Platinum recycling from fuel cell-spent electrocatalysts using oxidative leaching in HCl solution

Abstract

The recovery of platinum (Pt) from electrocatalysts in spent proton exchange membrane fuel cells is promising and important for the sustainable development of such a noble metal. Conventional leaching of Pt in the aqueous phase typically requires the use of high concentration of mineral acids and the presence of strong oxidants owing to its thermodynamic stability and non-reactive properties. In the present study, the dissolution of Pt from a Pt/C fuel cell electrocatalyst was investigated using a simple and efficient process under moderate conditions in chloride media. Notably, the leachability of Pt was high ∼76% in a solution of low concentration HCl 2.0 M at 90 °C for 120 min in the absence of an oxidant. The enhancement of Pt leaching efficiency can be obtained using various oxidizing agents HNO3, H2O2, NaClO and NaClO3, and NaClO3 shown the most effective improvement from 76% to 88%. The dissolution of Pt in a solution of 2.0 M HCl and 3.0 wt% NaClO3 improved to 98% by the increase in leaching temperature from 50 to 90 °C. Kinetic studies indicated that Pt leaching in HCl in the presence of NaClO3 followed a chemical-controlled mechanism with an activation energy (Ea) of 40.6 kJ/mol. Based on the findings of this study, an efficient process is proposed to recover and reuse Pt from an electrocatalyst sample of spent fuel cells, including oxidative leaching, chemical precipitation and laser reduction.