A Versatile Approach to Boost Oxygen Reduction of Fe-N4 Sites by Controllably Incorporating Sulfur Functionality

作者：Shao, Chunfeng; Wu, Liming; Zhang, Haocheng; Jiang, Qike; Xu, Xiaoyan; Wang, Yinghua; Zhuang, Shiguang; Chu, Hailiang; Sun, Lixian; Ye, Jianshan; Li, Baitao^*; Wang, Xiujun^*

来源：Advanced Functional Materials, 2021, 31(25): 2100833.

DOI：10.1002/adfm.202100833

• air cathodes
• functional groups
• iron&#8208
• nitrogen carbon
• oxygen reduction reaction
• single&#8208
• atom catalysts

Although atomically dispersed Fe-N-4 on carbon materials (Fe-NC) have enormous potential for the oxygen reduction reaction (ORR), precise control over the electronic structure of Fe to enhance the catalytic performance and a full understanding of the catalytic mechanism remain elusive. Herein, a novel approach is designed to boost the kinetic activity of single Fe-N-4 centers by controlling S-doped content and species (namely, thiophene-like S and oxidized S). Due to confinement and catalysis effects, the innovative strategy of combining a Mg(OH)(2) template with KOH activation preferentially generates oxidized S and simultaneously constructs porous carbon with a high Fe loading (2.93 wt%) and hierarchical pores. Theoretical calculations suggest that neighboring S functionalities can affect the electronic configurations of Fe-N-4 sites and increase the electron density around Fe atoms, thereby optimizing the adsorption energy of intermediates and substantially accelerating reaction kinetics, following the trend: oxidized S doped > thiophene-like S doped > pristine Fe-N-4. Benefiting from high activity and accessibility of Fe-N-4 sites, the optimal FeNC-SN-2 electrode displays impressive ORR activity with large power density while maintaining outstanding durability in Zn-air batteries and microbial fuel cells. The work paves the way to prepare stable single-atom metal-N-x sites with heteroatom-doping for diverse high-performance applications.

• 单位
  桂林电子科技大学; 中国科学院