Searching for high-quality air electrode catalysts is the long-term goal for the practical application of Zn-air batteries. Here, a series of coexistent composite materials (CoNi/NHCS-TUC-x) of cobalt-nickel supported on nitrogen-doped hollow spherical carbon and tubular carbon are obtained using a simple pyrolysis strategy. Co and Ni in the composites are mainly present in the form of alloy nanoparticles, M-Nx and M-Cx (M = Co or Ni) species, with high oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) electroactivity. The materials containing different proportions of spherical carbon and tubular carbon obtained by simply adjusting the raw materials for generating tubular carbon exhibit interesting bifunctional performance: samples with an abundant tubular content have the highest ORR onset potential (0.91 V vs reversible hydrogen electrode), while those with a rich spherical content have the highest ORR current density (5.13 mA·cm-2). Furthermore, CoNi/NHCS-TUC-3 provides the lowest potential difference (ΔE = Ej=10 - E1/2) of 0.806 V. We then test the potential possibility of CoNi/NHCS-TUC-3 as an air electrode for primary and rechargeable Zn-air batteries. The primary battery delivers an open-circuit potential of 1.59 V, a peak power density of 361.8 mA·cm-2, and a specific capacity of 756.5 mA h·gZn-1. The rechargeable battery could be cycled stably for more than 55 h at 10 mA·cm-2. These characteristics make CoNi/NHCS-TUC-3 a superior electrocatalyst for both the ORR and OER, as well as a suitable bifunctional electrode applied to a rechargeable Zn-air battery.

CoNi Nanoparticles Supported on N-Doped Bifunctional Hollow Carbon Composites as High-Performance ORR/OER Catalysts for Rechargeable Zn-Air Batteries.

The fossil-fuel shortage and severe environmental issues have posed ever-increasing demands on clean and renewable energy sources, for which the exploration of electrocatalysts has been in a big challenge toward...

Process of metal−organic framework (MOF)/covalent−organic framework (COF) hybrids-based derivatives and their applications on energy transfer and storage

Ce-doped ZIF-67 derived Co3O4 nanoparticles supported by carbon nanofibers: A synergistic strategy towards bifunctional oxygen electrocatalysis and Zn-Air batteries

The ability to craft high-efficiency and non-precious bifunctional oxygen catalysts opens an enticing avenue for the real-world implementation of metal-air batteries (MABs). Herein, Co3 O4 encapsulated within nitrogen defect-rich g-C3 N4 (denoted Co3 O4 @ND-CN) as a bifunctional oxygen catalyst for MABs is prepared by graphitizing the zeolitic imidazolate framework (ZIF)-67@ND-CN. Co3 O4 @ND-CN possesses superb bifunctional catalytic performance, which facilitates the construction of high-performance MABs. Concretely, the rechargeable zinc-air battery based on Co3 O4 @ND-CN shows a superior round-trip efficiency of ≈60% with long-term durability (over 340 cycles), exceeding the battery with the state-of-the-art noble metals. The corresponding lithium-oxygen battery using Co3 O4 @ND-CN exhibits an excellent maximum discharge/charge capacity (9838.8/9657.6 mAh g-1 ), an impressive discharge/charge overpotential (1.14 V/0.18 V), and outstanding cycling stability. Such compelling electrocatalytic processes and device performances of Co3 O4 @ND-CN originate from concurrent compositional (i.e., defect-engineering) and structural (i.e., wrinkled morphology with abundant porosity) elaboration as well as the well-defined synergy between Co3 O4 and ND-CN, which produce an advantageous surface electronic environment corroborated by theoretical modeling. By extension, a rich diversity of other metal oxides@ND-CN with adjustable defects, architecture, and enhanced activities may be rationally designed and crafted for both scientific research on catalytic properties and technological development in renewable energy conversion and storage systems.

Defect-Engineered Co3 O4 @Nitrogen-Deficient Graphitic Carbon Nitride as an Efficient Bifunctional Electrocatalyst for High-Performance Metal-Air Batteries.

Transition metal-nitrogen-carbon (TM-N-C) nanomaterials are promising platinum-based substitutes for the oxygen reduction reaction (ORR). However, large-scale commercial production of high-efficiency, durable TM-N-C catalysts remains a formidable challenge. In this work, a facile ″ZIF-on-ZIF″ strategy is first adopted to design ZIF-8@ZIF-67 core-shell polyhedral nanocages, and then, ferrocene (Fc) is added to form ZIF-8@ZIF-67@Fc double-layer encapsulating polyhedral nanocages. Finally, Zn, Co, and Fe tridoped N-C nanocages (ZnCoFe-N-C) as the high-efficiency ORR electrocatalyst are prepared through high-temperature annealing. Benefiting from the trimetal, nitrogen and carbon species bond to each other to form highly efficient active sites, and the material exhibits outstanding performance in 0.1 M KOH, onset potential and half-wave potential of up to 0.95 and 0.878 V (vs RHE), respectively, and long-term durability and methanol tolerance. Furthermore, when utilizing as a zinc-air battery (ZAB) air electrode, it exhibits wonderful indicators, reflected in an open circuit voltage of 1.525 V, power density of 350.2 mW cm-2, and specific capacity of 794.7 mAh gzn-1, which outperforms the benchmark Pt/C catalyst. This work provides a facile and effective strategy to obtain a highly efficient and stable TM-N-C electrocatalyst for the ORR in ZABs.

Zn, Co, and Fe Tridoped N-C Core-Shell Nanocages as the High-Efficiency Oxygen Reduction Reaction Electrocatalyst in Zinc-Air Batteries.

Heteroatom functionalized double-layer carbon nanocages as highly efficient oxygen electrocatalyst for Zn-Air batteries

Looking for a high-efficiency, durabile, and low-cost dual-functional oxygen electrocatalyst as the air electrode catalyst in rechargeable zinc-air batteries (ZABs) is urgently desirable but faces many challenges. Herein, we propose the preparation strategy of effectively using a bifunctional electrocatalyst (Fe-Nx/C) based on the zeolite imidazole organic framework-8 (ZIF-8) as the template agent, with surface modification coated by ferrocene (Fc) molecules followed by pyrolysis at high temperature under inert atmosphere. Benefiting from the surface modification of ZIF-8 with Fc molecules, more abundant multiple catalytic Fe/Fe-Nx/FeCx sites with high intrinsic activity are derived, the resultant Fe-Nx/C exhibits excellent potential gap (ΔE = 0.63 V) and durability, which is obviously superior to the Pt/C + IrO2 benchmark (ΔE = 0.77 V) and other state-of-the-art electrocatalysts. Furthermore, the assembled rechargeable ZABs employing the Fe-Nx/C as an air-electrode show a reduced charging-discharging potential difference of 0.603 V, high power density of 214.8 mW cm-2, and long-term cycling stability of more than 290 h at 2.0 mA cm-2. Therefore, this work presents a feasible strategy to prepare a high-efficiency and durability ORR/OER bifunctional electrocatalyst toward high performance ZABs and next-generation energy storage devices.

Guang Li

Papers

Zn, Co, and Fe Tridoped N-C Core-Shell Nanocages as the High-Efficiency Oxygen Reduction Reaction Electrocatalyst in Zinc-Air Batteries.

Heteroatom functionalized double-layer carbon nanocages as highly efficient oxygen electrocatalyst for Zn-Air batteries

Design and Facile Synthesis of Highly Efficient and Durable Bifunctional Oxygen Electrocatalyst Fe-Nx/C Nanocages for Rechargeable Zinc-Air Batteries.