Electrochemical recovery of Pt/C electrocatalyst: optimization of the potential range on the leaching process and application to an aged MEA

Abstract

Carbon-supported platinum nanoparticles (Pt/C) are widely used electrocatalysts in proton exchange membrane fuel cell and electrolyzer applications and represent a substantial part of the capital expenditure of these devices. Platinum being a critical raw material, its recovery is critical for the deployment of these technologies. In this contribution, the first step of a recycling protocol, i.e. the leaching of Pt/C, is studied. To avoid the use of concentrated acids and oxidants, the focus of the present study is on the design of an efficient electrochemical protocol. In particular, the values of the upper and lower potential limits have an impact on Pt dissolution efficiency. The upper potential limit should avoid (or at least limit) Pt particles' detachment from the carbon support and the lower potential limit should take into account the competition between the platinum dissolution and the unwanted platinum redeposition. The evolution of the particle morphology and dissolution rate were monitored by coupling a statistical analysis of TEM images and ICP-MS concentration measurements. The cycling potential window was first optimized for a model commercial Pt/C catalyst in a low-chloride concentration electrolyte, leading to a full Pt leaching efficiency (99%). A similar protocol was transferred to more technological objects: MEA aged under realistic conditions. The MEAs were electrochemically treated without any prior GDL separation and the efficiency of the process was demonstrated.

Keywords: MEA recycling; Platinum electrodissolution; Platinum recovery.