Template-Free Fabrication of Single Atom Fe-Based Cathodes Unlock High-Performing Anion-Exchange Membrane Fuel Cells

Single‐atom catalysts (SACs) possessing well‐defined active sites of singular metal atoms have gained prominence in the field of electrocatalysis as they can be tuned to enhance activity and stability. In this study, a critical‐raw‐material (CRM)‐free SAC is synthesized for the oxygen reduction reaction (ORR) in alkaline media by pyrolyzing polyimide nanoparticles and Fe without using a sacrificial template. Upon purification, the resulting catalyst demonstrates outstanding performance as cathodes in anion‐exchange membrane fuel cells (AEMFCs) owing to sufficiently stabilized Fe single‐atoms at the FeN₄ sites yielding a peak power density (<i>P</i>_max) as high as ∼1.8 W cm⁻² and specific power values up to 11.3 W mg_PGM^-1; the latter being the greatest reported among CRM‐free cathode AEMFCs. The SAC also shows remarkable in situ durability under a very high current density of 1000 mA cm⁻², a first introduced here, with only a 2 mV h⁻¹ decay. Most impressively, when the SAC is combined with a NiMo anode to test a completely CRM‐free high‐temperature (HT)‐AEMFC at 118 °C, a <i>P</i>_max of 372 mW cm⁻²and limiting current density of ∼1.14 A cm⁻² are achieved. This work represents a significant milestone in the development of durable SAC cathode catalysts for the next generation of CRM‐free AEMFCs.

拥有明确单金属原子活性位点的单原子催化剂（Single‐atom catalysts, SACs）可通过调控提升催化活性与稳定性，因此在电催化领域受到广泛关注。本研究无需使用牺牲模板，通过热解聚酰亚胺纳米颗粒与铁（Fe），合成了一款无关键原材料（critical‐raw‐material, CRM）的单原子催化剂，用于碱性介质中的氧还原反应（oxygen reduction reaction, ORR）。经纯化处理后，所得催化剂作为阴离子交换膜燃料电池（anion‐exchange membrane fuel cells, AEMFCs）阴极展现出优异性能：稳定锚定在FeN₄位点的铁单原子使其峰值功率密度（<i>P</i>_max）高达约1.8 W·cm⁻²，比功率最高可达11.3 W·mg_PGM⁻¹（其中PGM指铂族金属，platinum group metal），该比功率数值为无关键原材料阴极阴离子交换膜燃料电池领域已报道的最高值。该单原子催化剂在1000 mA·cm⁻²的超高电流密度下仍表现出出色的原位耐久性，仅以2 mV·h⁻¹的速率衰减，该测试条件为本次研究首次引入。最引人注目的是，将该单原子催化剂与镍钼（NiMo）阳极结合，在118 ℃下测试完全无关键原材料的高温阴离子交换膜燃料电池（high‐temperature, HT-AEMFC）时，实现了372 mW·cm⁻²的峰值功率密度和约1.14 A·cm⁻²的极限电流密度。本研究为下一代无关键原材料阴离子交换膜燃料电池用高耐久性单原子催化剂阴极的开发树立了重要里程碑。