Methane fuel cells usually require temperatures of 750 to 1,000 degrees Celsius to run, but a new fuel cell with a new catalyst can run at 500 degrees, cooler than an automobile engine:
That lower temperature could trigger cascading cost savings in the ancillary technology needed to operate a fuel cell, potentially pushing the new cell to commercial viability. The researchers feel confident that engineers can design electric power units around this fuel cell with reasonable effort, something that has eluded previous methane fuel cells.
“Our cell could make for a straightforward, robust overall system that uses cheap stainless steel to make interconnectors,” said Meilin Liu, who led the study and is a Regents’ Professor in Georgia Tech’s School of Material Science and Engineering. Interconnectors are parts that help bring together many fuel cells into a stack, or functional unit.
“Above 750 degrees Celsius, no metal would withstand the temperature without oxidation, so you’d have a lot of trouble getting materials, and they would be extremely expensive and fragile, and contaminate the cell,” Liu said.
“Lowering the temperature to 500 degrees Celsius is a sensation in our world. Very few people have even tried it,” said Ben deGlee, a graduate research assistant in Liu’s lab and one of the first authors of the study. “When you get that low, it makes the job of the engineer designing the stack and connected technologies much easier.”
The new cell also eliminates the need for a major ancillary device called a steam reformer, which is normally needed to convert methane and water into hydrogen fuel.
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Hydrogen is the best fuel for powering fuel cells, but its cost is exorbitant. The researchers figured out how to convert methane to hydrogen in the fuel cell itself via the new catalyst, which is made with cerium, nickel and ruthenium and has the chemical formula Ce0.9Ni0.05Ru0.05O2, abbreviated CNR.
When methane and water molecules come into contact with the catalyst and heat, nickel chemically cleaves the methane molecule. Ruthenium does the same with water. The resulting parts come back together as that very desirable hydrogen (H2) and carbon monoxide (CO), which the researchers surprisingly put to good use.
“CO causes performance problems in most fuel cells, but here, we’re using it as a fuel,” Chen said.
Standard fuel cells run on hydrogen which is very hard to store and transport, because hydrogen causes embrittlement in steels. A lower temperature catalyst for methane is a big breakthrough. However, storage of methane is a problem because it requires high pressures to get adequate amounts on board a vehicle. A better solution would be a (relatively) low temperature catalyst for propane, because propane readily liquifies at moderate pressures, solving the storage issues with methane and hydrogen.
Of course, the percentage of energy derived from carbon is higher in propane than methane, but it is much less than that in gasoline. There is also much less propane than methane in gas and oil wells.