Flexibility Tuning of Dual‐Metal S─Fe─Co─N<sub>5</sub> Catalysts with O‐Axial Ligand Structure for Electrocatalytic Water Splitting
Hui Su, Shaojia Song, Ning Li, Yangqin Gao, Peng Li, Lei Ge, Tianyi Ma
Abstract
Abstract The electrocatalytic performance of metal–nitrogen–carbon (M─N─C) single‐atom catalysts remains a significant challenge due to their rigid active center. Controllable tuning of the local microenvironment and electronic structure is critical for M─N─C single‐metal site catalysts in improving the electrochemical performance and exploring the reaction mechanism. Herein, Co─N 4 is selected as a benchmark among various M─N─C catalysts based on theoretical prediction and experimental studies. A dual‐metal S─Fe─Co─N 5 catalyst is constructed by embedding Fe and S into the structure of Co─N 4 motifs. Theoretical analysis and in situ characterizations illustrate that the active sites will in situ combine an O‐axial ligand to form S─Fe─Co─N 5 ─O structure during the oxygen evolution reaction (OER), which can reduce the reaction energy of O * →OOH * . The Ab Initio Molecular Dynamics simulations and deformation energy for H * /O * adsorption reveal that the Fe─Co and S─Fe bonds exhibit flexible characteristics compared to the Co/Fe─N bonds. This flexibility of S─Fe─Co─N 5 ─O structure facilitates the OER performance by reducing the OOH * →O 2 , which is the OER rate‐determining step, resulting in superior performance. The optimized S─Fe─Co─N 5 ─O catalyst exhibits excellent OER (260 mV@50 mA cm −2 ) and hydrogen evolution reaction (138 mV@10 mA cm −2 ) performance in alkaline electrolytes. The reported regulation strategy ameliorates the micro‐environment of Co─N 4 with tunable flexibility, which helps allow a basic comprehension of the electrochemical reaction mechanism.