Dynamic Fe─F Coordination Triggered Structure-Adaptive Fe-N-C for Efficient Oxygen Reduction Electrocatalysis.

The sustainable and widespread developments of fuel cells require material innovation toward the sluggish oxygen reduction reaction (ORR). Although iron and nitrogen co-doped carbon material (Fe-N-C) is a promising alternative to scarce and expensive platinum-based electrocatalysts, the linear scaling relationships among the intermediates' adsorption energy limit maximum performance. Herein, we propose a coordination-adaptive catalyst design to bypass the intrinsic scaling relations through incorporating quasi-covalent Fe─F bond. Operando experiments and theoretical calculations demonstrate that the cleavage of Fe-F bond facilitates the activation of O and the formation of OOH*, while the self-healing of Fe─F bond regulates the binding strength with O* and OH*, thus breaking the OH*-OOH*/O* scaling relations. As a result, the well-designed F-Fe-N-C delivers a half-wave potential (E) of 0.91 V (versus RHE), along with significantly improved stability with only 2 mV loss in E after 80,000 voltage cycles. When applied to the cathode of anion-exchange membrane fuel cell, F-Fe-N-C exhibits high peak power density of 813 mW cm under H-air condition and achieves extremely high current (141 mA cm at 0.9 V) in H-O condition. This work not only offers a promising ORR electrocatalyst but also provides a new strategy to circumvent the fundamental constraint-linear scaling relationships.