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Scientists Boost Catalytic Activity for Key Chemical Reaction in Fuel Cells
(Please note, release from Brookhaven National Laboratory—copyright concerns are nil.)
https://www.bnl.gov/newsroom/news.php?a=11901
[font face=Serif][font size=5]Scientists Boost Catalytic Activity for Key Chemical Reaction in Fuel Cells[/font]
[font size=4]New platinum-based catalysts with tensile surface strain could improve fuel cell efficiency[/font]
December 16, 2016
[font size=3]UPTON, NY—Fuel cells are a promising technology for clean and efficient electrical power generation, but their cost, activity, and durability are key challenges to commercialization. Today's fuel cells use expensive platinum (Pt)-based nanoparticles as catalysts to accelerate the reactions involved in converting the chemical energy from renewable fuels—such as hydrogen, methanol, and ethanol—into electrical energy. Catalysts that incorporate less expensive metals inside the nanoparticles can help reduce cost and improve activity and durability, but further improvements to these catalysts are required before these fuel cells can be used in vehicles, generators, and other applications.
Now, scientists from the U.S. Department of Energy's (DOE) Brookhaven National Laboratory, California State University–Northridge, Soochow University, Peking University, and Shanghai Institute of Applied Physics have developed catalysts that can undergo 50,000 voltage cycles with a negligible decay in their catalytic activity and no apparent changes in their structure or elemental composition. As described in a paper published in the December 16 issue of Science, the catalysts are "nanoplates" that contain an atomically ordered Pt and lead (Pb) core surrounded by a thick uniform shell of four Pt layers.
To date, the most successful catalysts for boosting the activity of the oxygen reduction reaction (ORR)—a very slow reaction that significantly limits fuel cell efficiency—have been of the Pt-based core-shell structure. However, these catalysts typically have a thin and incomplete shell (owing to their difficult synthesis), which over time allows the acid from the fuel cell environment to leach into the core and react with the other metals inside, resulting in poor long-term stability and a short catalyst lifetime.
"The goal is to make the ORR as fast as possible with catalysts that have the least amount of platinum and the most stable operation over time," said corresponding author Dong Su, a scientist at Brookhaven Lab's Center for Functional Nanomaterials (CFN), a DOE Office of Science User Facility, who led the electron microscopy work to characterize the nanoplates. "Our PtPb/Pt catalysts show high ORR activity and stability—two parameters that are key to enabling a hydrogen economy—placing them among the most efficient and stable bimetallic catalysts reported for ORR."
…
In durability tests simulating fuel cell voltage cycling, Su's collaborators found that after 50,000 cycles there was almost no change in the amount of generated electrical current. In other words, the nanoplates had minimal decay in catalytic activity. After this many cycles, most catalysts exhibit some activity loss, with some losing more than half of their original activity.
…[/font][/font]
http://science.sciencemag.org/content/354/6318/1410[font size=4]New platinum-based catalysts with tensile surface strain could improve fuel cell efficiency[/font]
December 16, 2016
[font size=3]UPTON, NY—Fuel cells are a promising technology for clean and efficient electrical power generation, but their cost, activity, and durability are key challenges to commercialization. Today's fuel cells use expensive platinum (Pt)-based nanoparticles as catalysts to accelerate the reactions involved in converting the chemical energy from renewable fuels—such as hydrogen, methanol, and ethanol—into electrical energy. Catalysts that incorporate less expensive metals inside the nanoparticles can help reduce cost and improve activity and durability, but further improvements to these catalysts are required before these fuel cells can be used in vehicles, generators, and other applications.
Now, scientists from the U.S. Department of Energy's (DOE) Brookhaven National Laboratory, California State University–Northridge, Soochow University, Peking University, and Shanghai Institute of Applied Physics have developed catalysts that can undergo 50,000 voltage cycles with a negligible decay in their catalytic activity and no apparent changes in their structure or elemental composition. As described in a paper published in the December 16 issue of Science, the catalysts are "nanoplates" that contain an atomically ordered Pt and lead (Pb) core surrounded by a thick uniform shell of four Pt layers.
To date, the most successful catalysts for boosting the activity of the oxygen reduction reaction (ORR)—a very slow reaction that significantly limits fuel cell efficiency—have been of the Pt-based core-shell structure. However, these catalysts typically have a thin and incomplete shell (owing to their difficult synthesis), which over time allows the acid from the fuel cell environment to leach into the core and react with the other metals inside, resulting in poor long-term stability and a short catalyst lifetime.
"The goal is to make the ORR as fast as possible with catalysts that have the least amount of platinum and the most stable operation over time," said corresponding author Dong Su, a scientist at Brookhaven Lab's Center for Functional Nanomaterials (CFN), a DOE Office of Science User Facility, who led the electron microscopy work to characterize the nanoplates. "Our PtPb/Pt catalysts show high ORR activity and stability—two parameters that are key to enabling a hydrogen economy—placing them among the most efficient and stable bimetallic catalysts reported for ORR."
…
In durability tests simulating fuel cell voltage cycling, Su's collaborators found that after 50,000 cycles there was almost no change in the amount of generated electrical current. In other words, the nanoplates had minimal decay in catalytic activity. After this many cycles, most catalysts exhibit some activity loss, with some losing more than half of their original activity.
…[/font][/font]
