Fuel cells have become a viable eco-friendly power source, and advancements in the technology continue to be made. As fuel cell technology improves, the importance of using high-purity fuel cell graphite in cells’ bipolar plates is becoming increasingly evident. Here’s a look at the role of graphite within fuel cells and why the quality of graphite used is important.

What Is a Fuel Cell?

Fuel cells operate like miniature power plants that produce electricity. They take in hydrogen and a gas (usually oxygen), and they generate electricity, water and heat through an electrochemical reaction. The electricity is generally the sought-after product, while the water and heat are byproducts.

There are multiple components within a fuel cell, and the structure is complex. With regard to fuel cell graphite, however, the most important components are bipolar plates found on either end of a cell.

Bipolar plates sandwich most of the components within a fuel cell, and they perform multiple functions. These plates distribute fuel and gas into the plate, prevent gases and moisture from leaking out of the plate, remove heat from the active electrochemical portion of the cell, and conduct electrical currents between cells.

In most setups, multiple fuel cells are stacked on one another to produce the amount of power that’s required. Bipolar plates are thus responsible not just for leakage prevention and thermal conductivity within a plate, but also for electrical conductivity between fuel cells’ plates.

Leakage prevention, thermal conductivity and electrical conductivity are the three characteristics of bipolar plates that make high-quality graphite an ideal material to use in these components.

What Kind of Graphite Is Used in Fuel Cells?

The graphite used in bipolar plates must be processed specifically for fuel cells and batteries, as other forms of graphite don’t provide all of the traits that bipolar plates need. Natural flake graphite is usually the raw graphite that’s processed for this purpose.

Natural flake graphite needs to be mechanically or chemically processed or “upgraded” to reach the necessary carbon levels for industrial applications. But the purity level needed for fuel cells is beyond the carbon levels/purity requirements than the other industrial applications, thus the need for a targeted purification process either using high temperature or chemicals. Chemical purification could leave traces of chemicals that could negatively affect the performance of the bipolar plate and fuel cell electrochemical reactions, thus thermal purification found best suited technology. Thermal purification of natural graphite also ensures a consistent level of purity and quality control, which is of paramount importance when dealing with a natural material of varying degree of purity. Thermally purified graphite can be molded directly with some binders to bipolar plates or can be further processed into expanded graphite via a chemical and heat process. Once expanded, the graphite is gradually compressed into mats, which can be further processed into plates that have gas and coolant channels built-in. These are used to form bipolar plates.

After thermal processing, the graphite has the right properties to be used in bipolar plates. The thermally purified natural flake graphite is:

Non-Porous: The thermally purified graphite is transformed into a non-porous structure that won’t leak coolant or moisture. Flake graphite on its own is porous and will let moisture seep out.

Thermally Conductive: The thermally purified graphite has high in-plane thermal conductivity, which effectively transfers heat away from the active area within a fuel cell.

Electrically Conductive: The thermally purified graphite has high in-plane electrical conductivity and high through-plane electrical conductivity. Both forms of electrical conductivity are necessary to pass the electrical current that’s generated between fuel cells and within a circuit.

Non-Corrosive: Thermally purified graphite is non-corrosive when processed to a high standard, which helps extend the lifespan of a fuel cell.

How Does Fuel Cell Graphite Compare to Other Materials Used in Bipolar Plates?

Graphite isn’t the only material that can be used in a fuel cell’s bipolar plates. When compared to each of the other alternatives, however, high-quality fuel cell grade thermally purified graphite has some distinct advantages.

First, stainless steel may be used for bipolar plates. The metal certainly has the mechanical strength that’s required, and it’s formulated to resist corrosion for a long lifespan. Stainless steel lacks sufficient thermal and electrical conductivity for efficient operation, however, and its inefficiency has been one challenge that’s held fuel cell development back. Graphite provides the conductivity that’s required for efficient operation.

Second, some researchers have successfully used gold-plated bipolar plates to create efficient fuel cells. The precious metal is almost ideal, for it’s thermal and electrical conductivity, and doesn’t corrode easily. Gold is a cost-prohibitive solution for the vast majority of fuel cell applications, however, and this has been one reason why fuel cell vehicles have remained above most people’s budgets. Graphite has the same necessary qualities and is a much more affordable material even after it’s processed. Researchers who have recently studied gold for this application even recommended turning to graphite as a more practical material.

Third, low-quality graphite offers the thermal and electrical conductivity that’s required for efficient operation. Low-quality graphite doesn’t last as long as high-quality fuel cell grade thermally purified graphite does, though, as it’s prone to premature corrosion due to the impurities in it. Research has shown that investing in high-quality is more cost-effective when the lifespan of fuel cells is taken into account. Quality primarily refers to purity in this case.

Thus, high-quality fuel cell graphite is the most suitable choice for bipolar plates in the vast majority of applications. It’s the efficient and cost-effective choice.

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Where Are Fuel Cells Used to Deliver Electricity?

Fuel cells have many applications already, and the potential uses will only grow as this technology is developed further. Right now, fuel cells are used to deliver electrical power in commercial, industrial, residential and remote settings. The cells may be used as a primary or backup power source.

Fuel cells are especially useful where other power sources are unavailable. For example, they can deliver reliable electricity to inaccessible and off-grid locations. The cells are easier to install than wind turbines and solar panels, and they aren’t dependent upon the weather to produce electricity.

Additionally, there is great potential for fuel cells in eco-friendly vehicles. As the electric vehicle industry grows, driving range has proven to be a major challenge. Standard electric vehicles are limited by their batteries, only going a maximum distance before they need to recharge. This isn’t practical in many commercial applications where vehicles cover vast distances, and it puts off many individuals who would otherwise consider an electric car. Fuel cells have the ability to deliver eco-friendly electrical power at driving ranges that are comparable to gas or diesel engines’ ranges.

Get High-Quality Thermally Purified Graphite for Fuel Cells

For companies that produce fuel cells, we at Superior Graphite have developed a high-quality graphite for fuel cell and battery applications. FormulaBT™ is designed to be the active ingredient that gets blended with binders to form bipolar plates, and it’s specifically made to have high thermal conductivity, high electrical conductivity and high corrosion resistance. Contact us to learn more about this particular thermally processed chemical-free graphite.

Source:
https://www.thegraphenecouncil.org/blogpost/1501180/356913/Graphite-instead-of-gold-Thin-layers-for-better-hydrogen-cars