摘要 随着阴离子交换膜的出现、发展和应用，碱性燃料电池的优势日趋明显，针对碱性燃料电池的研究也更广泛而深刻. 在碱性燃料电池中，除了其固有的对催化剂的高包容性和动力学优越性，阴离子交换膜让阴离子定向迁移，从而实现了很好的水相管理，降低了电池中“水涝”的几率，也提供了更广阔的燃料选择空间. 氧还原反应是碱性燃料电池中的重要部分，且其反应动力学相较于氢氧化反应缓慢. 因此，选择并研制合适的阴极氧还原反应催化剂，是提高碱性燃料电池性能和促进燃料电池规模化使用的关键. Fe-N-C类催化剂因其在碱性条件下接近甚至优于 Pt 基催化剂的性能，被视为最有潜力替代 Pt 的非贵金属催化剂. 本文从近 5 年来 Fe-N-C 类催化剂的合成方法、催化活性位点和氧还原反应机理以及在燃料电池中的应用三方面进行了综述. Fuel cells are highly recommended nowadays due to their intrinsic advantages such as high energy conversion efficiency, nearly no pollution, and convenient operation. With the development of anion exchange membrane, alkaline fuel cells have gone through a renaissance thanks to their superiorities such as faster reaction kinetics, wider choices for both fuels and electrocatalysts. It is essential to find an appropriate electrocatalyst for oxygen reduction reaction (ORR) to improve the performance of alkaline fuel cells. Further commercialization of the widely used Pt-based materials has suffered from disadvantages such as scarcity and high cost. As alternatives to largely investigated Pt-based materials, Fe-N-C electrocatalysts have gained increasing attention. However, Fe-N-C electrocatalysts still face problems including imperfect stability and durability, low metal loading, unclear catalytic mechanism and active sites, which has further hindered their design and synthesis. In this review, Fe-N-C electrocatalysts for alkaline fuel cells are discussed from the following three aspects, namely, the synthesis methods, the active sites and mechanisms, and their applications in recent five years. To optimize synthetic conditions, two kinds of typical synthetic methods are overviewed and some synthetic examples in the recent five years are summarized. Three active sites such as FeN4/C, Fe-N2+2/C, and Fe-N2/C, as well as those active sites concerned more widely in recent research for Fe-N-C electrocatalysts are also reviewed, which lays a good foundation for future design of Fe-N-C electrocatalysts. Furthermore, the single cell performance data are provided for the first time in order to enhance the application of the Fe-N-C electrocatalysts in alkaline fuel cells. As a whole, this review aims at providing theoretical support and guidance for future design and synthesis of commercial Fe-N-C electrocatalysts
Wang Z L, Xu D, Zhong H X, et al. Gelatin-derived sustainable carbon-based functional materials for energy conversion and storage with controllability of structure and component[J]. Science Advances, 2015, 1(1): 1400035-1400035.
Wang X X, Wang B, Zhong J, et al. Iron polyphthalocyanine sheathed multiwalled carbon nanotubes: A high-performance electrocatalyst for oxygen reduction reaction[J]. Nano Research, 2016, 9(5): 1497-1506.
Zhong W H, Chen J X, Zhang P X, et al. Air plasma etching towards rich active sites in Fe/N-porous carbon for oxygen reduction reaction with superior catalytic performance[J]. Journal of Materials Chemistry A, 2017, 5(32): 16605-16610.
Xiang Z H, Xue Y H, Cao D P, et al. Highly efficient electrocatalysts for oxygen reduction based on 2D covalent organic polymers complexed with non-precious metals[J]. Angewandte Chemie-International Edition, 2014, 53(9): 2433-2437.
Miller H A, Bellini M, Oberhauser W, et al. Heat treated carbon supported iron(ii) phthalocyanine oxygen reduction catalysts: Elucidation of the structure-activity relationship using X-ray absorption spectroscopy[J]. Physical Chemistry Chemical Physics, 2016, 18(48): 33142-33151.
Vante N A, Jaegermann W, Tributsch H, et al. Electrocatalysis of oxygen reduction by chalcogenides containing mixed transition metal clusters[J]. Journal of the American Chemical Society 1987, 109(11): 3251-3257.
Sa Y J, Seo D J, Woo J, et al. A general approach to preferential formation of active Fe-N-x sites in Fe-N/C electrocatalysts for efficient oxygen reduction reaction[J]. Journal of the American Chemical Society, 2016, 138(45): 15046-15056.
Cui X, Yang S, Yan X, et al. Pyridinic-nitrogen-dominated graphene aerogels with Fe-N-C coordination for highly efficient oxygen reduction reaction[J]. Advanced Functional Materials, 2016, 26(31): 5708-5717.
Lai L, Potts J R, Zhan D, et al. Exploration of the active center structure of nitrogen-doped graphene-based catalysts for oxygen reduction reaction[J]. Energy & Environmental Science, 2012, 5(7): 7936-7942.
