Ensuring the economic and environmental viability of fuel cell technologies through materials separation and recycling

Recycling as a key of material circularity and societal acceptance

 

Production of energy from renewable sources is one of the keys to face the ongoing environmental crisis. The intermittency of renewable energies (wind, solar) pushed the emergence of energy storage technologies and industries such as the battery industry for storage as electrical energy, or the hydrogen industry for storage as chemical energy. Hydrogen can be produced through water electrolysis during energy overproduction periods to be transported and used on a different location and time using fuel cells, and notably Proton Exchange Membrane Fuel Cells (PEMFCs). These devices can convert hydrogen back into electricity and only emit water and heat, however, they rely on the use of raw materials that are expensive and can be critical or pose environmental issues such as platinum group metals, and perfluorinated polymers. There is a necessity to guarantee the recyclability of the constitutive materials of new PEMFCs systems at the lowest possible environmental and economic cost to ensure the societal acceptance and industrial emergence of PEMFCs.

 

The challenges of recycling in PEMFCs

 

The core of PEMFCs is the membrane electrode assembly (MEA) that is typically constituted by a membrane, with on both sides a metal catalyst system supported onto a conductive material (both constituting an electrode) and a gas diffusion layer. These materials are then hot-pressed to assemble the MEA and are tightly bound together, which can make them hard to separate. In addition, the membrane, which is generally polymeric, can degrade during cell operation.

 

The recycling of metal catalysts from MEAs has attracted much attention due to the high cost of the metals, however, processes that focus only on the metal recovery fail to address the recycling of membranes, that are also valuable materials. Moreover, the main membrane used in PEMFCs is based on perfluorosulfonated polymers that are susceptible to produce highly toxic and persistent per- and poly-fluoroalkyl substances (PFAS), also coined as “eternal chemicals”. Developing recycling processes for MEAs that allow the recovery of all their constitutive material should thus be a strong focus of research and industrial developments.

 

Fixing ambitious targets for recycling processes

 

Within the NICKEFFECT project, PEMFC systems that use Nickel alloys as an alternative catalyst material are developed. The performance of these systems is also evaluated in terms of recyclability as a part of the technical specifications and ambitious targets are set on the recovery of the materials. The project strives to demonstrate the development of a catalytic system concomitantly with a complete recycling process that is able to separate MEA components, then isolate and recycle them in a closed-loop manner, including both catalyst and membrane, to show that such goals are achievable and can become more common in practice.