Improving CO Oxidation Catalysis Over High Entropy Spinels by Increasing Disorder.

Abstract

Enhancing the activity and stability of earth-abundant, heterogeneous catalysts remains a key challenge, requiring new materials design strategies to replace platinum-group metals. Herein, it is demonstrated that increasing the configurational disorder of spinel metal oxides (M₃O₄, where M is a combination of Cr, Mn, Fe, Co, Ni, Cu, and Zn) leads to significant improvements in carbon monoxide (CO) oxidation performance. A substantial 63% decrease in the T₁₀ value (temperature to reach 10% CO oxidation) is observed by systematically increasing the number of first-row transition metals within the spinel oxide. Long-term stability studies reveal that the most disordered 7-metal spinel oxide exhibited superior resistance to catalyst deactivation compared to the 4-metal variant, showing a decrease in activity of only 4.7% versus 12.2% during 14 h of operation. A solventless thermolysis approach is developed to synthesize a series of medium entropy spinel oxide (MESO) and high entropy spinel oxides (HESOs) from discrete, air-stable molecular precursors. Comprehensive crystal structure determination, elemental distribution analysis, and surface characterization are conducted, establishing a clear structure-function relationship between elemental composition, configurational disorder, and catalytic performance. This work highlights how configurational disorder can serve as an effective design principle for developing both active and stable catalysts.