Improving Electrocatalytic Oxygen Evolution through Local Field Distortion in Mg/Fe Dual‐site Catalysts
Jing Zhang, Yufeng Zhao, Wanting Zhao, Jing Wang, Yongfeng Hu, Chengyu Huang, Xingli Zou, Yang Liu, Dengsong Zhang, Xionggang Lu, Hong Jin Fan, Yanglong Hou
Abstract
Abstract Transition metal single atom electrocatalysts (SACs) with metal‐nitrogen‐carbon (M−N−C) configuration show great potential in oxygen evolution reaction (OER), whereby the spin‐dependent electrons must be allowed to transfer along reactants (OH − /H 2 O, singlet spin state) and products (O 2 , triplet spin state). Therefore, it is imperative to modulate the spin configuration in M−N−C to enhance the spin‐sensitive OER energetics, which however remains a significant challenge. Herein, we report a local field distortion induced intermediate to low spin transition by introducing a main‐group element (Mg) into the Fe−N−C architecture, and decode the underlying origin of the enhanced OER activity. We unveil that, the large ionic radii mismatch between Mg 2+ and Fe 2+ can cause a FeN 4 in‐plane square local field deformation, which triggers a favorable spin transition of Fe 2+ from intermediate (d xy 2 d xz 2 d yz 1 d z2 1 , 2.96 μ B ) to low spin (d xy 2 d xz 2 d yz 2 , 0.95 μ B ), and consequently regulate the thermodyna‐mics of the elementary step with desired Gibbs free energies. The as‐obtained Mg/Fe dual‐site catalyst demonstrates a superior OER activity with an overpotential of 224 mV at 10 mA cm −2 and an electrolysis voltage of only 1.542 V at 10 mA cm −2 in the overall water splitting, which outperforms those of the state‐of‐the‐art transition metal SACs.