Bipolar plates (BPPs) are essential components in proton exchange membrane (PEM) fuel cells, playing a crucial role in the electrochemical reactions that generate power. These plates not only provide structural support but also facilitate the flow of reactant gases and manage water within the fuel cell system. As the market for PEM fuel cells is projected to exceed $500 million by 2036, the choice of materials for these plates has become increasingly significant.

A recent analysis by Dr. Conor O’Brien, a principal technology analyst at IDTechEx, delves into the ongoing competition between graphite and metal as materials for bipolar plates. Each material offers distinct advantages and challenges that impact fuel cell performance and manufacturing processes.

Graphite plates are known for their excellent corrosion resistance and thermal conductivity, making them suitable for applications where lightweight design is critical. However, their brittleness can complicate manufacturing, particularly for complex flow field designs. To mitigate this issue, manufacturers often use binder materials like phenolic resins to enhance the structural integrity of graphite plates.

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On the other hand, metal plates, which can be made from materials such as aluminum, steel, and titanium, provide superior mechanical strength. This allows for thinner plates, which can lead to higher power density in fuel cells. Furthermore, metal plates exhibit lower hydrogen permeation rates, a crucial factor for preventing gas mixtures within the cells. While graphite plates have a hydrogen permeation rate of less than 10 mol/(cm s bar), metal plates can achieve rates around 1×10-9 mol/(cm s bar).

Electrical conductivity is another important consideration. Metals typically used for bipolar plates boast high electrical conductivities, often exceeding 1 M S/m, compared to the 1-5 K S/m range for graphite. However, in terms of thermal conductivity, graphite generally outperforms metal plates, as the anti-corrosion coatings applied to metal can hinder thermal efficiency.

Cost is a significant factor in the material selection process. IDTechEx’s analysis indicates that metal plates are expected to cost approximately double that of graphite plates over the next decade. This economic consideration is likely to drive the adoption of graphite plates in applications where power density is not the primary concern, such as in heavy-duty vehicles, marine applications, and stationary fuel cells. Conversely, metal plates are anticipated to see increased use in passenger vehicles where high power density is essential.

As the demand for PEM fuel cells continues to grow across various sectors, understanding the strengths and weaknesses of bipolar plate materials will be critical for manufacturers and stakeholders in the fuel cell industry. IDTechEx’s report, “Materials for PEM Fuel Cells 2026–2036: Technologies, Markets, Players,” provides a comprehensive overview of market trends, competitive technology benchmarking, and forecasts segmented by application, offering valuable insights into this evolving market landscape.