Effect of partial substitution of Zn2+ with Co2+ on catalytic methane combustion performance of Zn1-xCoxGa2O4 (x=0, 0.1, 0.3) microspheres

The modified ZnGa 2 O 4 microspheres were prepared by the conventional hydrothermal method and used to catalyze methane combustion reaction. Because Co 2+ and Zn 2+ have similar ion radii, so it seems that the Zn 2+ at the tetrahedral (T d ) position of ZnGa 2 O 4 was partially replaced by Co 2+ to adjust the oxygen distribution, and finally the Zn 1-x Co x Ga 2 O 4 (x = 0.1, 0.3) microspheres catalysts was obtained. X-ray photoelectron spectroscopy (XPS) analysis exhibited that Co 3+ were present in the Zn 1-x Co x Ga 2 O 4 (0.1, 0.3) samples, and interstitial oxygen were formed to maintain electrical neutrality. Oxygen temperature programmed desorption (O 2 -TPD) profiles showed that there was only one oxygen species desorption from ZnGa 2 O 4 sample, while the Zn 1-x Co x Ga 2 O 4 (0.1, 0.3) samples had two oxygen desorption peaks, that is the first one is surface adsorbed oxygen, the second is lattice oxygen. The catalytic methane combustion performance of the samples indicated that the partial substitution of Co 2+ for Zn 2+ in ZnGa 2 O 4 can effectively improve its activity.