Graphene Aerogel for Super Lightweight High-Performance Polymer Electrolyte Fuel Cells

Polymer electrolyte fuel cells (PEFCs), which produce electricity with near-zero pollution, have attracted significant attention as a sustainable power supply system. The development of fuel cell and hydrogen economy align with the scopes of Industrial Strategy: building a Britain fit for the future, Department for Business, Energy & Industrial Strategy, November 2017 and Road to Zero, Department for Transport, Office for Low Emission Vehicles, July 2018. This will help improve the air we breathe, support the shift to clean growth, and help the UK to seize new economic opportunities. Currently, fuel cells are used successfully in automobile, distributed/stationary and portable power generation applications. However, to improve its specific power and extend hydrogen FCs' wider applications e.g. unmanned flying vehicles (UAVs) and drones, super light-weight FCs technology will be required.

Recent research has revealed the feasibility of using graphene aerogel (GA) as electrodes for electrochemical devices. Its high conductivity, high porosity and high surface area enable its applications of being gas diffusion layer (GDL), flow field plate (FFP), current collector and catalyst support; Super lightweight, flexibility and high compressibility could increase fuel cells mass and volume power densities and lead to alternative shapes. The primary aim of this research is to explore a range of GAs, and use the suitable ones to replace two components in conventional PEFC - GDL and FFP.

Traditional FFP is usually made from carbon/polymer composites, graphite plates or stainless steel; GDL is usually made from high porous carbon paper. They are the two components which contribute the majority of the weight to FCs. In conventional FFP, the ribs partially cover the GDL and the resultant gas-transport distance becomes longer than the inter-channel distance. Water tends to saturate at the thinner portion, consequently, oxygen transport is compromised, leading to nonuniform power generation in the FCs. Using GA to replace these parts may deliver extremely lightweight fuel cells, therefore increased power densities can be achieved. GA has porous fine structure, reactant gases will follow diffusion-based mass transfer mechanism, that will lead to an uniform distribution of the reactants. The hydrophobic property and the pore arrangement of GA will enable the water produced in the cathode to leave the electrode, therefore better water management in fuel cells could be achieved.

To accommodate graphene aerogel fuel cell (GAFC), a polymer based, simplified FC system will be designed and 3D printed at Northumbria University. The majority of the FC testing work will be carried out using this system. Selected samples will also be tested in the National Physical Laboratory using their state-of-the-art fuel cell test station, which contains a unique reference electrode array that can characterise carbon corrosion in the cathode. Owing to the high elasticity and flexible shape, to further improve the water management, two more types of chamber design will be introduced: tubular shape FC body and parallelogram electrode host. Tubular shape will introduce compression and expansion stress on anode and cathode respectively, therefore the cathode will have expanded pore structure which will further facilitate the air / oxygen mass transport and water to leave the electrodes; parallelogram shape will introduce shear strain on the electrodes, to facilitate water management.

Numerical simulation for gas mass transfer, diffusion, heat and water distribution within GAFCs for different structure, shape of GAs and different cell design will be carried out to develop a better understanding of the experimental results.

Further studies of GAFC could include temperature management and gas / air cleaning functions.

Fuel cells are the most energy efficient means of converting chemical energy to electricity and thus have great promise for the replacement of internal combustion engine technologies and batteries. Development of fuel cell technology will reduce global CO2 emissions, improve air quality, contribute to UK energy security and have an enabling role in the move towards a low carbon economy. This aligns with the scope of the and Road to Zero strategy and will support the UK in achieving its CO2 reduction targets, and decrease atmospheric contaminants in urban environments. The technological approaches proposed offer a potential step-change in fuel cell uptake, with huge associated impact. Specifically, this research project will have impact on:

Society and the environment: There are a range of societal impacts, which may result from this research, which would accelerate deployment of graphene aerogel fuel cell for lightweight power system due to improved power densities. New development of fuel cells for automobile industry will bring large amount of investment, creating over thousands of jobs across the UK (Zero Emission Vehicle Summit). Our work will also have impact on the graphene and fuel cell research communities in academia and industry, and more widely upon those interested in understanding and developing novel multifunctional materials, which will be suitable for electrochemical device uses (e.g. batteries and super capacitors).

Knowledge, science and industry: The academic research community will benefit from the fundamental study results, e.g. physical properties of GA, internal structure control, mass transport and water management. We will continue to pioneer, extend and validate the new combined flow field plate (FFP) + gas diffusion layer (GDL) membrane electrodes assembly (MEA) fabrication processes. The fuel cell industry will benefit from the fundamental understanding that this work generates and the new functions, e.g. ultra-light weight and novel shape that the GA will provide to support the development of the new type of polymer electrolyte fuel cells (PEFCs), and that we will specifically work to translate into industry.

Economy and the commercial sector: Over 100 UK companies are highly active in fuel cells and hydrogen energy, and the UK's market could be worth up to $1 billion in 2020 rising to $19 billion in 2050. This research will underpin the development of PEFCs which will be the next generation of such products. In addition, by developing the IP necessary to underpin GA and GAFCs, the UK will have a major advantage if this promising idea is successful and adopted. Our Industrial partners NewCell Technologies will directly benefit from this research for their water electrolysers and cost reduction of their FC manufacturing. Applied Graphene Materials will benefit from the GA and graphene preparation approaches, and new application of their existing graphene products.

People and Government: Positive impact for the people involved in the project will be derived from the expertise developed by the research team, training and transferable skills acquired. The people who we will work with in industry will benefit from interaction with academics and the university environment through the development of alternative approaches and highly creative ideas. General career progression will be accelerated for all those involved in the project as a result of the learning, outputs and advances made. The research in this project will also develop education opportunities for school-age children supported by the NU STEM program which in partnership with The International Centre for Life, North Tyneside Learning Trust, The Institute of Physics and local education authorities. For general FC research, the Government and policy makers will benefit from expert input into the GAFC debate and the technology delivered will provide a new option and dimension for shaping our energy future.