A green adaptation of the critical resource of platinum group metals (PGMs) from spent autocatalysts to electrocatalysts for renewable power conversion

Abstract

Platinum group metals (PGMs) are state-of-the-art electrocatalyst elements for polymer electrolyte membrane (PEM) fuel cells and electrolysers due to their superb catalytic nature and high robustness. With the rapid renewable energy market expansion and limited PGM natural resources, PGM supply may become a bottleneck for the further growth of PEM technologies. Automobile catalytic convertors (autocatalysts), on the other hand, currently contribute over 50% of the global PGM consumption. Therefore, spent autocatalysts are important secondary sources of PGMs. Here, we demonstrate a green approach for recycling of platinum from spent autocatalysts involving its transformation into electrocatalysts for renewable energy conversion using PEM technology. The approach, unlike conventional PGM recycling by smelting autocatalysts, relies on a mild solution-based process utilising the high surface-to-volume ratio and hence the high activity of nanoparticulate PGMs. The platinum-on-carbon (Pt/C) fuel-cell electrocatalyst synthesised using the recovered Pt precursor exhibits performance similar to that of an equivalent based on a commercial precursor, both in thin-film electrodes and single-cell setups. The demonstrated interconversion of the PGM critical resource from end-of-life autocatalysts to new electrocatalysts opens a bright perspective for further upscaling and a robust material foundation for a sustainable green power transition from fossil-fuel-based waste products to renewable-fuel-based electrochemical systems.