Influence of carbon surface pre-oxidation on the properties of silver + carbon electrocatalysts

Abstract

The influence of oxygen-containing groups of the carbon surface on the properties of metal + carbon catalysts was studied by using pre-oxidized carbon as a support for an Ag + C catalyst. The Ag particle size distribution and Ag crystal structure were examined by high resolution transmission electron microscopy. The catalytic activity of the catalysts for oxygen reduction was measured using a soft-embedded microelectrode and a soft-embedded rotating disk electrode. Results showed that the pre-oxidation of carbon is favourable for increasing metal dispersion; however, the interaction between Ag particles and the carbon surface was weakened, and the fine particles floated off from the carbon surface easily. The formation of Ag crystallites becomes more difficult on a pre-oxidized carbon surface, and in the extreme yields amorphous particles. Oxygen reduction on an Ag particle surface is a structure-sensitive reaction; the catalytic activity of Ag particles for this reaction is not proportional to the degree of metal dispersion: on those Ag particle surfaces formed by the interaction of metal precursor with the surface oxygen-containing groups, the four-electron reduction was enhanced, whereas on those formed using the functional ion pre-adsorption method, the two-electron reduction of oxygen was favoured.