Amorphous Nanoparticle Mullite With Tunable Surface Oxygen Deficiency For Enhanced Oxygen Electrocatalysis

The key technology of renewable energy transformation and storage include fuel cells,rechargeable metal air batteries,water splitting,etc.And the core problem for us is to develop efficient and cheap ORR and OER catalysts based on non-noble elements instead of the high cost,scarcity,insufficient durability commercial Pt/C and RuO₂catalysts.Manganese-based oxides have exhibited high promise as non-coinage alternatives to Pt/C for catalyzing oxygen reduction reaction?ORR?in basic solution and a mix of Mn^3+/4+valence is believed to be vital in achieving optimum ORR performance.Here,we propose that,distinct from the most studied perovskites and spinels,Mn-based mullites with equivalent molar ratio of Mn³⁺and Mn⁴⁺provide a unique platform to maximize the role of Mn valence in facile ORR kinetics by introducing modest content of oxygen deficiency,which is also beneficial to enhanced catalytic activity.Accordingly,amorphous mullite SmMn₂O_5-?nanoparticles with finely tuned concentration of oxygen vacancies are synthesized via a versatile top-down approach and the modest oxygen-defective sample with Mn³⁺/Mn⁴⁺ratio of 1.78,i.e.,Mn valence of 3.36,gives rise to a superior overall ORR activity among the highest reported for the family of Mn-based oxides,comparable to that of Pt/C.Altogether,our study opens up great opportunities for mullite-based catalysts to be a cost-effective alternative to Pt/C in diverse electrochemical energy storage and conversion systems.