Improving the water-handling of proton exchange membrane fuel cells

Hydrogen proton exchange membrane fuel cells (PEMFCs) are a key technology in enabling the transition to net-zero carbon energy. Hydrogen powered fuel cell stacks have been demonstrated to be eminently suitable for powering cars and especially trucks, because battery solutions are not viable for most larger vehicles. A recent Hydrogen Council report (link below) emphasises the synergy in using both battery electric vehicles (BEVs) and fuel cell electric vehicles (FCEVs) to have a major impact on transport derived CO2 emissions. The heavy duty truck market is expected to be the first to become fully commercialised FCEV application due to the less-demanding infrastructure network requirements.

However, a key issue severely impacting the performance and efficiency of PEMFCs is water flooding. Water flooding occurs in the cathode-side catalyst layer whereby water generated in the cathode reaction condenses out in the pores of the catalyst support thereby blocking access for in-coming oxygen. Hydrophobic ionomer is added to the cathode catalyst layer to attempt to mitigate against flooding. In order to design the optimal formulation and fabrication process for the cathode catalyst layer, it is necessary to understand the relationship between the properties of the layer, especially pore size, pore connectivity and surface wettability/hydrophobicity, and the performance in the actual PEMFC. However, it has been found that current characterisation methods used are unable to distinguish sufficiently between the pore network and wettability characteristics of different layers to predict differences in their eventual PEMFC performance. Hence, new characterisation techniques are needed, and this is the aim of this project. The objectives of this project are to test three such candidate techniques for suitability. NMR spectroscopy and relaxometry of hyperpolarised (hp) krypton and xenon have been shown to be sensitive probes of pore size and the spatial distribution of hydro-phobic/-philic surfaces within a probed network. We, thus, intend to test hp Kr and hp Xe NMR techniques for determining the spatial distribution of ionomer and inception of water adsorption within cathode pore networks. The second candidate is adsorption calorimetry. Previous combined gravimetric and calorimetric studies of gas uptake in gas shales have suggested the technique can readily assess the spatial arrangement and juxtaposition of pore condensate in complex geometries, and its impact on mass transport. This technique will also be tried on catalyst layers. Finally, serial water adsorption and mercury porosimetry studies on catalyst pellets have revealed that this method can characterise the spatial distribution of the adsorbed water and the impact on percolation pathways within the pore network, and will thus be tested on cathode catalyst layers. We will also aim to develop a characterisation technique that can be used as a quality control, near-to-line measurement during manufacturing.

The proposed Centre will benefit the following groups

1. Students - develop their professional skills, a broad technical and societal knowledge of the sector and a wider appreciation of the role decarbonised fuel systems will play in the UK and internationally. They will develop a strong network of peers who they can draw on in their professional careers. We will continue to offer our training to other Research Council PhD students and cross-fertilise our training with that offered under other CDT programmes, and similar initiatives where that develops mutual benefit. We will further enhance this offering by encouraging industrialists to undertake some of our training as Professional Development ensuring a broadening of the training cohort beyond academe. Students will be very employable due to their knowledge, skills and broad industrial understanding.
2. Industrial partners - Companies identify research priorities that underpin their long-term business goals and can access state of the art facilities within the HEIs involved to support that research. They do not need to pre-define the scope of their work at the outset, so that the Centre can remain responsive to their developing research needs. They may develop new products, services or models and have access to a potential employee cohort, with an advanced skill base. We have already established a track record in our predecessor CDTs, with graduates now acting as research managers and project supervisors within industry
3. Academic partners - accelerating research within the Energy research community in each HEI. We will develop the next generation of researchers and research leaders with a broader perspective than traditional PhD research and create a bedrock of research expertise within each HEI, developing supervisory skills across a broad range of topics and faculties and supporting HEIs' goals of high quality publications leading to research impacts and an informed group of educators within each HEI. .
4. Government and regulators - we will liaise with national and regional regulators and policy makers. We will conduct research directly aligned with the Government's Clean Growth Strategy, Mission Innovation and with the Industrial Strategy Challenge Fund's theme Prosper from the Energy Revolution, to help meet emission, energy security and affordability targets and we will seek to inform developing energy policy through new findings and impartial scientific advice. We will help to provide the skills base and future innovators to enable growth in the decarbonised energy sector.
5. Wider society and the publics - developing technologies to reduce carbon emissions and reduce the cost of a transition to a low carbon economy. Need to ascertain the publics' views on the proposed new technologies to ensure we are aligned with their views and that there will be general acceptance of the new technologies. Public engagement will be a two-way conversation where researchers will listen to the views of different publics, acknowledging that there are many publics and not just one uniform group. We will actively engage with public from including schools, our local communities and the 'interested' public, seeking to be honest providers of unbiased technical information in a way that is correct yet accessible.