Cobalt–iron layered double hydroxide nanosheet-wrapped nitrogen-doped graphite felt as an oxygen-evolving electrode

Abstract

The electrocatalytic performance of cobalt–iron layered double hydroxide (CoFe-LDH) nanosheets is enhanced by growing them in situ on N-doped graphite felt using a solvothermal route. The effects of different parameters including solvent, temperature and reaction time are investigated. Pure CoFe-LDH nanosheets are obtained using methanol as a solvent at the optimum temperature (130 °C) and reaction time (18 hours) while metal (Fe and Co) oxides are formed in a hydrothermal process. The CoFe-LDH@NGF (130 °C, 18 h) displays enhanced catalytic performance and stability for the oxygen evolution reaction (OER) in alkaline media and produces a current density of 10 mA cm⁻² at a low overpotential (220 mV), Tafel slope of 121 mV dec⁻¹, charge transfer resistance of 1.48 Ω, high exchange current density and double layer capacitance of 226.65 mF cm⁻². The OER activity of the CoFe-LDH@NGF electrode exceeds that of pristine CoFe-LDH, conventional RuO₂, and other CoFe-LDH-based electrocatalysts reported in the literature. Thus, the CoFe-LDH@NGF electrode is a potential alternative to expensive noble metals (Ru, Ir) and other transition metal-based electrocatalysts for commercial alkaline water splitting. Moreover, the current synthesis approach can be employed to make other layered double hydroxide-based electrodes for electrochemical applications.