Stability of carbon nanofibre-supported platinum catalysts in the presence of chloride under controlled mass-transfer conditions

Abstract

The effect of chloride on the stability of platinum electrocatalysts was studied by rotating disk measurements in sulfuric acid electrolyte with a continuously increasing concentration of chloride anions. The activity towards oxygen reduction was found to be reduced by a factor of seven when 140 ppm chloride was present. Platinum corrosion was severe at high potentials, presumably accelerated by potential cycling, and greatly enhanced by mass transport. A five-fold increase in corrosion rate was found when the electrode was rotated at 1600 rpm with respect to stagnant conditions. At potentials where oxygen reduction occurs, dissolved Pt can be redeposited on the electrode. The Pt dissolution rate increased with increasing Cl -concentration up to 20 ppm. Above this threshold the corrosion rate was unaffected by increases in Cl -content.

The influence of chloride impurities on Pt/C fuel cell catalyst corrosion

“…[8][9][10][11] On the other hand, chloride promotes platinum corrosion, 12 especially under potential cycling conditions. 7,13 The platinum that is dissolved during corrosion can then redeposit inside the PEMFC membrane 14 or on the top of the catalyst film, as demonstrated in ex situ RDE experiments. 15 In this work we show, for the first time, that chloride not only enhances the corrosion rate but essentially changes the corrosion mechanism when compared to a non-chloride environment.…”

“…S3a and b (ESI †) reveals that the potentiostatic stress test is much less damaging (less Pt gets removed) than the potentiodynamic test -with or without the presence of Cl À -which is consistent with the literature. 2,5,13 In conclusion, a combination of cyclic voltammetry, flow system and on-line ICP-MS platinum concentration measurements (EFC-ICP-MS) was used to study the potentiodynamic corrosion of commercial Pt/C electrocatalysts in perchloric acid in the presence of Cl À . It was shown that chloride affects the platinum corrosion in three ways.…”

Environmentally Friendly Carbon‐Preserving Recovery of Noble Metals From Supported Fuel Cell Catalysts

“…[16] To palov et al also showedt hat the dissolution of Pt in an acidic electrolyte occurs mainly during the cathodic scan. [14a] Parameters that have been suggested to accelerate Pt dissolution are low pH values, [14a, 17] high potentials, [7a, 14a, 18] hight emperatures, [19] the presence of Cl À ions, [10,19,20] O 2 - [21] or CO-saturated electrolytes, [22] and potential-dynamic conditions. [23] It is important to mention that most dissolution studies of platinum have been performed on bulk metal.…”