Hollow Tubular Structure of NiCo2S4/NiFe‐LDH can Function as a Bifunctional Catalyst for Aqueous and Flexible Zinc‐Air Batteries

The hollow tubular NiCo₂S₄/NiFe-(LDH) layered double hydroxide was successfully synthesized through a sulfurization process, exhibiting an exceptional oxygen evolution reaction potential of 1.55 V at 10 mA cm⁻² and an oxygen reduction reaction half-wave potential of 0.80 V. As an air cathode in Zn-air batteries, it demonstrated excellent cycling stability (450 h) at 3 mA cm⁻².

This work initially prepares 1D hollow rod-like NiCo₂S₄ nanomaterials using the solvothermal method, and subsequently grew NiFe- layered double hydroxide (LDH) nanosheets on their surface, thereby obtaining NiCo₂S₄/NiFe-LDH composite materials. The uniform dispersion and growth of the sheet-like NiFe-LDH on the surface of the NiCo₂S₄ nanorods effectively maintained structural stability during the catalytic process, thus achieving efficient and stable catalytic performance. Additionally, the hollow NiCo₂S₄ nanorods maximize the exposure of active sites, thereby exhibiting excellent oxygen reduction reaction (ORR) performance. Meanwhile, the sheet-like NiFe-LDH grown on the surface of the NiCo₂S₄ nanorods demonstrates excellent oxygen evolution reaction (OER) activity. Furthermore, NiCo₂S₄/NiFe-LDH exhibits excellent bifunctional catalytic activity for both ORR and OER (ΔE = 0.75 V). The overpotential of the OER is 320mv and the half-wave potential of the ORR is 0.80 V. The catalyst was used as a cathode material for zinc-air batteries. When tested at a current density of 3 mA cm⁻², the charge/discharge cycle can be stabilized for ≈450 h. When tested at a current density of 5 mA cm⁻², the battery was able to maintain stable charge/discharge cycling for ≈350 h.

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