MnO 2 ‐Mediated Synthesis of Mn 3 O 4 @CaMn 7 O 12 Core@Shell Nanorods for Electrocatalytic Oxygen Reduction Reaction

The rational design of low‐cost and earth‐abundant perovskite oxide alternatives as highly efficient and robust electrocatalysts for the oxygen reduction reaction (ORR) is desirable but remains a great challenge. Herein, we developed a simple MnO 2 ‐mediated synthetic approach to Mn 3 O 4 @CaMn 7 O 12 core@shell nanorods by impregnating MnO 2 nanorods with a certain amount of Ca(NO 3 ) 2 solution (Mn : Ca=15 : 1), followed by a calcination process at 850 °C in air. By adjusting the Mn : Ca molar ratios, Ca−Mn oxides with different structures can also be prepared. Benefiting from the intrinsic characteristics of CaMn 7 O 12 perovskite oxides and the structural advantage of nanorods, Mn 3 O 4 @CaMn 7 O 12 core@shell nanorods exhibit high ORR activity with a positive onset potential of 0.90 V and half‐wave potential of 0.75 V. Also, they have an excellent tolerance ability to methanol. More importantly, the work may pave a new avenue to design other novel electrocatalysts with high performance and stability towards energy conversion and storage applications.