Ternary Nickel-Iron-Phosphorus (NiFeP) Electrocatalysts for Alkaline Water Splitting

In this study, ternary NiFeP coatings were fabricated on a copper substrate using a simple, fast, and cost-effective electroless deposition method. The coatings were named Ni₈₅Fe₄P₁₂, Ni₈₀Fe₈P₁₂, and Ni₇₅Fe₁₂P₁₂, indicating 4, 8, and 12 at % of Fe, respectively. The surface morphology and composition of the coatings were characterized using scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). The activity of the prepared coatings was evaluated using the water-splitting reaction to determine the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in a 1 M KOH electrolyte solution. Electrochemical measurements were carried out in a temperature range from 25 °C to 55 °C. The HER and OER current density values increased by up to 2.58 and 2.13 times, respectively, with temperature increase compared to the result at 25 °C. All three coatings demonstrated activity in both reactions. Ni₈₅Fe₄P₁₂ exhibited the highest catalytic efficiency in the HER, with the overpotential of 340 mV at 10 mAcm⁻² and a Tafel slope of 61 mVdec⁻¹. In the OER, the efficiency of the NiFeP catalysts correlated with their Fe content. The overpotential was 412 mV for Ni₈₀Fe₈P₁₂ and 432 mV for Ni₇₅Fe₁₂P₁₂ at 10 mAcm⁻² with Tafel slopes of 96 and 91 mVdec⁻¹, respectively. This study underscores the critical influence of Fe content on the catalytic efficiency of NiFeP coatings, with reduced Fe content enhancing HER and increased Fe content benefits OER.