Hydrogen Sulfide Poisoning of Platinum Anode in Phosphoric Acid Fuel Cell Electrolyte

Abstract

A study has been made of the effect of on the anodic oxidation of hydrogen on Pt in concentrated phosphoric acid fuel cell electrolyte over a temperature range of 25°–170°C. The anodic current vs. potential curves of a stationary Pt electrode in 94 weight percent (w/o) were measured with a half‐cell setup, and the cyclic voltammetry was used to characterize the Pt surface in the presence of . It was found that the introduction of into hydrogen gas caused a rapid decrease in the anodic current due to the adsorption of on Pt. The extent of poisoning appeared to decrease with increasing temperature and to increase with increasing potential. The cyclic voltammogram revealed that adsorbed species blocked the active sites available for the adsorption/desorption of H and thus retarded the rate of hydrogen oxidation reaction on Pt. At sufficiently high anodic potentials, a layer of adsorbed elemental sulfur formed on the electrode surface and suppressed the formation of platinum oxide at the oxygen adsorption potentials.