated Co3+ cations predominantly determined for methane combustion.