Decoration NiFe layered double hydroxide on nitrogen doped carbon nanotube confined Fe nanoparticles for superior rechargeable zinc air battery

Abstract

The bifunctionality of oxygen electrocatalyst for rechargeable zinc air battery (ZAB) strongly determines the performance and stability. In this study, we devise the formation of nickel-iron layered double hydroxide (NiFe-LDH) decorated nitrogen doped carbon nanotubes confined iron nanoparticles (NiFe-LDH@Fe/NCNT) as superior electrocatalyst for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The overpotential at 10 mA cm⁻² is 264 mV for NiFe-LDH@Fe/NCNT, 49 mV lower than commercial IrO₂, corresponding to a 14.3-fold higher specific activity. A fast surface reconstruction to active site is found for NiFe-LDH@Fe/NCNT from operando electrochemical impedance spectroscopy. Besides, the kinetic current density is 4.39 mA cm⁻² for NiFe-LDH@Fe/NCNT at 0.85 V vs. RHE, depicting a 1.3-time high than commercial Pt/C in ORR catalysis. The exceptional bifunctionality of NiFe-LDH@Fe/NCNT is reflected by the ΔE (E_η10-E_1/2) of 0.61 V, relatively narrower than Pt/C-IrO₂. Moreover, the ZAB performance reaches 223.3 mW cm⁻² for NiFe-LDH@Fe/NCNT, which is enhanced by a factor of 1.7 compared to Pt/C-IrO₂; additionally, stable voltage gap is recorded for NiFe-LDH@Fe/NCNT within 510 h. The all-solid-state ZAB offers a maximum power density of 104.5 mW cm⁻². The enhanced catalytic activity is originated from the electronic interaction between NiFe-LDH and Fe/NCNT contributing to an upshifted d band center, enhancing the binding strength between active site and oxygen reaction intermediates.