Mechanism of Coupled Transport in the Coarsening of Platinum under Stress in Nonaqueous Electrolyte

Abstract

Effect of mechanical stress on platinum dissolution was measured. The procedure consisted of immersing two platinum wires/foils in PtCl4 solution in DMSO. A tensile stress was applied to one of the wires/foils, while the other one was left stress-free. It was observed that wire/foil subjected to tensile stress became electrically positive, consistent with lowering of platinum chemical potential. The voltage measured varied linearly with applied stress. The measured voltage difference is in good agreement with theory. When shorted externally, the wire/foil under tensile stress thickens while the unstressed one shrinks, consistent with Pt transport from unstressed wire/foil to stressed (tensile) wire/foil. The process involves coupled transport of platinum ions through electrolyte and electrons in the external circuit. The results demonstrate the role of stress on dissolution/precipitation of Pt. Implications of the results for PEMFC catalyst degradation and the design of degradation-resistant core-shell catalysts are discussed.