Abstract
Zn–air batteries (ZABs) are one of the promising power sources for portable and wearable electronic devices because of their high theoretical specific energy density and low cost. However, their practical performance with high energy density and power density is difficult to maintain under high mass-loading due to the compact restacking that seriously hinders mass/charge diffusion. Herein, we reported an efficient bi-functional electrocatalyst of Ni-Co mixed metal oxides incorporated cobalt/nitrogen doped carbon with hierarchical hollow nanostructure (H-Co/N-C@NiCo2O4). Benefiting from this structural and compositional merits, the as-synthesized H-Co/N-C@NiCo2O4 exhibits excellent electrocatalytic activity and long-term stability for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The potential gap between half-wave potential in ORR and overpotential at a current density of 10 mA cm−2 in OER reaches within 0.8 V, much smaller than that of most reported bi-functional electrocatalysts. Moreover, H-Co/N-C@NiCo2O4 is constructed as an air electrode for rechargeable ZAB, delivering a high power density and long cycling stability. A good linear relationship has been achieved between the power density and various mass-loading of H-Co/N-C@NiCo2O4 on the electrode, indicating well preserved performance even under high dense packing of catalysts, which provides a promising paradigm for the practical applications in ZAB.
Highlights
Zinc–air batteries (ZABs) have been investigated tremendously in past decades owing to their promising theoretical specific energy density of 1,086 Wh kg−1 and low cost, which would meet the ever-increasing energy requirements for renewable energy conversion devices
The good linear relationship between the power density and various mass loading of H-Co/N-C@NiCo2O4 on the electrode demonstrates that the performance has been well-maintained even under high dense packing of catalysts, which offers a new pathway for the practical applications in Zn–air batteries (ZABs)
Zeolitic imidazolate framework (ZIF-67) nanoparticles were compactly assembled on the surface of PS to obtain PS@ZIF-67 microspheres (Figures 1b, 2A)
Summary
Zinc–air batteries (ZABs) have been investigated tremendously in past decades owing to their promising theoretical specific energy density of 1,086 Wh kg−1 and low cost, which would meet the ever-increasing energy requirements for renewable energy conversion devices The good linear relationship between the power density and various mass loading of H-Co/N-C@NiCo2O4 on the electrode demonstrates that the performance has been well-maintained even under high dense packing of catalysts, which offers a new pathway for the practical applications in ZAB. For the ORR tests, the as-prepared catalyst ink was pipetted onto the rotating disk electrode (RDE, 0.196 cm2) and ring rotating disk electrode (RRDE, carbon disk with a surface area of 0.126 cm surrounded by a Pt ring with a surface area of 0.224 cm2) with a loading of 0.3 mg cm−2, and dried under room temperature. For the OER tests, the catalyst ink was pipetted onto carbon cloth with a loading of 1 mg cm−2, and dried under room temperature.
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