Engineering Molecular Heterostructured Catalyst for Oxygen Reduction Reaction
Chang Chen, Chang Chen, Yifan Li, Aijian Huang, Xuerui Liu, Jiazhan Li, Yu Zhang, Zhiqiang Chen, Zewen Zhuang, Yue Wu, Weng‐Chon Cheong, Xin Tan, Kaian Sun, Zhiyuan Xu, Di Liu, Zhiguo Wang, Kebin Zhou, Chen Chen, Chen Chen
Abstract
Introducing a second metal species into atomically dispersed metal–nitrogen–carbon (M–N–C) catalysts to construct diatomic sites (DASs) is an effective strategy to elevate their activities and stabilities. However, the common pyrolysis-based method usually leads to substantial uncertainty for the formation of DASs, and the precise identification of the resulting DASs is also rather difficult. In this regard, we developed a two-step specific-adsorption strategy (pyrolysis-free) and constructed a DAS catalyst featuring FeCo “molecular heterostructures” (FeCo-MHs). In order to rule out the possibility of the two apparently neighboring (in the electron microscopy image) Fe/Co atoms being dispersed respectively on the top/bottom surfaces of the carbon support and thus forming “false” MHs, we conducted in situ rotation (by 8°, far above the critical angle of 5.3°) and directly identified the individual FeCo-MHs. The formation of FeCo-MHs could modulate the magnetic moments of the metal centers and increase the ratio of low-spin Fe(II)–N 4 moiety; thus the intrinsic activity could be optimized at the apex of the volcano-plot (a relationship as a function of magnetic moments of metal–phthalocyanine complexes and catalytic activities). The FeCo-MHs catalyst displays an exceptional ORR activity ( E 1/2 = 0.95 V) and could be used to construct high-performance cathodes for hydroxide exchange membrane fuel cells and zinc–air batteries.