Herranz J, Jaouen F, Lefèvre M, et al. Unveiling N-protonation and anion-binding effects on Fe/N/C catalysts for O2 reduction in proton-exchange-membrane fuel cells[J]. Journal of Physical Chemistry C, 2011, 115(32): 16087-16097.
Schulenburg H, Stankov S, Schünemann V, et al. Catalysts for the oxygen reduction from heat-treated iron(III) tetramethoxyphenylporphyrin chloride: Structure and stability of active sites[J]. The Journal of Physical Chemistry B, 2003, 107(34): 9034-9041.
Van Veen J R, Van Baar J F, Kroese K J. Effect of heat treatment on the performance of carbon-supported transition-metal chelates in the electrochemical reduction of oxygen[J]. Journal of The Chemical Society-Faraday Transactions I, 1981, 77(11): 2827-2843.
Jiang W J, Gu L, Li L, et al. Understanding the high activity of Fe-N-C electrocatalysts in oxygen reduction: Fe/Fe3C nanoparticles boost the activity of Fe-Nx[J]. Journal of the American Chemical Society, 2016, 138(10): 3570-3578.
Kang H L, Cho D H, Kim Y M, et al. Highly conductive and durable poly(arylene ether sulfone) anion exchange membrane with end-group cross-linking[J]. Energy & Environmental Science, 2017, 10(1): 275-285.
Ng J W D, Gorlin Y, Nordlund D, et al. Nanostructured manganese oxide supported onto particulate glassy carbon as an active and stable oxygen reduction catalyst in alkaline-based fuel cells[J]. Journal of The Electrochemical Society, 2014, 161(7): 3105-3112.
He Q G, Li Q, Khene S, et al. High-loading cobalt oxide coupled with nitrogen-doped graphene for oxygen reduction in anion-exchange-membrane alkaline fuel cells[J]. Journal of Physical Chemistry C, 2013, 117(17): 8697-8707.
Mamlouk M, Kumar S M S, Gouerec P, et al. Electrochemical and fuel cell evaluation of Co based catalyst for oxygen reduction in anion exchange polymer membrane fuel cells[J]. Journal of Power Sources, 2011, 196(18): 7594-7600
Ramaswamy N, Mukerjee S. Influence of inner-and outer-sphere electron transfer mechanisms during electrocatalysis of oxygen reduction in alkaline media[J]. The Journal of Physical Chemistry C, 2011, 115(36): 18015-18026.
Domínguez C, Pérez-Alonso F J, Salam M A, et al. Repercussion of the carbon matrix for the activity and stability of Fe/N/C electrocatalysts for the oxygen reduction reaction[J]. Applied Catalysis B-Environmental, 2016, 183: 185-196.
Chen C, Yang X D, Zhou Z Y, et al. Aminothiazole-derived N,S,Fe-doped graphene nanosheets as high performance electrocatalysts for oxygen reduction[J]. Chemical Communications 2015, 51(96): 17092-17095.
Wu G, Johnston C M, Mack N H, et al. Synthesis-structure-performance correlation for polyaniline-Me-C nonprecious metal cathode catalysts for oxygen reduction in fuel cells[J]. Journal of Materials Chemistry, 2011, 21(30): 11392-11405.
Chen C（陈驰）, Lai Y J（赖愉姣）, Zhou Z Y（周志有）, et al. Thermo-stability and active site structure of Fe/N/C electrocatalyst for oxygen reduction reaction[J]. Journal of Electrochemistry（电化学）, 2017, 23(4): 400-408.
Artyushkova K, Kiefer B, Halevi B, et al. Density functional theory calculations of XPS binding energy shift for nitrogen-containing graphene-like structures[J]. Chemical Communications, 2013, 49(25): 2539-2541.
Unni S M, Devulapally S, Karjule N, et al. Graphene enriched with pyrrolic coordination of the doped nitrogen as an efficient metal-free electrocatalyst for oxygen reduction[J]. Journal of Materials Chemistry, 2012, 22(44): 23506-23513.
Bouwkamp-Wijnoltz A L, Visscher W, Veen J A R V, et al. On active-site heterogeneity in pyrolyzed carbon-supported iron porphyrin catalysts for the electrochemical reduction of oxygen: An in situ m？issbauer study[J]. Journal of Physical Chemisty B, 2002, 106(50): 12993-13001.
M L, Dodelet J P, Bertrand P. Molecular oxygen reduction in PEM fuel cells: Evidence for the simultaneous presence of two active sites in Fe-based catalysts[J]. Journal of Physical Chemisty B, 2002, 106(34): 8705-8713.
Franke R, Ohms D, Wiesener K. Investigation of the influence of thermal treatment on the properties of carbon materials modified by N4-chelates for the reduction of oxygen in acidic media[J]. Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 1989, 260(1): 63-73.
