<p>Metal single-atoms with optimized coordination structure on highly accessible substrate can maximize the metal utilization efficiency along with enhancing catalytic activities. Herein, axial nitrogen-coordinated Fe-N<sub>5</sub> sites on N-doped carbon (denoted as FeN<sub>5</sub>@N-C) hollow microplates are fabricated via a unique Fe<sup>3+</sup>-chelated polydopamine assisted hollowing strategy using ZIF-L microplates as multifunctional templates. Due to the powerful chelating and adhesive ability of polydopamine, this hollow-carbon strategy can be extended to fabricate single-atom Fe-N-C hollow structures with different shapes and encapsulate other transition-metal single atoms (Ni, Co, Mn, and Cu) into the N-doped carbon hollow microplates. The FeN<sub>5</sub>@N-C hollow microplates exhibit outstanding oxygen reduction reaction (ORR) capability with an impressive half-wave potential of 0.93 V vs. reversible hydrogen electrode and high stability, which can serve as air-cathode catalysts for high-performance Zn-air batteries with high peak power density of 225.3 mW cm<sup>−2</sup> and stable cyclability of up to 400 h. Comprehensive analysis and theoretical calculations elucidate that axial nitrogen coordination in Fe-N<sub>5</sub> catalytic sites, unlike the planar Fe-N<sub>4</sub> configuration, can compete well with the bonding of OH* through additional 3d-2p orbital hybridization, thereby giving moderate bonding strength to enhance the ORR activity.</p>

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Axial orbital hybridization enables single-atom Fe-N-C hollow microplates for efficient oxygen reduction

  • Fei-Xiang Ma,
  • Jianghua Wu,
  • Xiongyi Liang,
  • Guobin Zhang,
  • Zheng-Qi Liu,
  • Hong-Shuang Fan,
  • Jian Lu,
  • Cheng-Yan Xu,
  • Xiao Cheng Zeng,
  • Yang Yang Li

摘要

Metal single-atoms with optimized coordination structure on highly accessible substrate can maximize the metal utilization efficiency along with enhancing catalytic activities. Herein, axial nitrogen-coordinated Fe-N5 sites on N-doped carbon (denoted as FeN5@N-C) hollow microplates are fabricated via a unique Fe3+-chelated polydopamine assisted hollowing strategy using ZIF-L microplates as multifunctional templates. Due to the powerful chelating and adhesive ability of polydopamine, this hollow-carbon strategy can be extended to fabricate single-atom Fe-N-C hollow structures with different shapes and encapsulate other transition-metal single atoms (Ni, Co, Mn, and Cu) into the N-doped carbon hollow microplates. The FeN5@N-C hollow microplates exhibit outstanding oxygen reduction reaction (ORR) capability with an impressive half-wave potential of 0.93 V vs. reversible hydrogen electrode and high stability, which can serve as air-cathode catalysts for high-performance Zn-air batteries with high peak power density of 225.3 mW cm−2 and stable cyclability of up to 400 h. Comprehensive analysis and theoretical calculations elucidate that axial nitrogen coordination in Fe-N5 catalytic sites, unlike the planar Fe-N4 configuration, can compete well with the bonding of OH* through additional 3d-2p orbital hybridization, thereby giving moderate bonding strength to enhance the ORR activity.