Mixed cation- and anion-exchange hybrid membranes for use in fuel cells, redox flow batteries and electrodialysis cells

The research involves the development of hybrid polymer electrolyte membranes and membrane electrode assemblies (HyMEA) that contain distinct cation(proton)- and anion(alkali)-exchange phases with a defined interface or junction between the phases. Two different approaches will be investigated: Approach 1 (lower risk) will involve the fabrication of HyMEAs using commercially available Nafion ionomers and proton-exchange membranes along with Surrey's previously developed alkaline ionomer formulations and alkaline anion-exchange membranes. The second approach (higher risk involving more fundamental explorations) will involve the synthesis of innovative hybrid membranes from a single precursor polymer film where the distinct cation- and anion-exchange phases are separated by a chemical junction/interface and where there are no interferences from undesirable physical separation phenomena between the phases.The HyMEAs will firstly be evaluated in fuel cells with a preferred embodiment where the acidic phase is located at the anode and the alkaline phase is located at the cathode. The use of HyMEAs will allow the use of low humidity hydrogen and air gas supplies as the water generation in the operating fuel cells is at the cation-/anion-exchange junction, which is located away from the electrodes themselves (water generation in the electrodes in traditional fuel cells can disrupt the supply of the reactant gases, which leads to mass transport derived performance losses); the cation-/anion-exchange junction is ideally located inside the HyMEA for maximum retention of the hydration state of the polymer electrolyte membranes and films for maximum ionic conductivity. The synthetic approaches detailed above were deliberately chosen to allow for HyMEAs and hybrid membranes to be synthesised where the cation-/anion-exchange junctions can be located at controlled (and varying) distances from the anode and cathodes; hence the optimum location of water generation (e.g. near to the anode, near to the cathode, located dead centre) can be determined for each approach. The presence of a high pH cathode will also allow for the use of non-platinum (non-Pt) cathodes (the cathodes of traditional hydrogen fuel cells, where the oxygen reduction reaction kinetics are sluggish, contain the bulk of the Pt content; the anode electrokinetics are superior and hence significantly less Pt can be used at the anodes).Recently, hybrid (bipolar) membranes have been applied to technologies such as redox flow batteries and electrodialysis cells: therefore, the project will also evaluate if the application of the hybrid membranes developed above is pertinent to these technologies. The model systems for this impact assessment will be a vanadium redox flow battery and a sodium formate electrodialysis cell.PRINCIPAL AIMS: To develop a range of HyMEAs that are initially targeted for use in hydrogen fuel cells that require non-humidified gas supplies and that contain non-platinum-group-metal cathodes.ENSUING PROJECT AIMS: An initial feasibility study on the use of the developed hybrid membranes in electrodialysis cells and redox flow batteries to explore the potential impact of the developing technologies in non-energy generation applications (water technologies and energy storage).

The primary commercial beneficiaries of the research (potential wealth generation in 2-10 years) will be companies that are developing / commercialising clean energy and water technologies including materials and components. The programme will generate new knowledge, both fundamental and applied. A direct output of the proposed programme (3-4 year impact window) will be a highly skilled researcher who will have developed multidisciplinary skills and experience of energy generation, energy storage and electrodialysis systems, which are vitally important to the building of sustainable societies; this assists towards the assurance of the trained personnel pipeline. In the long-term, (30-50 years), society itself will be a beneficiary on successful completion of the research as breakthroughs in clean energy generation technologies will have positive impacts on quality of life and health (low pollution levels, mitigation of global warming and energy security). The proposed research programme will involve collaboration with Acta and Mintek. A key advantage of the proposed hybrid fuel cells is the ability to use non-Pt catalysts at the cathode; as such the proposed collaborations with world leaders in the production of non-Pt catalysts, is timely and fully compliments Surrey's alkaline polymer electrolyte expertise. Surrey is now considered to be a world leader in anion-exchange polymer electrolyte materials. Hence, for maximum impact, a 1 - 2 day national workshop on technologies incorporating anion-exchange membranes (including the hybrid membrane systems) will be organised at Surrey in the final 6 months of the proposed project: Academic participants, industrial parties, research councils/policy makers will all be invited. This workshop will help consolidate the UK's leadership in this technological arena and will stimulate new links between the water treatment - clean energy sectors. To further facilitate impact, the results generated from the research will be disseminated at international and UK conferences and meetings (after IP assessment and protection), that are known to attract a mixture of academic participants, policy makers and government agencies, industrial end users and component manufacturers. To foster UK economic competitiveness, the results will also be directly or indirectly fed back into 4 UK consortia, (Alkaline Polymer Electrolyte Fuel Cells (coordinated by a member of the Supergen Fuel Cell Consortium who will act as an indirect link), Supergen Energy Storage and Supergen Biological Fuel Cells), which have associated industrial clubs or industrial collaborators. As is mentioned in the case for support, Surrey started to develop a portfolio of protected IP around alkaline ionomers (identified as a key component for the next breakthrough in alkaline polymer containing fuel cells). The proposed project will explore hybrid membrane fuel cells containing alkaline ionomers and on successful completion will assist in maximising the commercial possibilities applicable to Surrey alkaline ionomer patents. The management of any background and foreground IP will be in consultation with the University's highly successful Research and Enterprise Support Office (see news articles on Surrey Satellite Technology for evidence of excellence). In March 2009, Surrey was awarded a 3.85m Knowledge Transfer Account by the EPSRC, which starts on 01/10/09 and over its 3 year duration Surrey's EPSRC-funded research will drive increased engagement with industrial users and accelerate the exploitation of new technology. Surrey was also awarded funds (Dec 2009) for 2 Doctoral Training Centres (Sustainability for Engineering and Energy Systems & Micro- and NanoMaterials and Technologies). These major awards will maximise the possibilities for generating UK-orientated impact from all of the University's EPSRC funded research and provide clear evidence of Surrey's excellence in the field of novel materials and clean energy.