6 Crucial Metals for the Future of Fuel Cells
Flip on any news channel and one topic may dominate the deadlines: fuel cells and renewable energy. We constantly hear of the potential of fuel cells to replace fossil fuels. Reports tell us they’ll be over 400 million fuel cell-powered cars on the roads by 2050. We hear about future fuel cell-powered airplanes, boats and trains. The global fuel cell market, experts say, will reach US$ 42.3 Billion by 2030 (up from US$ 5.63 billion today).
But for all of these to happen, the world needs something which is in short supply: catalyst metals. Fuel cells rely on these metals as catalysts to speed up the chemical reactions that take place inside of them, meaning they can operate at reasonable temperatures. But if they’re in short supply, what exciting new metals are researchers investigating to replace them? Below you’ll find 6 examples of unusual metals that may prove vital to the functioning of fuel cells in the future.
The most common metal used as catalysts in fuel cells is platinum. Why platinum? This metal absorbs reactants strongly enough to create a reaction yet not so strong that it becomes blocked. It’s selective, meaning it rarely produces undesirable by-products. It’s also incredibly stable, being able to withstand the operating environment of the fuel cell without undergoing any undesirable reactions. The one drawback? It’s extremely expensive. This cost is passed on to fuel cell consumers, with around 60% of the price of a fuel cell stack being the cost of the platinum for the catalyst. This means fuel cell prices currently remain high and out of reach to many.
“The researchers found that cobalt nitride had a near identical efficiency to platinum but cost 475 times less.”
2. Cobalt Nitrides
Researchers at Cornell University have recently been investigating how to reduce the cost of fuel cells by creating a cheaper catalyst. They’ve discovered that transition metal nitrides (TMNs) can have the same qualities as platinum but cost a fraction of the price. These compounds are derived from cobalt, manganese, iron and other transition metals. They’re able to conduct electricity, but most importantly, when they’re exposed to air they form a thin oxygen-based outer shell that makes a perfect surface for catalyzing chemical reactions.
The researchers found that cobalt nitride had a near identical efficiency to platinum but cost 475 times less. This would make fuel cells far cheaper, increasing their adoption and speeding up the transition to renewable energy.
Nickel – another inexpensive metal – has been found to potentially play a key role in the future of fuel cells. Researchers at the University of Wisconsin-Madison have been attempting to create a catalyst formed of a solid nickel core surrounded by a carbon shell. They’ve found that, when combined with a cobalt-manganese cathode, their fuel cell is able to produce a respectable amount of power (200 milliwatts per square centimeter) while costing a fraction of the price.
“The bottleneck for this technology to become widely adopted is the cost of the materials needed, including the electrocatalysts employed, which in most cases are expensive platinum-group elements,” says Manos Mavrikakis, a professor of chemical and biological engineering at the University of Wisconsin-Madison. “In this work we demonstrated that cheap, non-precious metals, such as nickel, can be used effectively, both for the cathode and anode electrodes of the fuel cell.”
“We have developed a new approach to make a range of ‘single atom’ catalysts that offer an opportunity to allow a range of new chemical and electrochemical processes”
- Dr. Asad Mehmood
Scientists are also hard at work pioneering a method for creating low-cost fuel cell catalysts using a rare earth element: lanthanum. This soft, silvery-white metal can be made into an alloy that works perfectly as a fuel cell catalyst. The research team, led by Siyuan Zhu of Chinese Academy of Sciences, developed a new technique for binding high-cost platinum with low-cost lanthanum to create an alloy that not only works as a catalyst for advanced fuel cells, but is also relatively inexpensive.
The team did this by infusing lanthanum salts and trimesic acid with platinum at around 900 °C, before stress testing the alloy. To their surprise, they found that the alloy had superior stability over 30,000 cycles.
After proving the effectiveness of lanthanum as an alloy partner with platinum, the researchers are now interested in testing other rare earth elements to see if they can improve upon lanthanum's catalytic performance.
Another metal researchers are investigating that could replace platinum in fuel cell stacks is iron. The big breakthrough came from a team led by Professor Anthony Kucernak of Imperial College London. While standard iron is not a particularly reactive metal, Professor Kucernak and his team were able to create ‘single-atom iron’ – where iron is dispersed as single atoms. As opposed to ‘bulk iron’ (where the atoms are clustered together), single-atom iron is much more reactive, making it a perfect solution for catalysts in fuel cells.
“We have developed a new approach to make a range of ‘single atom’ catalysts that offer an opportunity to allow a range of new chemical and electrochemical processes”, said first author Dr. Asad Mehmood, from Imperial College’s Department of Chemistry.
"Specifically, we used a unique synthetic method, called transmetallation, to avoid forming iron clusters during synthesis. This process should be beneficial to other scientists looking to prepare a similar type of catalyst.”
The team are currently working to improve the stability of the catalyst so that it matches platinum in not only performance but durability as well.
Palladium has been used as a catalyst in fuel cells for decades. Belonging to the same group in the periodic table as platinum, palladium is known for its stability, selectivity and durability. So, why isn’t this metal widely used? In recent years the price of palladium has surpassed even that of platinum, and with limited global supply, this metal is not seen as a viable catalyst for future fuel cell development.