Investigation of methanol electrooxidation on Au/C catalyst in alkaline medium

Gold nanoparticles supported on activated carbon (Au/C) are prepared by rapid reduction with KBH₄, after AuCl4- was partially deposited on the surface of the activated carbon by the reaction of AuCl4- and ammonia. Through the characterization of the transmission electron microscope and X-ray powder diffraction, the mean diameter of the Au nanoparticles (AuNPs) decreases with the increase of the Au loading. The energy dispersive X-ray spectroscopy analysis is carried out for measuring the Au loadings of the Au/C catalysts. The results exhibit the Au/C catalyst with 20 wt% Au has the highest loading efficiency (94.5%). The origin of the catalytic activity of Au/C catalysts for the methanol electrooxidation (MEO) is investigated by the cyclic voltammetry, which indicates that the current densities normalized by the actual Au loading for the MEO increase with a decrease in the mean diameter of AuNPs by a factor of 2.42-3.17. Based on this result, the active sites (corners, edges and step sites) for the MEO are proposed.