Abstract:

To circumvent the cost constraints and scarcity of noble-metal oxygen evolution reaction (OER) catalysts, this work pioneers an electrolyte-regulation strategy for boosting nickel phosphide (Ni₂P) performance. Introducing a trace amount of Co²⁺ (40 µL 1 M CoSO₄) into the alkaline KOH electrolyte significantly enhances the surface adsorption kinetics and reactivity of Ni₂P. The optimized system achieves a reduction in overpotential to 363.9 mV, a decrease in Tafel slope to 109.6 mV dec⁻¹, and a smaller charge transfer resistance. Mechanism research reveals that a dynamic "oxidation-adsorption-reconstruction" process is driven by electrical oxidation. Specifically, Co²⁺ undergoes an oxidation reaction and is adsorbed on the material surface, leading to the in-situ formation of an epitaxial CoOOH/NiOOH heterointerface. This simultaneously increases active-site density, optimizes OH* adsorption energy, and accelerates interfacial electron transfer. This electrolyte-catalyst synergy strategy redefines efficient OER electrocatalyst design, shifting focus from complex material engineering to intelligent interfacial microenvironment control.

Key words: Oxygen evolution reaction, Nickel phosphide, Cobalt ion, Surface reconstruction, Adsorption energy