In situ free-surfactant synthesis and ORR-Electrochemistry of carbon-supported Co3S4 and CoSe2 nanoparticles

Carbon-supported Co3S4 and CoSe2 nanoparticles were synthesized by a direct reaction of monodispersive cobalt nanoparticles with sulfur powder under mild conditions without any surfactant preventing particle aggregation. The surfactants were difficult to completely remove from the particles after synthesis, which influenced the electrochemical and magnetic properties of these nanoparticles. Co3S4/C-01 was obtained by decomposition of Co2(CO)8 in the mixture solution containing the surfactants such as oleic acid and TOPO at the refluxing temperature followed by the reaction between cobalt particles and sulfur and then deposited on the carbon. Co3S4/C-02 and 03 without surfactant show higher activity toward ORR with an OCP of between 0.66 and 0.68 V vs RHE and higher current densities than Co3S4-01 with the surfactants.