A new popular transition metal-based catalyst: SmMn2O5 mullite-type oxide

Catalyst with high performance has drawn increasing attention recently due to its significant advantages in chemical reactions such as speeding up the reaction, lowering the reaction temperature or pressure, and proceeding without itself being consumed. Despite the superior catalytic performance of precious metal catalysts, transition metal oxides offer a promising route for substitution of precious metals in catalysis arising from their low cost, intrinsic activity and sufficient stability. Mullite-type oxide SmMn2O5 exhibits a unique crystal structure containing double crystalline fields, and nowadays is used widely as the catalyst in different chemical reactions, including the reactions of vehicle emissions reduction and oxygen evolution reaction, gas sensors, and metal-air batteries, promoting attention in catalytic performance enhancement. To our knowledge, there is no review article covering the comprehensive information of SmMn2O5 and its applications. Here we review the recent progress in understanding of the crystal structure of SmMn2O5 and its basic physical properties. We then summarize the catalytic sources of SmMn2O5 and reaction mechanisms, while the strategies to improve catalytic performance of SmMn2O5 are further presented. Finally, we provide a perspective on how to make further progress in catalytic applications.