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.
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