Zn3[Fe(CN)6]2 derived Fe/Fe5C2@N-doped carbon as a highly effective oxygen reduction reaction catalyst for zinc-air battery
Graphical abstract
Introduction
Large numbers of researches have been carried out to develop alternative energy storage and conversion devices such as fuel cells and metal-air batteries. For the mass production of these promising devices, highly active cathode catalyst to enhance the efficiency of oxygen reduction reaction (ORR) is distinctly important because the sluggish kinetics at the cathode is the major technical challenge. Pt-based materials have been still by far the most efficient electrocatalyst while the scarcity, high cost and poor stability greatly limit their widespread applications. Recently intensive research efforts in reducing or replacing Pt-based catalysts have led to the development of new ORR electrocatalysts, including Pt-based alloys [[1], [2], [3]], metal-free carbon materials [4,5], conducting polymers [6], and transition metal/heteroatom doped carbon composites [7]. Among them, transition metal (e.g., nickel, cobalt, iron) and nitrogen doped carbon (Me-N-C) has attracted tremendous research interest as a promising electrocatalyst toward ORR [[8], [9], [10], [11]]. However, in terms of the activity and durability, significant gaps between the Me-N-C and precious metal catalysts remain to be eliminated for viable application. The active sites of Me-N-C catalysts are generally speculated to be associated with N coordinated metal structures (M-Nx) with average coordination number x from 2 to 4 through X-ray absorption or Mössbauer spectroscopy techniques [12,13]. A key method for the Me-N-C catalysts to enhance the electrocatalytic activity is to offer the sufficient exposure of the active Me-Nx sites in carbon composite materials by accurate control of the catalyst composition and structure. Despite tremendous efforts, the relatively slow kinetics of the ORR continues to be a bottleneck because of the complicated multielectron transfer process. Furthermore, some catalysts always suffer from structural degradation or catalytic centers poisoning during electrochemical processes, thus resulting in poor durability. For the Me-N-C catalysts, the metal sites are easy to fall off from the carbon matrix [14]. It is beneficial to design a highly active and durable catalyst with rich metal sites and rational core-shell structure, in which the metal sites are encased by the thin graphitic layer, not only protecting the metal sites from aggregation and dissolution, but also coupling metal sites and N-doped carbon acting as the active sites. Many researches have reported that carbon encapsuled metal or metal carbide is in favor of electrocatalysis [[15], [16], [17], [18]], due to the synergistic effect between metal/metal carbide and protective nitrogen-doped graphitic layers, thus facilitating interfacial charge transfer and improving proton reduction ability [19,20].
Recently, metal-organic frameworks (MOFs) are attracting lots of interests in catalytic fields due to the unique features such as large specific surface area, controllable pore texture and tuneable composition. For example, Zhang et.al synthesized novel Co@N-C bifunctional catalysts derived from a pair of enantiotopic chiral 3D MOFs for highly efficient zinc-air battery and water splitting [17]. Prussian blue analogue, as a cyano ligand-bridged MOF, has been widely used as the precursor material in the fields of water splitting and energy storage [[21], [22], [23]]. Here we developed a facile strategy to synthesize highly active Fe/Fe5C2@N-C ORR electrocatalyst from a Prussian blue analogue Zn3[Fe(CN)6]2 and applied it to the zinc-air battery. The iron species facilitate the graphitization process and improve the ORR activity together with outside N-doped graphic carbon. In addition, the volatile zinc help to produce a porous structure and improve the dispersity of iron species during the pyrolysis process. As a result, Fe/Fe5C2@N-C-1000 (annealed in 1000 °C) was tested to have the highest ORR activity, comparable to that of Pt/C.
Section snippets
Catalysts synthesis
The Prussian blue analogue Zn3[Fe(CN)6]2 was synthesized with a precipitation method. First, 6 mmol ZnCl2 (0.818 g) was dissolved in 50 mL deioinized water. Then 4 mmol K3[Fe(CN)6] (1.317 g) together with 0.6 g PVP (Polyvinyl Pyrrolidone, K30) was dissolved in 50 mL deioinized water. The above two solutions were mixed together with 30 min magnetic stirring and kept in the dark for 6 h. The resultant brown precipitates were collected by centrifugation, consecutively washed with distilled water
Results and discussion
The fabrication of Fe/Fe5C2@N-C is on the base of wet precipitation method and subsequent heat-treatment as illustrated in Fig. 1. The Zn3[Fe(CN)6]2 precipitate comes into being after the mixture of aqueous ZnCl2 and K3[Fe(CN)6], forming spherical particles at the assistance of PVP. Zn3[Fe(CN)6]2 is constructed by the cross-linking of zinc and the nitrogen atom within the hexacyanoferrate [Fe(CN)6]3+ group, thus forming a 3D continuous framework with abundant Fe, N, C and Zn. Fig. S1 shows the
Conclusions
In summary, Fe/Fe2C5 wrapped in N-doped carbon (Fe/Fe5C2@N-C) was fabricated by annealing decomposition of a zinciferous Prussian blue analogue Zn3[Fe(CN)6]2. The obtained Fe/Fe5C2@N-C-1000 catalyst exhibits an excellent ORR activity and a superior stability, especially in alkaline electrolyte, which are due to the rich iron/iron carbide particles and protective N-doped graphitic carbon shells. In addition, served as an air cathode material for zinc-air battery, Fe/Fe5C2@N-C-1000 demonstrates a
Acknowledgements
This work was financially supported by the National Natural Science Foundation of China (11575084 and 51602153), the Natural Science Foundation of Jiangsu Province (BK20160795), Nanjing University of Aeronautics and Astronautics PhD Short-term Visiting Scholar Project, Funding of Jiangsu Innovation Program for Graduate Education (KYCX17_0250), Funding for Outstanding Doctoral Dissertation in NUAA (BCXJ17-09) and A Project Funded by the Priority Academic Program Development of Jiangsu Higher
References (48)
- et al.
