Simple Liquid-Phase Synthesis of Cobalt Carbide (Co<sub>2</sub>C) Nanoparticles and Their Use as Durable Electrocatalysts

Cobalt carbide (Co2C) nanoparticles were synthesized simply in liquid phase using Co(II) acetylacetonate and oleylamine under reflux conditions. Even in the presence of carbon black XC-72, Co2C nanoparticles were formed and simultaneously deposited on the carbon surface. The thin layer consisting of cobalt (oxy)hydroxide was present on the outermost surface of the thus-prepared Co2C nanoparticles, which was confirmed by X-ray photoelectron spectroscopy, but the redox treatment using a cyclic voltammetry technique gradually removed such by-product phase. The resulting Co2C nanoparticles supported on XC-72 exhibited high durability for the oxygen reduction reaction.