Mn‐Based Mullites for Environmental and Energy Applications

Abstract Mn‐based mullite oxides AMn 2 O 5 (A = lanthanide, Y, Bi) is a novel type of ternary catalyst in terms of their electronic and geometric structures. The coexistence of pyramid Mn 3+ –O and octahedral Mn 4+ –O makes the d‐orbital selectively active toward various catalytic reactions. The alternative edge‐ and corner‐sharing stacking configuration constructs the confined active sites and abundant active oxygen species. As a result, they tend to show superior catalytic behaviors and thus gain great attention in environmental treatment and energy conversion and storage. In environmental applications, Mn‐based mullites have been demonstrated to be highly active toward low‐temperature oxidization of CO, NO, volatile organic compounds (VOCs), etc. Recent research further shows that mullites decompose O 3 and ozonize VOCs from −20 °C to room temperature. Moreover, mullites enhance oxygen reduction reactions (ORR) and sulfur reduction reactions (SRR), critical kinetic steps in air‐battery and Li–S batteries, respectively. Their distinctive structures also facilitate applications in gas‐sensitive sensing, ionic conduction, high mobility dielectrics, oxygen storage, piezoelectricity, dehydration, H 2 O 2 decomposition, and beyond. A comprehensive review from basic physicochemical properties to application certainly not only gains a full picture of mullite oxides but also provides new insights into designing heterogeneous catalysts.