Single-atom catalysts: synthetic strategies and electrochemical applications
Joule
(2018) - et al.
Fe3C nanoparticle decorated Fe/N doped graphene for efficient oxygen reduction reaction electrocatalysis
J. Power Sources
(2016) - et al.
Structure and magnetic properties of copper (II) hexacyanoferrate (III) compound
J. Phys. Chem. Solids
(2001) - et al.
Nitrogen-doped hierarchically porous carbon foam: a free-standing electrode and mechanical support for high-performance supercapacitors
Nano Energy
(2016) - et al.
Tuning the activity of Pt alloy electrocatalysts by means of the lanthanide contraction
Science
(2016) - et al.
High-performance transition metal–doped Pt3Ni octahedra for oxygen reduction reaction
Science
(2015) - et al.
Ordered Pt3Co intermetallic nanoparticles derived from metal-organic frameworks for oxygen reduction
Nano Lett.
(2018) - et al.
A metal-free bifunctional electrocatalyst for oxygen reduction and oxygen evolution reactions
Nat. Nanotechnol.
(2015) - et al.
Nitrogen-doped carbon nanotube arrays with high electrocatalytic activity for oxygen reduction
Science
(2009) - et al.
Redox-active and semi-conducting donor–acceptor conjugated microporous polymers as metal-free ORR catalysts
J. Mater. Chem. A
(2018)
High-performance electrocatalysts for oxygen reduction derived from polyaniline, iron, and cobalt
Science
Hollow N-doped carbon spheres with isolated cobalt single atomic sites: superior electrocatalysts for oxygen reduction
J. Am. Chem. Soc.
Electronic structure engineering to boost oxygen reduction activity by controlling the coordination of the central metal
Energy Environ. Sci.
A polymer encapsulation strategy to synthesize porous nitrogen–doped carbon–nanosphere–supported metal isolated–single–atomic–site catalysts
Adv. Mater.
Single atomic iron catalysts for oxygen reduction in acidic media: particle size control and thermal activation
J. Am. Chem. Soc.
Isolated single iron atoms anchored on N-doped porous carbon as an efficient electrocatalyst for the oxygen reduction reaction
Angew. Chem. Int. Ed.
Active salt/silica-templated 2D mesoporous FeCo-Nx-carbon as bifunctional oxygen electrodes for zinc–air batteries
Angew. Chem. Int. Ed.
M3C (M: Fe, Co, Ni) nanocrystals encased in graphene nanoribbons: an active and stable bifunctional electrocatalyst for oxygen reduction and hydrogen evolution reactions
ACS Nano
Understanding the high activity of Fe–N–C electrocatalysts in oxygen reduction: Fe/Fe3C nanoparticles boost the activity of Fe–Nx
J. Am. Chem. Soc.
Novel MOF-derived Co@N-C bifunctional catalysts for highly efficient Zn–Air batteries and water splitting
Adv. Mater.
Hollow nitrogen-doped carbon spheres with Fe3O4 nanoparticles encapsulated as a highly active oxygen-reduction catalyst
ACS Appl. Mater. Interfaces
Metallic Co2C: a promising cocatalyst to boost photocatalytic hydrogen evolution of colloidal quantum dots
ACS Catal.
Hollow Multivoid nanocuboids derived from ternary Ni–Co–Fe Prussian blue analog for dual-electrocatalysis of oxygen and hydrogen evolution reactions
Adv. Funct. Mater.
Transforming nickel hydroxide into 3D Prussian blue analogue array to obtain Ni2P/Fe2P for efficient hydrogen evolution reaction
Adv. Energy Mater.
Cited by (98)
Heterometallic macromolecules: Synthesis, properties and multiple nanomaterial applications
2024, Coordination Chemistry ReviewsRecent progress in transition metal carbides and nitrides based composites as bifunctional oxygen electrocatalyst for zinc air batteries
2023, Journal of Alloys and Compounds