3D Spatial Combination of CN Vacancy‐Mediated NiFe‐PBA with N‐Doped Carbon Nanofibers Network Toward Free‐Standing Bifunctional Electrode for Zn–Air Batteries

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 .