Spherical Rh17S15@C and Rh@C core–shell nanocomposites: Synthesis, growth mechanism and methanol tolerance in oxygen reduction reaction

Abstract

Core–shell structured Rh17S15@C and Rh@C nanocomposites have been synthesized by a one-step solvothermal method from the reaction of Rh6(CO)16 with or without sulfur in acetone. The resultant Rh17S15@C composite consists of spherical Rh17S15 cores with homogeneous diameter of ∼20nm and amorphous carbon shell of 11–15nm in thickness. The sulfide core and the carbon shell are tunable in size through adjusting the acetone concentration or altering the solvothermal reaction time respectively. N2 adsorption–desorption measurement suggests that the composite is porous with relative high surface area over 180m2g−1. In the absence of sulfur, Rh@C composite was prepared by the same method. This composite is of similar core–shell structure as that of the sulfur-contained product with metallic Rh nanospheres as cores. The role of acetone in the preparation of those composites was found to be triplex. As solvent it provides the solvothermal environment, and most importantly it participates in the formation of the spherical cores and is the source of the carbon shell. Cyclic voltammetry and rotating disk electrode measurements were employed to evaluate the electrocatalytic activity of these composites for oxygen reduction reaction in the presence and absence of methanol.