Recent advances in carbon-supported iron group electrocatalysts for the oxygen reduction reaction
摘要: 金属-空气电池作为新兴的能源装置受到了人们的关注。氧还原反应(ORR)是金属-空气电池的关键电化学过程。由于氧还原反应缓慢的动力学速率和铂基ORR催化剂高昂的价格严重阻碍了金属-空气电池的规模化应用。铁系元素不但地球储量丰富而且具有多样的杂化轨道，将铁系元素引入到炭骨架中可以实现与铂相近的催化性能，非常有希望取代铂基催化剂成为商用ORR催化剂。本文根据活性位点的分类，对铁系元素基炭催化剂在ORR中的应用进行了综述，并系统总结了各中活性位点在ORR过程中的作用机理。本文在系统论述炭负载铁系元素催化剂结构和性能间构效关系的基础上，充分认识铁系元素在ORR中的作用，为今后设计具有高效ORR催化性能的廉价催化剂提供技术支撑和理论指导。Abstract: Metal-air batteries are emerging energy devices that have received worldwide attention. The oxygen reduction reaction (ORR) is the key electrochemical process of metal-air batteries. The sluggish nature of ORR kinetics and the high cost of Pt-based ORR catalysts have severely hindered their large-scale application. As earth-abundant elements, the iron group elements have a variety of hybrid orbitals, and their incorporation into the carbon skeleton achieves good ORR catalytic activity, giving them great potential for substituting for Pt-based catalysts. Here, their uses for ORR and the function of each active site in the ORR process are summarized. The relationship between the microstructure and performance of these catalysts may help us fully understand the role of iron group elements in ORR and provide basic insight into the design of cheap catalysts with outstanding ORR catalytic performance in the future.
Figure 1. Summary of carbon-supported iron series element catalysts in ORR, such as Fe-Nx (Reprinted with permission by copyright 2021, Willey), Fe-Ox (Reprinted with permission by copyright 2020, Willey), Fe-Px (Reprinted with permission by copyright 2020, ACS), Ni-Nx (Reprinted with permission by copyright 2020, RSC), Ni-Sx (Reprinted with permission by copyright 2018, ACS), Ni NPs (Reprinted with permission by copyright 2017, Willey), Ni-Ox (Reprinted with permission by copyright 2020, Springer Nature), Co NPs (Reprinted with permission by copyright 2020, Willey), Co-Sx (Reprinted with permission by copyright 2019, Willey), Co-Px (Reprinted with permission by copyright 2019, RSC), Co-Nx (Reprinted with permission by copyright 2020, Willey) and Fe-Cx (Reprinted with permission by copyright 2020, Elsevier).
Figure 2. (a) The synthesis procedure of FeNC-D0.5 (Reprinted with permission by copyright 2021, Willey), (b) the energetic pathway of the ORR on Co4N@NC (Reprinted with permission by copyright 2020, Elsevier), (c) the correlation between the onset potential (
Uonset) and adsorption energy ( Eads) of the adsorptive oxygen atoms on CoN4−xCx, (d) the Bader charge transfer of the adsorptive oxygen on CoN4−xCx sites (Reprinted with permission by copyright 2020, Willey), (e) free energy diagram for O2 reduction on Ni–N2 edge defect (Reprinted with permission by copyright 2012, ACS) and (f) free energy diagram for ORR on three-coordinated NiN3, NiN2C, NiNC2, NiC3 at the equilibrium potential (U=0.402 V) in alkaline conditions (Reprinted with permission by copyright 2020, RSC).
Figure 3. (a) Schematic illustration of the synthesis for Fe2P/NPC, (b) rotating ring disk electrode (RRDE) voltammograms of Fe2P/NPC, NPC, and Pt/C in O2-saturated 0.10 mol L−1 KOH solution (Reprinted with permission by copyright 2020, Elsevier), (c) high resolution-transmission electron microscope (HR-TEM) images of Co2P/CoNPC, (d) the linear sweep voltammetry (LSV) curves of Co2P/CoNPC (Reprinted with permission by copyright 2020, Willey) and (e) free energy diagrams for ORR at different electrode potentials on CoP (211) surface through the oxygen associative mechanism (Reprinted with permission by copyright 2018, Willey).
Figure 4. (a) Schematic illustration for the synthesis of NP-Co3O4/CC, (b) polarization curves of various catalysts, (c) the ORR stability evaluation of NP-Co3O4/CC and Pt/C (Reprinted with permission by copyright 2020, Elsevier) and (d) schematic illustration of possible ORR mechanisms using Co3O4@NGC@MP-TiO2 catalyst (Reprinted with permission by copyright 2021, Elsevier).
Figure 6. (a) Schematic illustration of the preparation of Co@SNHC (Reprinted with permission by copyright 2019, RSC) , (b) rotating disk electrode (RDE) polarization curves of Ni@N-CNCs, N-CNCs, and Ni/N-CNCs and (c) chronoamperometric response of Pt/C, Ni@N-CNCs, and N-CNCs at −0.4 V and 1600 r/min (Reprinted with permission by copyright 2017, Willey).
Figure 7. (a) Schematic illustration of the preparation of Fe3C/C-700 (Reprinted with permission by copyright 2014, Willy), (b) the linear correlation of adsorption energies for intermediates during ORR, (c) the energetic pathway of the ORR on Fe3C@MHNFs and (d) polarization curves of MHNFs, Fe3C@SNFs, Fe3C@MHNFs and commercial Pt/C (Reprinted with permission by copyright 2020, RSC).
Figure 8. (a) XRD patterns of the Fe2O3@NC-450 (Reprinted with permission by copyright 2020, RSC), (b) high-angle annular dark field-scanning transmission election microscope (HAADF-STEM) images of FeSA/FeONC/NSC, (c) Fe K-edge k3-weighted Fourier transform (FT) spectra of FeSA/FeONC/NSC, Fe2O3 and Fe foil (Reprinted with permission by copyright 2020, RSC) and (d) schematic illustration of the preparation of Ni/NiO/NiCo2O4/N-CNT-As (Reprinted with permission by copyright 2016, RSC).
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