Materials researchers from the University of Wisconsin-Madison (UW-Madison) screened thousands of perovskite compounds using quantum mechanics-based computations.
A solid oxide fuel cell is a type of engine that uses electrochemical processes to "burn" fuels much more efficiently than a traditional combustion engine. They offer much promise as an alternative source of energy for vehicles and buildings.
The main hindrance to their widespread adoption is cost. Solid oxide fuel cells need to be replaced more often than combustion engines because their high operating temperatures caused them to break down much more quickly.
Longer-lasting fuel cells would be cheaper, more attractive
In order to lower their costs, fuel cells needed to last longer and require fewer replacements. Therefore, the UW-Madison team sought out new cathode materials that could permit solid oxide fuel cells to operate at lower and less destructive temperatures. (Related: New stable fuel cell could be the breakthrough that makes energy storage economically feasible.)
"Better cathode catalysts can allow lower-temperature operation, which can increase stability and reduce costs, potentially allowing you to take your building off the electrical grid and instead power it with a solid oxide fuel cell running on natural gas," explained Dane Morgan, a materials science and engineering professor involved with the study.
"If we can get to that point with solid oxide fuel cells, the infrastructure of power to many buildings in the country could change, and it would be a very big transformation to a more decentralized power infrastructure," she concluded.
To this end, they used computational techniques based on quantum mechanics to winnow through more than 2,000 candidate materials from perovskites, a large class of light-absorbent compounds used in newer models of solar panels.
Morgan and her fellow researchers narrowed the list of potential cathode materials down to 52 candidates. In the process, they were able to codify the principles of material design for solid oxide fuel cells and offer recommendations to improve the longevity of currently-used materials.
Screening for stable compounds with high catalytic activity
Standard operating temperatures for solid oxide fuel cells range around 1472 degrees Farenheit, eight times the boiling point of water. This is necessary for the oxygen reduction reaction process by which they provide power.
To enable oxygen reduction reaction at less destructive heat levels, the UW-Madison researchers looked for stable compounds that possessed high catalytic activity. Perovskites seemed to fit the bill, being transitional metals with excellent catalytic activity.
"If you can find new compounds that are both stable under the operating conditions of the fuel cell and highly catalytically active, you can take that stable, highly active material and use it at a reduced temperature while still achieving the desired performance from the fuel cell," said Ryan Jacobs, lead author of the UW-Madison study.
However, oxygen reduction reaction is an extremely complex process. This makes quantitative calculations of a compound's catalytic activity very difficult for computational modeling techniques.
Jacobs' research team bypassed this obstacle by selecting a physical parameter that they could determine with ease. They then provided empirical proof that their proxy parameter correlated with catalytic activity.
Using the data from their oblique approach, the UW-Madison team screened thousands of perovskite compounds and found 52 with suitable levels of catalytic activity. They published the results of their study in the journal Advanced Energy Materials.
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