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Abstract It is essential but still challenging to design and construct inexpensive, highly active bifunctional oxygen electrocatalysts for the development of high power density zinc–air batteries (ZABs). Herein, a CoFe‐S@3D‐S‐NCNT electrocatalyst with a 3D hierarchical structure of carbon nanotubes growing on leaf‐like carbon microplates is designed and prepared through chemical vapour deposition pyrolysis of CoFe‐MOF and subsequent hydrothermal sulfurization. Its 3D hierarchical structure shows excellent hydrophobicity, which facilitates the diffusion of oxygen and thus accelerates the oxygen reduction reaction (ORR) kinetic process. Alloying and sulfurization strategies obviously enrich the catalytic species in the catalyst, including cobalt or cobalt ferroalloy sulfides, their heterojunction, core–shell structure, and S, N‐doped carbon, which simultaneously improve the ORR/OER catalytic activity with a small potential gap (ΔE = 0.71 V). Benefiting from these characteristics, the corresponding liquid ZABs show high peak power density (223 mW cm−2), superior specific capacity (815 mA h gZn−1), and excellent stability at 5 mA cm−2for ≈900 h. The quasi‐solid‐state ZABs also exhibit a very high peak power density of 490 mW cm−2and an excellent voltage round‐trip efficiency of more than 64%. This work highlights that simultaneous composition optimization and microstructure design of catalysts can effectively improve the performance of ZABs.
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Doping-modulated strain control of bifunctional electrocatalysis for rechargeable zinc–air batteries
Changes in the local atomic arrangement in a crystal caused by lattice-mismatch-induced strain can efficiently regulate the performance of electrocatalysts for zinc–air batteries (ZABs) in many manners, mainly due to modulated electronic structure configurations that affect the adsorption energies for oxygen-intermediates formed during oxygen reduction and evolution reactions (ORR and OER). However, the application of strain engineering in electrocatalysis has been limited by the strain relaxation caused by structural instability such as dissolution and destruction, leading to insufficient durability towards the ORR/OER. Herein, we propose a doping strategy to modulate the phase transition and formation of self-supported cobalt fluoride–sulfide (CoFS) nanoporous films using a low amount of copper (Cu) as a dopant. This well-defined Cu–CoFS heterostructure overcomes the obstacle of structural instability. Our study of the proposed Cu–CoFS also helps establish the structure–property relationship of strained electrocatalysts by unraveling the role of local strain in regulating the electronic structure of the catalyst. As a proof-of-concept, the Cu–CoFS electrocatalyst with doping-modulated strain exhibited superior onset potentials of 0.91 V and 1.49 V for the ORR and OER, respectively, surpassing commercial Pt/C@RuO 2 and benchmarking non-platinum group metal (non-PGM) catalysts. ZABs with the Cu–CoFS catalyst delivered excellent charge/discharge cycling performance with an extremely low voltage gap of 0.5 V at a current density of 10 mA cm −2 and successively 0.93 V at a high current density of 100 mA cm −2 and afforded an outstanding peak power density of 255 mW cm −2 .
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- PAR ID:
- 10288228
- Date Published:
- Journal Name:
- Energy & Environmental Science
- ISSN:
- 1754-5692
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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null (Ed.)Iron single atom catalysts have emerged as one of the most active electrocatalysts towards the oxygen reduction reaction (ORR), but the unsatisfactory durability and limited activity for the oxygen evolution reaction (OER) has hampered their commercial applications in rechargeable metal–air batteries. By contrast, cobalt-based catalysts are known to afford excellent ORR stability and OER activity, due to the weak Fenton reaction and low OER Gibbs free energy. Herein, a bimetal hydrogel template is used to prepare carbon aerogels containing Fe–Co bimetal sites (NCAG/Fe–Co) as bifunctional electrocatalysts towards both ORR and OER, with enhanced activity and stability, as compared to the monometal counterparts. High-resolution transmission electron microscopy, elemental mapping and X-ray photoelectron spectroscopy measurements demonstrate homogeneous distributions of the metal centers within defected carbon lattices by coordination to nitrogen dopants. X-ray absorption spectroscopic measurements, in combination with other results, suggest the formation of FeN 3 and CoN 3 moieties on mutually orthogonal planes with a direct Fe–Co bonding interaction. Electrochemical measurements show that NCAG/Fe–Co delivers a small ORR/OER potential gap of only 0.64 V at the current density of 10 mA cm −2 , 60 mV lower than that (0.70 V) with commercial Pt/C and RuO 2 catalysts. When applied in a flexible Zn–air battery, the dual-metal NCAG/Fe–Co catalyst also shows a remarkable performance, with a high open-circuit voltage of 1.47 V, a maximum power density of 117 mW cm −2 , as well as good rechargeability and flexibility. Results from this study may offer an ingenious protocol in the design and engineering of highly efficient and durable bifunctional electrocatalysts based on dual metal-doped carbons.more » « less
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/D1EE01271A
