Single-Atom Ni Anchored on α-MnO<sub>2</sub> Nanorods as an Electrocatalyst for the Oxygen Evolution and Oxygen Reduction Reactions
Jianan Xie, Yilong Chen, Zhanglong He, Shan Liu, Yuling Liu, Bin Li, Tianjian Xu, Xiaohui Ning, Shuguang Chen, Taotao Zeng, Hao He
Abstract
Developing efficient MnO 2 -based bifunctional catalysts is a considerable challenge due to slow oxygen reduction reaction (ORR) kinetics and the limited activity of the oxygen evolution reaction (OER). Herein, an efficient bifunctional catalyst Ni/α-MnO 2 is prepared by a straightforward solid-phase synthesis method, enabling the anchoring of Ni atoms onto the α-MnO 2 surface. The electrochemically active surface area is significantly enhanced due to the generation of oxygen vacancies and presence of atomic Ni sites. After Ni decoration, the half-wave potential of the ORR is elevated to 0.82 V, while the overpotential for the OER is reduced to 366 mV, resulting in an exceptionally low overall oxygen overpotential (Δ E = 0.79 V). Density functional theory calculations reveal that the d-band center of Mn exhibits negative shifts, consequently lowering the energy barrier for the conversion of OOH* to O* in the ORR and that of OH* to O* in the OER. In a secondary zinc–air battery, a supreme power density of 290 mW cm –2 is acquired at a current density of 350 mA cm –2, surpassing the performance of pristine α-MnO 2 . This work offers valuable guidance for the development of high-performance MnO 2 -based bifunctional catalysts.