Ternary NiCoFe Layered Double Hydroxide Nanosheets Synthesized by Cation Exchange Reaction for Oxygen Evolution Reaction

Developing suitable catalysts which can accelerate the sluggish oxygen evolution reaction (OER) process is of high importance to fulfil the mission of hydrogen generation by water splitting. Herein, we demonstrate a facile method based on cation exchange reaction (CER) for preparation of NiCoFe layered double hydroxide (LDH) nanosheet arrays which directly grafted on flexible carbon fiber clothes (NiCoFe-LDH/CFC) for OER application. It is found that the optimal NiCoFe-LDH/CFC with 1 h CER exhibited superior OER activity than pristine NiCo-LDH material and commercial Ir/C electrode including a low onset overpotential (η) of only 240 mV and a low overpotential of 280 mV to achieve a current density of 10 mA cm⁻² in 1 M KOH electrolyte. The Tafel slope decreased from 63 mV dec⁻¹ for pristine NiCo-LDH material to 34 mV dec⁻¹ for NiCoFe-LDH/CFC with 1 h CER. At an overpotential of 0.3 V, an over 16.5 times of improvement of the turnover frequency (TOF) of NiCoFe-LDH/CFC with 1 h CER (0.0347 s⁻¹) was achieved compared to NiCo-LDH (0.0021 s⁻¹). The NiCoFe-LDH/CFC with 1 h CER demonstrated a retention rate of 98% after 10 h stability testing. All the results demonstrate the excellent electrocatalytic activity of NiCoFe-LDH/CFC for OER applications.