Atomically dispersed iron–nitrogen (FeN₄) catalysts have emerged as the most promising alternative to costly Pt-based counterparts in proton exchange membrane fuel cells (PEMFCs), but often they suffer from high overpotential and poor stability due to the diverse iron–nitrogen coordination structure. Herein, we demonstrate high-purity pyrrole-type FeN₄ sites for the first time, as a superior ORR electrocatalyst for PEMFCs. The high-purity pyrrole-type FeN₄ catalyst exhibited extremely outstanding ORR activity with an ultra-high active area current density of 6.89 mA m⁻² in acid medium, which exceeds that of most reported metal–nitrogen coordination catalysts. Experimental and theoretical analyses reveal that high-purity pyrrole-type coordination significantly modifies the atomic and electronic structures of FeN₄ sites, bringing with it high intrinsic catalytic activity, preferable O₂ adsorption energy and full four-electron reaction selectivity for ORR catalysis. Therefore, PEMFCs built with this high-purity FeN₄ catalyst achieve a high open-circuit voltage (1.01 V) and a large peak power density (over 700 mW cm⁻²). High-purity iron–nitrogen coordination would give new insights into highly efficient electrocatalysts for PEMFCs.

中文翻译：

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高纯度吡咯型FeN4位点是优异的氧还原电催化剂

原子分散的铁-氮（FeN ₄）催化剂已成为质子交换膜燃料电池（PEMFC）中昂贵的基于Pt的对应物的最有希望的替代品，但由于铁-氮的多样性，它们经常遭受高电势和较差的稳定性的困扰协调结构。本文中，我们首次展示了高纯度的吡咯型FeN ₄位点，作为PEMFC的优良ORR电催化剂。高纯度吡咯型FeN ₄催化剂显示出非常出色的ORR活性，具有6.89 mA m ^-2的超高活性区电流密度在酸性介质中，超过了大多数报道的金属-氮配位催化剂。实验和理论分析表明，高纯度的吡咯型配位显着改变了FeN ₄位的原子和电子结构，使其具有高的固有催化活性，优选的O ₂吸附能和对ORR催化的全四电子反应选择性。因此，用该高纯度FeN ₄催化剂构建的PEMFC实现了高的开路电压（1.01V ）和大的峰值功率密度（超过700mW cm ^-2）。高纯度的铁-氮配位将为PEMFC的高效电催化剂提供新的见解。