Boosting ORR Activity via Bidirectional Regulation of the Electronic Structure by Coupling MnO/Mn<sub>3</sub>O<sub>4</sub> Composite Materials with N-Doped Carbon
Xiaowei Zhao, Mingwang Lu, Guanhua Zhang, Yuekun Hu, Yan Liu, Xiaojing Yang, Xiaofei Yu, Xinghua Zhang, Zunming Lu, Lanlan Li
Abstract
Suffering from poor conductivity and limited activity, manganese oxide was combined with carbon materials to promote electrocatalytic performance. Although the positive effects of the carbon composition strategy in performance promotion have been confirmed, the underlying mechanism involved remains unclear, which hinders the development of manganese oxide catalysts. Here, N-doped carbon (NC) shell-encapsulated MnO/Mn 3 O 4 composite nanoparticles grown on NC nanorods were designed to catalyze the oxygen reduction reaction. The resulting MnO/Mn 3 O 4 @NC has excellent activity ( E 1/2 = 0.853 V) and extraordinary durability, comparable to Pt/C. The MnO/Mn 3 O 4 composite achieved an optimal e g occupancy of Mn 3+ . The NC shell formed in situ offers the electron transfer from MnO/Mn 3 O 4 to the NC and results in bidirectional regulation of the electronic structure, forming electron-accumulated NC and Mn 3+ -rich manganese oxide systems. Electron accumulation on NC enhances the affinity for O 2 adsorption, thereby significantly reducing the free-energy barrier for the ORR process. Furthermore, the NC shell formed in situ improves the electric conductivity and cycle durability of catalysts significantly. This paper fundamentally reveals the crucial role of the coupling effect between MnO/Mn 3 O 4 and NC formed in situ in promoting catalysis and provides an efficient strategy for designing other metal oxide electrocatalysts.