A simple preparation of Co0.75Fe0.25 hydrous oxide nanoparticles as active electrocatalysts for water oxidation reaction

A serious of CoFe hydrous oxide nanoparticles (Co_1?zFe_zO_xH_y NP z = 0-1]) were synthesized by stirring CoCl₂ and FeCl₂ in aqueous KOH solutions for 0.5 hours, and the resulting nanoparticles are active electrocatalysts for water oxidation reaction (WOR) in alkaline solutions. The Co_0.75Fe_0.25O_xH_y NP, which are the most active electrocatalysts, have a layered double hydroxide (LDH) structure, with the average particle sizes about 16 nm. When using Ni foam as the substrate, the electrode with Co_0.75Fe_0.25O_xH_y NP as catalysts exhibited an overpotential of 284 mV for WOR in 1 M KOH at 10 mA cm^?2. The Tafel slope was 43 mV dec^?1, and the TOF was 1.30 s^?1 at 350 mV overpotential (loading Co + Fe = 0.133 mg cm^?2). The Co_0.75Fe_0.25O_xH_y NP are robust toward long-term galvanostatic test and showed less than 2% dissolution in 10 hours. Preliminary kinetic study suggests that the presence of Fe in Co_1?zFe_zO_xH_y NP alters the WOR mechanistic pathways. The increased number of electrochemically active sites endowed by the LDH structure and the electronic interactions between Co and Fe as suggested by XPS, both contribute to the enhanced WOR activity.