Prototype Demonstration of Innovative and Sustainable Recycling of Materials in Polymer Electrolyte Membrane Fuel Cells and Electrolyzers
Authors: Yildirim Hakan , Larsen Mikkel , Andersen Shuang Ma , Sharma Raghunandan , Karade Swapnil S. , Larsen Lars Christian , Beyer Nikolaj 
Published: December 2024

Low-temperature (LT) polymer electrolyte membrane (PEM) fuel cells (FCs) and electrolysis cells (ECs) contain valuable materials such as platinum-group metals (PGMs) and perfluorosulphonic acid (PFSA) polymer. The Danish companies IRD Fuel Cells A/S and CriMaRec ApS together with the University of Southern Denmark are developing and scaling up efficient and environmentally friendly processes to recycle PGMs, mainly platinum (Pt) and iridium (Ir), with the aim of establishing production alternatives to the costly, energy-intensive, and pollutive conventional processes. The approach is based on patented electrochemical methods involving potential cycling [1,2]. The efforts also comprise recycling or reuse of PFSA polymer as an alternative to incineration. The established outcomes are excellently performing LT-PEMFC&EC membrane–electrode assemblies (MEAs) containing PFSA material recovered from spent MEAs and PGMs recycled from MEAs [3,4] as well as from existing scrap resources such as spent catalysts from exhaust systems of automobiles [5].

In this presentation we shall provide the main results proving our PGM-recycling concepts for Pt and Ir catalysts. Pt and Ir compounds (such as (NH4)2[PtCl6], Pt(NO3)2, and IrCl3) obtained from the processing of spent MEAs and spent autocatalysts were found to have the same qualities as those of commercial equivalents, and new electrocatalyst products (Pt/C and IrO
x
nanoparticles) made from these recycling compounds show properties and performances that are similar to or better than those produced from fresh precursors. Our development of the PGM-recovery processes into pilot-scale production is also presented. Two reactors with volumes of 18 dm3 and 50 dm3, respectively, have been designed, constructed, and optimized for extraction of PGMs from autocatalyst material and MEAs, respectively. In preliminary runs validating the recovery processes in these prototype reactors, 7.3 g of PGM (mainly Pt and palladium (Pd)) were recovered from a 4.5-kg batch of autocatalyst material with an estimated efficiency of 91 %, while 15.4 g of PGM (Pt and ruthenium (Ru)) were recovered from a 0.7-kg batch of LT-PEMFC MEAs with an efficiency of around 93 %. The reactor processes involve low energy consumption, low emissions, and a cycle time less than 2 h – in very great contrast to the conventional recovery processes – and the associated costs are in the order of 10 % of the PGM market price. Furthermore, we present our optimization of the recovery and regeneration of PFSA from the membranes of spent MEAs and the successful reapplication of this material as ionomer in new LT-PEMFC&EC MEAs. The feasibility of the PFSA recycling has been demonstrated as the performances of these new MEAs are similar to or better than those of MEAs prepared using fresh commercial ionomer. On top of these results, we present strong performances of LT-PEMFC&EC MEAs with recycled Pt/C cathode and IrO
x
anode electrocatalysts, respectively.

The perspectives of this work are that a highly competitive large-scale production of LT-PEMFC&EC MEAs containing recycled PGM and PFSA will allow the MEA manufacturer to offer its customers the cost-reducing possibility of returning the spent MEAs for recycling. It can also ensure adequate reuse and/or recycling of production process waste, thus reducing the amount of scrap material. Moreover, it will facilitate the flow of secondary (recycled) PGMs from declining industrial sectors into the hydrogen-energy sector, securing for the latter the supply of these critical raw materials and decreasing the dependence on primary (mined) PGM. The green transition from fossil-fuel-based energy to renewable energy is thus accelerated, with the cost of the PEMFC&EC technology being considerably reduced and its deployment accordingly promoted.

Acknowledgement

The work is supported by the Energy Technology Development and Demonstration Programme (EUDP) of the Danish Energy Agency through the project 64019-0551 3R – Recycle, Reuse, Reduce.