Fuel cells are on the rise as sustainability and decarbonization efforts become more widespread globally due to their ability to help contribute to economies on their way to meeting net zero targets. IDTechEx's report "Materials for PEM Fuel Cells 2024-2034: Technologies, Markets, Players" covers the structures of bipolar plates within fuel cells and the materials used to achieve maximum performance.
The role of bipolar plates within fuel cells
Bipolar plates (BPPs) distribute hydrogen and oxygen evenly throughout the fuel cell to carry out their respective roles as fuel and oxidant. The bipolar plate is also the point at which the generated electric current is collected - though they are only required to be installed in fuel cells with more than one cell.
BPPs take on other responsibilities, including removing water from each cell, humidifying gases, cooling the cells, and separating neighboring cells. They therefore play a large role in the effective running of fuel cells.
The structure of a PEM fuel cell broken down into layers. Source: IDTechEx
Parallel and serpentine form factors for bipolar plates
A variety of form factors are available for bipolar plates, that include parallel flow fields, serpentine flow fields, and interdigitated flow fields.
Parallel flow fields tend to cause gas flow to prefer the route of a single channel, typically the one with the least resistance, meaning that many other channels aren't utilized. As water droplets form in unused channels, gas distribution becomes uneven, and overall cell performance is reduced.
Interdigitated flow fields contain multiple parallel flow fields side by side, with gas flow being pushed down a gas diffusion layer and into the membrane. Excess gas then travels back along this route and into 'exit' channels. IDTechEx reports this BPP form factor is dependent on factors such as the porosity and hydrophobicity of the gas diffusion layer.
Serpentine flow fields utilize one channel rather than multiple, meaning that the uneven gas distribution seen in parallel flow fields isn't as prevalent. However, maintaining constant pressure along the channel is tricky due to the distance between the inlet and the outlet. The possibility of a water drop forming somewhere along the route means that multiple serpentine flow fields are often implemented. This multiple flow field option is descried by IDTechEx as the most popular choice for bipolar plate manufacturers as it proves to be the choice most suited to balancing complexity and cost.
The battle of materials for bipolar plates
Corrosion resistance, electrical conductivity, mechanical strength, thermal conductivity, and gas impermeability are important factors to consider when selecting materials for bipolar plates. IDTechEx outlines the differing strengths of the main material choices - graphite and metal.
Graphite boasts good corrosion resistance without additional coatings, while the cost of manufacturing graphite plates is about 50% lower than metal plates. Graphite also has higher thermal conductivity than metal and is more lightweight with lower material density, meaning that plates can be used for fuel cell stacks.
At the other end of the scale, alongside their far greater costs, the corrosion resistance of metallic bipolar plates is weaker than that of graphite, meaning that coatings are required to maintain functionality within harsh chemical environments. The electrical conductivity of metal, however, is far greater than that of graphite, while the higher mechanical strength of metals enables plates to be made thinner, which can result in higher power density for fuel cells.
Other material types used in the manufacturing of fuel cells and coatings for bipolar plates are covered in detail within IDTechEx's report, "Materials for PEM Fuel Cells 2024-2034: Technologies, Markets, Players", alongside the main applications for fuel cell technologies.
For more information on this report, including downloadable sample pages, please visit www.IDTechEx.com/MPEMFC.
For the full portfolio of energy and decarbonization market research, please see www.IDTechEx.com/Research/Energy.
About IDTechEx
IDTechEx provides trusted independent research on emerging technologies and their markets. Since 1999, we have been helping our clients to understand new technologies, their supply chains, market requirements, opportunities and forecasts. For more information, contact research@IDTechEx.com or visit www.IDTechEx.com.
