Sui Rui, Liu Bo, Chen Chang, Tan Xin, He Chang, Xin Dongyue, Chen Bowen, Xu Zhiyuan, Li Jiazhan, Chen Wenxing, Zhuang Zhongbin, Wang Zhenbo, Chen Chen
Engineering Research Center of Advanced Rare Earth Materials, Department of Chemistry, Tsinghua University, Beijing 100084, China.
MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion and Storage, State Key Laboratory of Space Power-Sources, School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001, China.
J Am Chem Soc. 2024 Sep 25;146(38):26442-26453. doi: 10.1021/jacs.4c09642. Epub 2024 Sep 12.
Iron-nitrogen-carbon (Fe-N-C) materials have been identified as a promising class of platinum (Pt)-free catalysts for the oxygen reduction reaction (ORR). However, the dissolution and oxidation of Fe atoms severely restrict their long-term stability and performance. Modulating the active microstructure of Fe-N-C is a feasible strategy to enhance the ORR activity and stability. Compared with common 3d transition metals (Co, Ni, etc.), the 4d transition metal atom Nb has fewer d electrons and more unoccupied orbitals, which could potentially forge a more robust interaction with the Fe site to optimize the binding energy of the oxygen-containing intermediates while maintaining stability. Herein, an asymmetric Fe-Nb diatomic site catalyst (FeNb/c-SNC) was synthesized, which exhibited superior ORR performance and stability compared with those of Fe single-atom catalysts (SACs). The strong interaction within the Fe-Nb diatomic sites optimized the desorption energy of key intermediates (*OH), so that the adsorption energy of Fe-*OH approaches the apex of the volcano plot, thus exhibiting optimal ORR activity. More importantly, introducing Nb atoms could effectively strengthen the Fe-N bonding and suppress Fe demetalation, causing an outstanding stability. The zinc-air battery (ZAB) and hydroxide exchange membrane fuel cell (HEMFC) equipped with our FeNb/c-SNC could deliver high peak power densities of 314 mW cm and 1.18 W cm, respectively. Notably, the stable operation time for ZAB and HEMFC increased by 9.1 and 5.8 times compared to Fe SACs, respectively. This research offers further insights into developing stable Fe-based atomic-level catalytic materials for the energy conversion process.
铁氮碳（Fe-N-C）材料已被确认为一类有前景的无铂氧还原反应（ORR）催化剂。然而，铁原子的溶解和氧化严重限制了它们的长期稳定性和性能。调控Fe-N-C的活性微观结构是提高ORR活性和稳定性的可行策略。与常见的3d过渡金属（Co、Ni等）相比，4d过渡金属原子Nb的d电子较少且未占据轨道较多，这可能与Fe位点形成更强健的相互作用，从而在保持稳定性的同时优化含氧中间体的结合能。在此，合成了一种不对称的Fe-Nb双原子位点催化剂（FeNb/c-SNC），与Fe单原子催化剂（SACs）相比，其表现出优异的ORR性能和稳定性。Fe-Nb双原子位点内的强相互作用优化了关键中间体（*OH）的脱附能，使得Fe-*OH的吸附能接近火山图的顶点，从而展现出最佳的ORR活性。更重要的是，引入Nb原子可有效强化Fe-N键并抑制Fe的脱金属化，从而具有出色的稳定性。配备我们的FeNb/c-SNC的锌空气电池（ZAB）和氢氧化物交换膜燃料电池（HEMFC）分别可提供314 mW cm²和1.18 W cm²的高峰功率密度。值得注意的是，ZAB和HEMFC的稳定运行时间分别比Fe SACs增加了9.1倍和5.8倍。这项研究为开发用于能量转换过程的稳定铁基原子级催化材料提供了进一步的见解。
