Flexibility Tuning of Dual‐Metal S─Fe─Co─N5 Catalysts with O‐Axial Ligand Structure for Electrocatalytic Water Splitting

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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─N4 is selected as a benchmark among various M─N─C catalysts based on theoretical prediction and experimental studies. A dual‐metal S─Fe─Co─N5 catalyst is constructed by embedding Fe and S into the structure of Co─N4 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─N5─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─N5─O structure facilitates the OER performance by reducing the OOH*→O2, which is the OER rate‐determining step, resulting in superior performance. The optimized S─Fe─Co─N5─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─N4 with tunable flexibility, which helps allow a basic comprehension of the electrochemical reaction mechanism.
Funding Information
  • National Key Research and Development Program of China (2021YFA1501300, 2019YFC1907602)
  • National Natural Science Foundation of China (51572295, 21273285, 21003157)
  • Australian Research Council (FT210100298, FT210100806, DP220100603, LP210100467, LP210200504, LP210200345, LP220100088)
  • Australian Government

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