Mo-doping directed nanoflower architecture in NiFe phosphide for ultralow-overpotential oxygen evolution catalysis

Abstract

Developing efficient and stable oxygen evolution reaction (OER) electrocatalysts is crucial for advancing industrial-scale hydrogen production. To address the limitations of insufficient active sites and sluggish kinetics in transition metal phosphides (TMPs), we report a three-dimensional hierarchical Mo_0.6Ni_1.05Fe_0.15P/NF nanoflower electrocatalyst fabricated on nickel foam (NF) via stepwise hydrothermal-phosphidation. Synergistic Mo doping critically guides the formation of the nanoflower morphology, yielding a high specific surface area of 59.31 m² g⁻¹ and abundant edge active sites. This unique architecture, combined with optimized Mo-Fe-Ni electronic interactions that lower the charge transfer resistance to 4.3 Ω, enables exceptional OER performance in 1 M KOH: remarkably low overpotentials of 176, 263, and 351 mV at 10, 50, and 100 mA cm⁻², respectively. These values surpass most reported TMP-based catalysts and rival commercial RuO₂. Furthermore, the catalyst demonstrates robust stability, maintaining 80 % current density after 48 h of operation. Our work establishes that morphology-composition modulation via high-valent Mo doping effectively enhances active site exposure, optimizes OH⁻ adsorption energetics, and accelerates charge transfer kinetics. This study provides fundamental insights into multi-metallic phosphide design and demonstrates a high-performance, non-precious alternative for practical water electrolysis.