中心电子富集的NO-FeN_(4)位点作为质子交换膜燃料电池的高级酸性氧还原反应电催化剂

Central electron-enriched NO-FeN_(4)sites as superior acidic oxy-gen reduction reaction electrocatalysts for proton exchange membrane fuel cells

开发非贵金属催化剂,特别是用于碳上铁氮(FeNC)材料的催化剂,对于质子交换膜燃料电池(PEMFC)的广泛应用是一个迫切需求。然而,传统铁氮位点在酸性条件下的氧还原反应(ORR)活性较差,严重阻碍了其电池性能的进一步提高。本文通过限域的小分子合成策略,大规模合成了具有一氧化氮(NO)基团轴向修饰的FeN_(4)(表示为NO-FeN_(4))。得益于NO基团的强吸电子效应,与传统的FeN_(4)样品相比,富含电子中心FeN_(4)位点表现出超高的ORR活性,具有三倍高的质量活性(0.85 V时为1.1 A·g^(−1)),以及全四电子反应选择性。此外,用所制备的电催化剂组装的质子交换膜燃料电池也表现出显著增强的峰值功率密度(>725 mW·cm^(−2))。这项工作为合理设计用于氧还原的先进M-Nx非贵金属电催化剂提供了一种新的方法。

Developing nobel-metal-free catalysts,especially for iron-nitrogen on carbon(FeNC)materials,has been an ur-gent demand for wide applications of proton exchange membrane fuel cells(PEMFCs).However,the inferior oxygen re-duction reaction(ORR)activity of traditional iron-nitrogen sites in acidic conditions seriously impedes the further im-provement of their performance.Herein,we synthesized FeN_(4)with NO(nitric oxide)group axial modification(denoted as NO-FeN_(4))on a large scale through a confined small molecule synthesis strategy.Benefitting from the strong electron-withdrawing effect of the NO group,the central electron-rich FeN_(4)site exhibits ultrahigh ORR activity with a three times higher mass activity(1.1 A·g^(−1)at 0.85 V)compared to the traditional FeN_(4)sample,as well as full four-electron reaction se-lectivity.Moreover,the PEMFC assembled with the as-prepared electrocatalyst also exhibits a greatly enhanced peak power density(>725 mW·cm^(−2)).This work provides a new approach to rationally design advanced M-Nx nonnoble elec-trocatalysts for the ORR.