Enhanced CO₂ hydrogenation performance of CoCrNiFeMn high entropy alloys

CO₂ hydrogenation is a promising process for removing anthropogenic CO₂ emissions and yielding C1 chemicals that can be utilized as fuels and valuable precursors for chemical synthesis. Commercial high-entropy alloys (HEAs) have widespread application in various fields owing to their exceptional thermal stability and tunable microstructure. However, their potential application as catalysts is often limited by the low exposure of active sites. In this study, the commercial CoCrNiFeMn powder was applied for atmospheric pressure CO₂ hydrogenation and enhanced its catalytic performance by a combined treatment of ball milling and high-temperature H₂ reduction. The high-energy ball milling results in a morphological transition in CoCrNiFeMn HEAs from spherical to irregular. This transformation leads to a significant decrease in particle size and more surface reactive sites. The high-temperature H₂ reduction promoted the atomic rearrangement on the CoCrNiFeMn surface, thereby improving its alloy structural homogeneity. These modifications greatly improve the performance of CoCrNiFeMn for CO₂ hydrogenation. This work introduces a facile modification approach to facilitate the catalytic efficiency of commercial HEAs in CO₂ hydrogenation with high selectivity.