Platinum recovery through electrochemical process
Abstract
Platinum is one of the most efficient catalyst for proton exchange membrane fuel cells (PEMFC), and significant amounts of this expensive material are required to reach the aimed production of PEMFC functioning vehicles. Polluting recovery Pt recovery process such as pyrometallurgy and hydrometallurgy processes are used so far to reuse the precious metal. However, the presence of fluorine in the polymer present in PEMFC make the recovery process more dangerous because of HF emission. Safer and more sustainable recycle paths must be developed to ensure Pt recovery for future hydrogen mobility development. Here, we propose an efficient non-toxic recovery process for Pt. The one-step process proposed in a patent [1] was developed and optimized to enable the simultaneous Pt electroleaching and electrodeposition in ionic liquid mixture implying 1-Butyl-3-methylimidazolium chloride (BMIM Cl) and 1-Butyl-3-methylimidazolium trifluoromethanesulfonate (BMIM TFSI). The electroleaching of Pt directly from the catalyst coated membrane (CCM) was enabled through the use of metal mixed oxide mesh anodes to ensure the full contact of the Pt nanoparticles with both the anode and the electrolyte. The almost complete electroleaching was obtained by adapting several parameters such as chloride concentration, platinum ions concentration, temperature, and process duration. The process is also compatible for the other type of membrane electrode assembly: gas diffusion layer electrodes (GDE). Platinum electrodeposition occurs on recycled gas diffusion layer (GDL), which avoids the use of new material. A one-step recovery of Pt was developed, directly from CCM to recycle GDL in sustainable and safe ionic liquid mixture as electrolyte. It constitutes a promising and an innovative way to recycle Pt, an expensive and essential metal for the wide development of hydrogen mobility.