The research of new water electrolysis catalysts: Co(OH)x-NiFeP/NF

Developing efficient and durable bifunctional catalysts for water electrolysis under high current densities (HCD) is essential for sustainable energy systems. This research synthesized a hierarchical Co(OH)x-NiFeP/NF catalyst with a crystalline-amorphous interface via electrochemical deposition. Scanning and transmission electron microscopy (SEM/TEM) revealed a unique nanostructure characterized by nanoneedles coated with amorphous Co(OH)x, optimizing surface roughness and active site exposure. Electrochemical measurements demonstrated outstanding OER performance, the overpotential of Co(OH)x-NiFeP/NF achieving 285 mV at 200 mA cm⁻² and 357 mV at 1000 mA cm⁻², significantly outperforming NiFeP/NF and Co(OH)x/NF. The catalyst exhibited a low Tafel slope (84 mV dec⁻¹) and superior intrinsic activity with a turnover frequency (TOF) of 0.87 s⁻¹ at 300 mV. Furthermore, EIS results indicated minimal charge transfer resistance (1.185 Ω), and durability testing confirmed stable operation over 200 hours at high current densities. Co(OH)x-NiFeP/NF also performs well when integrated into a complete water-splitting system, surpassing most reported bifunctional catalysts. This work demonstrates the potential of Co(OH)x-NiFeP/NF as an economically benefit and resizable catalyst for high-performance water electrolysis.