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Nature Communications, Published online: 25 October 2022; doi:10.1038/s41467-022-34062-6

For relaxor ferroelectrics, correlating their properties and local structures is challenging. Here, the authors correlate the atomic-scale structure and the large dynamic electromechanical property in Bi0.5Na0.5TiO3-based relaxor ferroelectrics.

A flexible free-standing bifunctional electrode (N₂-NiFe-PBA/NCF/CC-60) is constructed by the 3D spatial combination of CN vacancy-mediated NiFe-PBA and N-doped carbon nanofibers rooted on carbon cloth. The N₂-NiFe-PBA/NCF/CC-60 electrode delivers high-efficiency and stabilized bifunctional oxygen reduction and oxygen evolution reaction catalytic performance. Furthermore, the N₂-NiFe-PBA/NCF/CC-60 based Zn–air battery operates 2000 discharge/charge cycles.

Abstract

Constructing flexible free-standing electrodes with efficient bifunctional performance is significant for improving the performance of flexible Zinc–air batteries. Herein, a flexible free-standing bifunctional electrode (N₂-NiFe-PBA/NCF/CC-60) is constructed by the 3D spatial combination of CN vacancy-mediated NiFe Prussian Blue Analogue (NiFe-PBA) and N-doped carbon nanofibers (NCF) rooted on carbon cloth (CC). The in situ formed CN vacancies by N₂-plasma activation tune the local coordination environment and electronic structure of Ni-Fe active sites in NiFe-PBA, thus improving the oxygen evolution reaction (OER) catalytic intrinsic activity, and restraining the loss of Fe element during OER process. The combination of NiFe-PBA and NCF presents a 3D interworking network structure, which exhibits a large specific surface and excellent electrical conductivity, thus guaranteeing sufficient, stable, and efficient oxygen reduction reaction (ORR)/OER active sites. Therefore, the N₂-NiFe-PBA/NCF/CC-60 electrode delivers high-efficiency OER activity with a low overpotential (270 mV at 50 mA cm⁻²) and excellent ORR performance with a positive potential of 0.89 V at 5 mA cm⁻². The N₂-NiFe-PBA/NCF/CC-60 based Zn–air batteries display outstanding discharge/charge stability for 2000 cycles. Meanwhile, the corresponding flexible Zn–air batteries with satisfactory mechanical properties exhibit a low voltage gap of 0.52 V at 1.0 mA cm⁻².