The effect of cobalt ions doping in ZnCr 2 O 4 spinel oxide for the catalytic activity of methane combustion

A series of novel cobalt ion-doped ZnCr 2− x Co x O 4 ( x = 0, 0.1, 0.15, 0.2) spinel oxides were synthesized with the hydrothermal method. X-ray diffraction, scanning electron microscope, specific surface area, Raman spectroscopy, X-ray photoelectron spectroscopy, temperature-programmed desorption of oxygen, and other analytical techniques were used to characterize the structure, morphology, and catalytic performance of each sample. Experiment results showed that the doping of cobalt ion significantly promoted the phase crystallization of spinel oxide. Cobalt ion-doped ZnCr 2− x Co x O 4 ( x = 0.1, 0.15, 0.2) nanoparticles with high specific surface area were synthesized at 773 K, with ZnCr 2 O 4 forming a spinel phase at 1173 K. Catalytic experiments revealed that the catalytic activity of ZnCr 2− x Co x O 4 was effectively improved. Cobalt ion-doped ZnCr 1.85 Co 0.15 O 4 catalyst catalyzed methane combustion reaction temperature at T 90% (the temperature where 90% of methane was converted) of about 573 K, while the undoped ZnCr 2 O 4 sample had the highest catalytic performance at T 90% of about 773 K. The order of catalytic activity was: ZnCr 1.85 Co 0.15 O 4 > ZnCr 1.9 Co 0.1 O 4 > ZnCr 1.8 Co 0.2 O 4 > ZnCr 2 O 4 . Results of catalytic experiments showed that the surface area of the catalyst increased after partial replacement of chromium ions by cobalt ions and that the increase in surface area of the catalyst provided more active sites, thus improving the reaction activity.