Closing the loop: life cycle assessment and optimization of a PEMFC platinum-based catalyst recycling process

Abstract

This study is focused on the development of an environmentally friendly recycling method for selective recovery in a closed loop manner of Co and Pt from a Pt₃Co/C catalyst used as the proton exchange membrane fuel cell (PEMFC) cathode. Pt and Co selective separation was carried out using two different hydrometallurgical alternatives based either on ion exchange resin or solvent extraction. The recycling process was optimized in order to maximize the platinum recovery yield, which reached 85% and 78% of the Pt initially present in the membrane-electrode assembly (MEA) using respectively solvent extraction or ion exchange resin separation alternatives. The recovered platinum alkaline solutions have been further used for Pt/C particle synthesis via a modified polyol method and it was shown that although the resin alternative resulted in a slightly lower recovery yield, the catalyst prepared via this alternative had satisfactory morphological and electrochemical properties for the oxygen reduction reaction (ORR) by performing similar to a commercial state-of-art Pt/C catalyst. The feasibility of the closed loop Pt/C catalyst recycling was thus proven. The environmental impacts of the two recycling alternatives have been compared using the life cycle assessment methodology (LCA) and similar impacts have been found for both alternatives from the point of view of the entire MEA life cycle. The ion exchange resin alternative has thus been selected as the most appropriate one.