Recovery of metal value from end of life PEMFC

With potential widespread uptake of fuel cell technologies in many areas of energy conversion, there is an increasing need to address new ways to reclaim the significant value associated with end-of-life fuel cell stacks. The term fuel cell can be applied to a wide range of electrochemical devices which use a variety of materials; however, the type with potentially the largest market penetration is the polymer electrolyte membrane fuel cell (PEMFC). Although there has been much research into alternatives, the usual electrocatalyst combinations are based on Pt and Ru, both of which are extremely costly. There are several models such as metal leasing which can help address this, but clearly in all cases to facilitate broad market uptake, efficient and effective means of recovery of these metals by a scalable route needs to be developed. Traditional techniques for recovery of these metals, such as pyrometallurgical routes (smelting) has some particular energy and environmental problems as well as constraints which would make large scale recovery of Pt and Ru by these routes impossible.

The research proposed here intends to provide the fundamental knowledge required for the development of a process which addresses the following important requirements:
1) Low process cost and complexity
2) Low environmental impact - direct and in terms of emissions from energy input
3) Safe process

An electrochemical based closed loop process is proposed which short cuts a lot of the extraction steps to give selective recovery of each metal constituent in turn. The idealised process consists of two coupled reactors, the leach reactor in which the metals are dissolved selectively and a membrane divided electrochemical reactor, in which the metals are deposited sequentially from solution whilst the oxidant is regenerated simultaneously. This process in conjunction chemical systems to be investigated to facilitate it will produce a much safer and more energy efficient process which could significantly reduce the lifecycle costs of fuel cells. However, there are some real challenges that have to be addressed before a practical process could be deployed. The project will explore in detail:

1) The leaching kinetics and mechanisms for these metals and how intimate lamination of the catalyst layers into the membrane affects recovery rates.
2) Whether there is sufficient access to the precious metal through the pore structures of the carbons used when the catalyst has been laminated without the need for a membrane dissolution or partial dissolution process
3) Selective and sequential recovery of each metal component which will require detailed investigation into the deposition kinetics of each metal and design of a suitable cathode for the electrochemical reactor

Fuel cells promise to be a significant part of the future energy conversion market, playing a key role in the decentralisation and diversification of UK electricity generation, finding application in remote and combined heat and power (CHP) systems. The UK has some significant interests in the complete supply chain from raw materials to system integrators with range from small SMEs such as Intelligent Energy and Acal Energy, to large multinationals such as Centrica and Johnson Matthey. If the example is taken of a fuel cell micro-CHP system, to displace the current condensing boiler technology, then the UK market is worth around 1.5 M units per year. To support this shift in technology, complementary supply and reclamation routes clearly need to be established now to help the most efficient and successful uptake of the technology. If successful this research, by reducing life-cycle costs, could quicken the introduction of Fuel Cells in many applications.

Despite the significant world interest in fuel cell technologies there has been little specific research to address the issues of recovering values from them when they reach their end of life. This project attempts to start to redress this situation by investigating the key reactions will would facilitate the safe, efficient and economic recovery of the Ru and Pt content of spent membrane electrode assemblies (MEAs) from polymer electrolyte fuel cells (PEMFCs). The results will be of direct interest to the fuel cell community both academic researchers and industry. The research proposed has the potential to reduce the lifecycle cost of PEMFC systems and facilitate the more rapid uptake of fuel cell technologies.

The research will directly benefit the following groups by potentially quickening uptake of fuel cell technology:
* Fuel cell developers nationally such as Johnson Matthey, Acal Energy, Intelligent Energy and internationally such as Ballard Power Systems and Plug Power.
* Fuel cell supply chain including direct stack materials and component suppliers such as Johnson Matthey as well as balance of plant suppliers like Senior and Modine
* Gas processing companies such as BOC and Air Products.

The chemistry and process principles will be of interest to the following groups:
* Precious metal refiners such as Johnson Matthey and academics investigating precious metal chemistries and processes such as groups at Cardiff and Southampton Universities.
* Those involved in the reclamation of precious metals from Waste Electrical and Electronic Equipment such as Biffa and EasyWEEE and Recupel where the process and chemistry might be possibly directly applied to meet the challenges of this area.

In these cases where companies are UK based or have a strong UK presence there is potential for economic benefit to the UK. There are both direct and indirect benefits to UK health and wellbeing.

* If an environmentally benign low energy process route can be established then reduced noxious emissions compared to conventional routes would have respiratory health benefits.
* If fuel cell uptake is quickened and displaces technologies with harmful emissions close to human populations then again the respiratory health of the nation can benefit.

Any improvement in health constitutes a reduction in NHS spending in that area saving funds for other needs.