Engineering Oxygen Vacancies of Co-Mn-Ni-Fe-Al High-Entropy Spinel Oxides by Adjusting Co Content for Enhanced Catalytic Combustion of Propane

초록

Transition metal-based oxides with similar oxidation activities for catalytic hydrocarbon combustion have attracted much attention. In this study, a new class of metal high-entropy oxides (CoxMnNiFeAl)(3)O-4 (x = 1, 2, 3, 4, 5) with a porous structure was fabricated through a simple and inexpensive NaCl template-assisted sol-gel approach, which was employed for the catalytic oxidation of propane. The results indicated that the content of cobalt has a great impact on its activity, and the (Co4MnNiFeAl)(3)O-4 catalyst exhibited the best catalytic activity. At the high space velocity of 60 000 mL<middle dot>g(-1)<middle dot>h(-1), the optimized one with high-temperature treatment can still achieve 90% propane conversion at 309 degrees C, which is 68 and 178 degrees C lower than those of the (CoMnNiFeAl)(3)O-4 catalyst and pure cobalt oxide, respectively. Meanwhile, it has the lowest apparent activation energy (46.6 KJ<middle dot>mol(-1)) and the fastest reaction rate (26.976 x 10(-6) mol<middle dot>g(cat)(-1)<middle dot>s(-1) at 290 degrees C). The improved performance of the (Co4MnNiFeAl)(3)O-4 catalyst could be attributed to the enhancement of low-temperature reducibility, the increased number of reactive surface oxygen species, and the cocktail effect of the high-entropy oxides. This work provides new insights into the preparation of efficient light alkane degradation catalysts and a realistic approach for the large-scale application of high-entropy oxides in the field of oxidation catalysts.

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