May 8, 2018
Professor Anastassia Alexandrova
Professor Anastassia Alexandrova and alum Dr Mai-Anh Ha’s work on endothermic cooling of hypersonic jets featured in Chemical & Engineering News.
 
The research was the result of collaboration between Alexandrova (pictured above), her former graduate student Dr. Mai-Anh Ha (Ph.D.’17) (pictured right), currently a Directors Postdoctoral Fellow in National Renewable Energy Laboratory (NREL), and Professor Scott Anderson of the University of Utah and his research group.
 
Their work was featured in the April 30, 2018 issue of Chemical & Engineering News (C&EN) in an article titled "Cool fuel for hypersonic aircraft".
 
Catalyzed endothermic reactions of fuel components, such as selective dehydrogenation of alkanes to alkenes, can be used to cook down hypersonic jets without going on the ground. The team developed a new way to catalyze such reactions using surface-supported clusters consisting of just a handful of Pt atoms.
 
Previous research by the team showed that grouping platinum atoms into 7-atom clusters led to the highest catalytic activity toward dehydrogenating ethylene, whereas for selectivity it’d be preferred that it instead desorbs from the catalyst. High activity is the reason why these platinum-based clusters were prone to deactivation, mainly by getting covered with carbon-based gunk (coke) – a product of full dehydrogenation. The research team set out to determine ways to improve the lifespan of their catalyst, and boost the selectivity for the optimal cooling performance.
 
To do so, the researchers added boron gas to their platinum clusters. Through a tight combination of theory and experiment, the researchers found the boron-platinum clusters had fewer and weaker binding sites for ethylene, and thus desorb it instead of dehydrogenating further. Coke does not build up on these modified catalysts after multiple cycles of temperature programmed desorption/reaction. Hence, the boron-platinum clusters maintained catalytic activity over a longer period of time. 
 
The researchers suggest that changing the amount boron added may allow scientists to fine-tune the activity and the lifespan of their catalysts.
 
A theoretical and computational chemist, Alexandrova joined the UCLA Department of Chemistry & Biochemistry faculty in 2009. Her honors include a 2016 Fulbright Fellow, a 2015 Rising Star Award of the WCC American Chemical Society, a 2014 NSF Career Award, and a 2013 Sloan Research Fellowship. The focus of her laboratory is computational and theoretical design and multi-scale description of new materials.
 
Ha received a Ph.D. in chemistry at UCLA in 2017. In 2016, she was selected for a prestigious DOE Office of Science Graduate Student Research Award (SCGSR) award to work at the National Renewable Energy Laboratory (NREL) where her research focused on extended surface catalysts such as Pt-Ni and Pt-Co NW for oxygen reduction reaction (ORR), in order to understand the effect of a Pt-M oxide interface on ORR reactants.  
 
To learn more about the Alexandrova group’s research, visit their website.
 
The research was funded by the US Air Force.
 
Many thanks to Joseph Ong for his contribution to this article.