Characterization of sulfur layers from reduced sulfur dioxide on porous platinum black/teflon electrodes

Abstract Sulfur layers related to those which modify catalytic activity have been deposited on porous platinum black/polytetrafluoroethylene electrodes through reduction of sulfur dioxide previously adsorbed from SO 2 -containing aqueous sulfuric acid solutions. These layers were controlled and modified by various electrode pretreatments and then studied using voltammetry and coulometry. Evidence is presented for the existence of at least two types of adsorbed SO 2 on the platinum black, corresponding to strongly- and weakly-bound species, and for the oxidative removal of adsorbed SO 2 by reaction with oxygen dissolved in the H 2 SO 4 pretreatment solutions. Different types of derived sulfur also are obtained. This derived sulfur apparently reflects the nature of the adsorbed SO 2 layer from which it is obtained. The various adsorbed states are discussed in terms of bilayer formation, electrode surface roughness and possible sulfur-induced faceting of the platinum black electrode.