Crystal Phase‐Dependent Performance of RuO <sub>x</sub> /MnO <sub>2</sub> Nanorods for Alkaline Oxygen Evolution Reaction
Tingting Pan, Wei‐Hsiang Huang, Hongyuan Jie, Min‐Hsin Yeh, Kangshu Li, Meixin Chen, Xiaoyan Zhou, Jingjie Ge, Xuning Li, Xiaoxu Zhao, Zhiwei Hu, Yipu Liu, Jiwei Ma, Hongfei Cheng
Abstract
Abstract MnO 2 is a widely studied non‐noble metal electrocatalyst for the oxygen evolution reaction (OER) and has demonstrated phase‐dependent performance. Among the various MnO 2 polymorphs, γ‐MnO 2 has abundant defects and vacancies due to its disordered crystal structure of both β‐MnO 2 and R‐MnO 2 intergrowth, thus being a potential high‐performance OER catalyst. However, γ‐MnO 2 has been studied much less than other crystal phases of MnO 2 , and γ‐MnO 2 ‐based heterostructures are rarely reported. In this study, it is discovered that γ‐phase plays a unique role in RuO x /MnO 2 heterostructured nanorods. Among the pristine α‐, β‐, and γ‐MnO 2 polymorphs, α‐phase shows the best OER activity; however, after loading RuO x nanoclusters, RuO x /γ‐MnO 2 shows the largest enhancement and hence the best OER activity with an overpotential of 255 mV at 10 mA cm −2 and excellent stability (> 300 h), which is much superior to the commercial RuO 2 catalyst. Furthermore, when tested in an anion exchange membrane water electrolyzer (AEMWE), it maintains excellent durability at 200 mA cm −2 over 380 h. Mechanistic study shows that RuO x /γ‐MnO 2 exhibits the strongest electron transfer between Ru and Mn, which significantly weakens the Mn‐O bond strength and reduces the interaction between intermediates and the MnO 2 surface, ultimately resulting in the lowest energy barrier for the reaction.