One-step preparation of amorphous citrate-chelated CoNiFe trimetallic hydroxides for the oxygen evolution reaction†

Reasonable morphology regulation and electronic structure modulation enhance the oxygen evolution reaction (OER) performance of the catalyst. In this study, amorphous citrate-chelated CoNiFe trimetallic hydroxide nanoparticles were synthesized in one step via coprecipitation at room temperature. The choice of solvents controlled the hydrolysis rate of metal cations, allowing for the regulation of the product morphology. An alcohol–water system as the solvent facilitated the formation of more uniform and well-dispersed nanoparticles. Citrate was employed as a chelating agent, and its strong interaction with metal cations improved the stability of the amorphous materials, regulated the particle size, and increased the electrochemically active surface area. Furthermore, varying amounts of Ni ions were doped to modulate the electronic structure, exerting tri-metallic synergistic effects, which enhanced the OER performance. The results demonstrated that, in 1.0 M KOH, the optimized Co : Ni : Fe molar ratio of 2 : 1 : 1 achieved the highest OER activity, with an overpotential of 287 mV and a Tafel slope of 56.3 mV dec⁻¹, delivering a current density of 10 mA cm⁻², and maintaining stable performance over 24 hours with only a minor increase in the overpotential.