Fuel Cells

Our advanced nonwoven materials play an important role in enabling emerging technologies; fuel cells are a prime example of this. TFP has been developing gas diffusion layer (GDL) materials for over 30 years, building the capability, expertise and capacity to meet the forecast growth in fuel cell production.

TFP has been developing and optimising material for fuel cell GDLs since 1988, working alongside some of the leading companies in the industry.  This long term commitment to fuel cell development and growth has facilitated a comprehensive understanding of the necessary material characteristics to achieve a high performance GDL substrate.   

The result is a range of carbon veils and mats which can be tailored to suit the requirements of both stationary and portable fuel cell systems. To date our nonwovens have been used successfully as GDLs in proton electrolyte membrane (PEMFC), phosphoric acid (PAFC) & direct methanol (DMFC) fuel cells.

 

WHAT IS A FUEL CELL? 

A fuel cell is an electrochemical device that combines hydrogen (or hydrogen-rich) fuel and oxygen to produce electricity, heat and water. It is much cleaner and more efficient than an internal combustion engine (ICE) as it does so without burning the fuel. Essentially more of the fuel is converted into electricity and less into heat. 

The active components of a fuel cell are combined in the membrane electrode assembly (MEA), which is composed of an anode, a cathode and an electrolyte membrane. Hydrogen fuel is supplied to the anode, and oxygen to the cathode, via the bipolar plates. The anode is coated with a catalyst which accelerates the conversion of hydrogen to protons and electrons. The electrolyte membrane is selective to protons only, allowing them to pass through to the cathode. The electrons must move via an external circuit generating an electrical current and excess heat. At the cathode the protons, electrons and oxygen combine to generate a water molecule, the only by-product of the process.

Fuel Cell schematic

Individual fuel cells can be compiled to form stacks, which in turn can be combined into larger systems. This means that fuel cell systems vary significantly in both size and power, ranging from portable systems for transportation to large scale installations that provide electricity for high energy demand applications such as schools and hospitals.

 

THE GDL AND ITS FUNCTION

TFP's carbon nonwoven is widely utilised as a substrate for the GDL, a critical component of the MEA which is the heart of the fuel cell. The GDL forms the basis of both the anode and cathode, and is responsible for water management, the transport of reactants, electricity and heat, as well as providing structural support to the assembly.

The GDL must be both electrically and thermally conductive to allow current flow, and have a suitable pore structure to optimise mass transport. The structure must also exhibit the correct balance of hydrophobicity, to manage the movement of water and gases in the MEA. This latter property is critical to the efficient operation of the cell; if the GDL is too wet during operation the by-product (water) is not being effectively removed, flooding may occur and reactant gas movement is impeded. Equally, if the GDL is too dry then the membrane will dry out causing higher resistance. In both cases the performance of the cell is reduced.

The properties of our carbon nonwovens fulfil the performance requirements and material characteristics needed from a GDL substrate and are widely used as such. These attributes include:

CONTROLLED POROSITY - Our veils are highly porous and the pore structure can be tailored to accommodate different types of carbonaceous filler and post treatments. 

CONDUCTIVITY - TFP's carbon nonwovens have high in-plane & through-plane electrical and thermal conductivity, so effective electrical conduction and heat transfer between the catalyst and the current collector plates can occur. 

CHEMICAL RESISTANCE - TFP's range of carbon mats and veils inherently exhibit good chemical & corrosion resistance to reactant gases.   

HIGH SURFACE AREA - Our materials are highly porous and provide a large surface area. This aids optimum control of reactant gas and water movement during operation, helping to maintain effective mass transport and efficient cell performance. 

DURABILITY - Our nonwovens provide excellent durability & strength. They exhibit controllable and repeatable compressibility. This is important both in stack assembly to accommodate thickness variation in cell stack components, as well as during operation to adapt to the thermal expansion seen in larger fuel cell stacks. 

EVEN SURFACE - The superior even fibre distribution characteristic of our nonwovens provides a suitable architecture for application of a smooth microporous layer coating.

 

Contact us for more information about our carbon nonwovens and their use as GDL substrates.