Wen Z H, Ci S Q, Zhang F, et al. Nitrogen-enriched core-shell structured Fe/Fe(3)C-C nanorods as advanced electrocatalysts for oxygen reduction reaction[J]. Advanced Materials, 2012, 24(11): 1399-1404.
Charreteur F, Jaouen F, Ruggeri S, et al. Fe/N/C non-precious catalysts for PEM fuel cells: Influence of the structural parameters of pristine commercial carbon blacks on their activity for oxygen reduction[J]. Electrochimica Acta, 2008, 53(6): 2925-2938.
Sa Y J, Park C, Jeong H Y, et al. Carbon nanotubes/heteroatom-doped carbon core-sheath nanostructures as highly active, metal-free oxygen reduction electrocatalysts for alkaline fuel cells[J]. Angewandte Chemie International Edition, 2014, 53(16): 4102-4106.
Lee S, Choun M, Ye Y, et al. Designing a highly active metal-free oxygen reduction catalyst in membrane electrode assemblies for alkaline fuel cells: Effects of pore size and doping-site position[J]. Angewandte Chemie-International Edition, 2015, 54(32): 9230-9234.
Dong G, Huang M, Guan L. Iron phthalocyanine coated on single-walled carbon nanotubes composite for the oxygenreduction reaction in alkaline media[J]. Physical Chemistry Chemical Physics, 2012, 14(8): 2557-2559.
Jaouen F, Proietti E, Lefèvre M, et al. Recent advances in non-precious metal catalysis for oxygen-reduction reaction in polymer electrolyte fuel cells[J]. Energy & Environmental Science, 2010, 4(1): 114-130.
Rauf M, Chen R, Wang Q, et al. Nitrogen-doped carbon nanotubes with encapsulated Fe nanoparticles as efficient oxygen reduction catalyst for alkaline membrane direct ethanol fuel cells[J]. Carbon, 2017, 125, 605-613.
Niu W H, Li L G, Liu X J, et al. Mesoporous N-doped carbons prepared with thermally removable nanoparticle templates: An efficient electrocatalyst for oxygen reduction reaction[J]. Journal of the American Chemical Society, 2015, 137(16): 5555-5562.
Negro E, Videla A H A M, Baglio V, et al. Fe-N supported on graphitic carbon nano-networks grown from cobalt as oxygen reduction catalysts for low-temperature fuel cells[J]. Applied Catalysis B Environmental, 2015, 166: 75-83.
He Q G, Cairns E J. Review—Recent progress in electrocatalysts for oxygen reduction suitable for alkaline anion exchange membrane fuel cells[J]. Journal of The Electrochemical Society, 2015, 162(14): 1504-1539.
Deavin O I, Murphy S, Ong A L, et al. Anion-exchange membranes for alkaline polymer electrolyte fuel cells: Comparison of pendent benzyltrimethylammonium-and benzylmethylimidazolium-head-groups[J]. Energy & Environmental Science 2012, 5(9): 8584-8597.
Mo G, Liao S, Zhang Y, et al. Synthesis of active iron-based electrocatalyst for the oxygen reduction reaction and its unique electrochemical response in alkaline medium[J]. Electrochimica Acta 2012, (76): 430-439.
Zeng L, Cui X, Chen L, et al. Non-noble bimetallic alloy encased in nitrogen-doped nanotubes as a highly active and durable electrocatalyst for oxygen reduction reaction[J]. Carbon, 2016, 114: 347-355.
Meng F L, Wang Z L, Zhong H X, et al. Reactive multifunctional template-induced preparation of Fe-N-doped mesoporous carbon microspheres towards highly efficient electrocatalysts for oxygen reduction[J]. Advanced Materials, 2016, 28(36): 7948-7955.
Li Z L, Li G L, Jiang L H, et al. Ionic liquids as precursors for efficient mesoporous iron-nitrogen-doped oxygen reduction electrocatalyst[J]. Angewandte Chemie-International Edition, 2015, 54(5): 1494-1498.
Lin L, Zhu Q, Xu A W. Noble-metal-free Fe-N/C catalyst for highly efficient oxygen reduction reaction under both alkaline and acidic conditions[J]. Journal of the American Chemical Society, 2014, 136(31): 11027-11033.
Chen C（陈驰）, Zhou Z Y（周志有）, Zhang X S（张新胜）, et al. Synthesis of Fe,N-doped graphene/carbon black composite with high catalytic activity for oxygen reduction reaction[J]. Journal of Electrochemistry（电化学）, 2016, 22(1): 25-31.
Mun Y, Min J K, Park S A, et al. Soft-template synthesis of mesoporous non-precious metal catalyst with Fe-Nx/C active sites for oxygen reduction reaction in fuel cells[J]. Applied Catalysis B-Environmental, 2017, 222: 191-199.