作者：任丁 材料学院

指导老师：张强 化工系

关键词：锌-空气电池 高性能 双功能 不对称正极

摘要

Zinc–air batteries deliver great potential as emerging energy storage systems but suffer from sluggish kinetics of the cathode oxygen redox reactions that render unsatisfactory cycling lifespan. The exploration on bifunctional electrocatalysts for oxygen reduction and evolution constitutes a key solution, where rational design strategies to integrate various active sites into a high-performance air cathode remain insufcient. Herein, a multiscale construction strategy is proposed to rationally direct the fabrication of bifunctional oxygen electrocatalysts for long-lifespan rechargeable zinc–air batteries. NiFe layered double hydroxides and cobalt coordinated framework porphyrin are selected as the active sites considering their high intrinsic activity at the molecular level, and the active sites are successively integrated on three-dimensional conductive scaffolds at mesoscale to strengthen ion transportation. Consequently, the multiscale constructed electrocatalyst exhibits excellent bifunctional performance (ΔE = 0.68 V), which is even better than that of the noble metal based benchmarks. The corresponding air cathodes endow zinc–air batteries with a reduced voltage gap of 0.74 V, a high power density of 185.0 mW cm-2, and an ultralong lifespan of more than 2400 cycles at 5.0 mA cm-2. This work demonstrates a feasible strategy to rationally integrate various active sites to construct multifunctional electrocatalysts for energy-related processes.

Synthesis and Characterization

Characterizations of LDH-POF. a) SEM, b) tTEM, and c) HAADF-STEM and corresponding EDS elemental mapping images of LDH-POF. d) Elemental analysis based on ICP-OES of LDH-POF, POF, and LDH. e) High-resolution HAADF-STEM image of LDH-POF, the inset is the linear scan analysis along the arrow. f) XRD patterns of LDH-POF and LDH.

Bifunctional electrochemical test

Electrocatalytic bifunctional performance evaluation. a) Bifunctional LSV curves of the LDH-POF and Pt/C+Ir/C electrocatalysts tested in O2-saturated 0.10 m KOH electrolyte and b) corresponding Tafel plots. c) Diagram for comparing the bifunctional electrocatalytic performance of LDHPOF, Pt/C+Ir/C, and other reported noble-metal-free electrocatalysts.

Zinc-air battery test

Performances of rechargeable zinc–air batteries. a) Charge and discharge polarization profles and discharge power density and b) rate performances of the LDH-POF and Pt/C+Ir/C cathodes. Galvanostatic cycling curves at c) 5.0 mA cm-2 of the LDH-POF cathodes and d) 25 mA cm-2 of the LDH-POF and Pt/C+Ir/C cathodes.

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