In Situ Analysis of Chloride Effect on Platinum Dissolution by a Channel-Flow Multi-Electrode System

The effect of Cl − on Pt dissolution under both potentiostatic and potential cycling conditions is reported, using a channel-flow multi-electrode (CFME) as an in situ detection method. To avoid the contamination of the entire CFME system by Cl−, a liquid-phase chloride ion gun is placed upstream of the double electrode. Under potentiostatic conditions, Cl − enhances Pt dissolution by forming PtCl42 − at potentials below 1.0 V and PtCl62 − above 1.2 V. Under potential cycling conditions, Cl − accelerates Pt dissolution above 1.2 V by the enhanced formation of both PtCl62 − and PtCl42−. The cathodic dissolution of Pt2+ during PtO2 reduction is also increased in the presence of Cl−. A mechanism for the effect of Cl − on Pt dissolution is proposed. © 2014 The Electrochemical Society. [DOI: 10.1149/2.0431409jes] All rights reserved. Manuscript submitted March 19, 2014; revised manuscript received May 6, 2014. Published June 3, 2014. Chloride (Cl−) is a major fuel cell contaminant1 that can be in-troduced into the cell through airborne salts. Moreover, the Pt-based catalysts may also contain a trace of Cl − that is not completely re-moved after synthesis using chloride-containing precursors.2 The Cl− impurity is detrimental to the performance of proton exchange mem-brane fuel cells (PEMFCs).3–5 The presence of Cl − enhances plat-inum (Pt) dissolution,6–8 which accelerates the degradation of th