The influence of reaction temperature and surfactant on the magnetic and catalytic properties of FeCo nanoparticles

Abstract FeCo nanoparticles were prepared by controlling the reaction temperature and addition of surfactant. With the increasing of reaction temperature, CoFe2O4 impurities disappeared and crystalline FeCo nanoparticles were got. High Ms of 218.5 emu/g and low Hc of 90.2 Oe were observed after reacting at 150 oC. The best OER (oxygen evolution reaction) properties with low onset potential (0.73 V) and small Tafel value (105 mV/dec) were found in FeCo nanoparticles prepared at 150 oC. With increasing the surfactant ratio, the purity of FeCo particles did not change. However, the repulsive forces between the polar ends of oleic acid molecules induced the formation of uniform small FeCo nanoparticles. Large Ms of 166.4 emu/g and small Hc of 75.0 Oe were observed when the surfactant ratio was 3:1. The best OER activity with low onset potential (0.63 V) and small Tafel value (67 mV/dec) were found in FeCo nanoparticles prepared with the surfactant ratio of 3:1. The improved OER activity was contributed to the impurity reduction, the better crystallization, the larger surface area and the better magnetic properties, which could provide small electric resistance, more active sites and easy electron transfer.