Fundamental Aspects of ad-Metal Dissolution and Contamination in Low and Medium Temperature Fuel Cell Electrocatalysis: A Cu Based Case Study Using In Situ Electrochemical X-ray Absorption Spectroscopy

Abstract

Electrochemical methods (cyclic voltammetry and rotating ring disk electrode) and in situ X-ray absorption spectroscopy (XAS) were used in conjunction to study copper adsorption onto carbon-supported platinum nanoparticles over the operating potential range of proton exchange membrane fuel cell (PEMFC) cathodes and anodes (∼0.0–1.0 V vs the reference hydrogen electrode, RHE). Our purpose was to better understand the detrimental effects of Cu leaching from high-activity dealloyed PtCux electrocatalysts. These studies were conducted in CuSO4-doped 0.1 N solutions of HClO4 and H2SO4 under both inert and oxygenated conditions. Over the anode potential range (∼0.0–0.3 V vs RHE), concentrations of Cu2+ as low as 10 μM were found to coat the active Pt surfaces, thereby drastically inhibiting the hydrogen oxidation reaction. Over the Cu underpotential deposition region (0.35–0.70 V vs RHE), Cu2+ concentrations ≥0.05 mM resulted in Cu deposition onto Pt. This was found to lower the oxygen reduction reaction activi...