Electrochemical dissolution of platinum and ruthenium from membrane electrode assemblies of polymer electrolyte fuel cells

Abstract

To establish a recovery method for noble metals from membrane electrode assemblies (MEAs) of spent polymer electrolyte fuel cells (PEFCs) without the use of strong acids, electrochemical dissolution tests for Pt and Ru from MEAs were conducted. By using square potential waves, 93.2% of the Pt and 98.4% of the Ru dissolved from a MEA in 1 mol L-1 HCl at room temperature when oxidation and reduction potentials were at 1.5 and 0.1 V vs. SHE and the holding times for both were 15 s per cycle. The dissolution of Pt and Ru became remarkable when the oxidation potential was 1.4 V vs. SHE and gradually decreased at more positive potentials. These results indicate that competitive reactions exist in the dissolution process. In addition, the effects of H+ and Cl- concentrations on the dissolution ratios were investigated. The dissolution ratios of Pt and Ru were small in solutions with low Cl- and high H+ concentrations ([Cl-] = 0.01 mol L-1, [H+] = 1 mol L-1); however, 50.6% of the Pt and 27.9% of the Ru dissolved in solutions with high Cl- and low H+ concentrations ([Cl-] = 1 mol L-1, [H+] = 0.01 mol L-1). Thus, we verified that the electrochemical dissolution method was adaptable to the recovery of noble metals from MEAs and that strong acids were not needed.