Heterogeneous Catalysts are Dynamic Materials

Phillip Christopher Department of Chemical Engineering University of California, Santa Barbara The use of heterogeneous catalysts for important chemical conversions ranging from pollution mitigation to energy production relies on the design of active catalytic sites consisting of metal nanostructures supported on high surface area oxide materials. Key to design of these systems is identifying active site geometries and compositions that are optimized for desired catalytic reactions. These active sites vary in structural diversity from single atoms on oxide supports to unique interfaces between active metal species and oxide supports, making their characterization complex. This difficulty is further complicated because the exposure of oxide-supported metals to reactive environments can induce significant transformations in the structure of metal surfaces, support surfaces, and interactions between the metal and support. The dynamic transformation of catalytic structures induced by exposure to reaction conditions can cause significant changes in reactivity, requiring detailed in-situ analysis to identify active site motifs. I will highlight examples where we have exploited in-situ and ex-situ spectroscopy and microscopy to characterize heterogeneous catalysts at atomic scale, identify how reactive conditions modify active site structures, and relate this to catalytic performance. Phillip Christopher received his B.S. from University of California, Santa Barbara in 2006 and his M.S and Ph.D. from University of Michigan in 2011, all in Chemical Engineering. From 2011-2017 he was an Assistant Professor at University of California, Riverside. In 2017 he moved to the University of California, Santa Barbara where he is an Associate Professor in the Chemical Engineering Department and the Mellichamp Chair in Sustainable Manufacturing. He also currently serves as an Associate Editor for ACS Energy Letters. His research interests are in heterogeneous catalysis, in-situ characterization of the dynamic behavior of catalysts, and photocatalysis by metal nanostructures. Prof. Christopher has won various awards including the Young Scientists Award from the International Congress on Catalysis, Army Research Office Young Investigator Award, NSF Early CAREER Award, and the Early Career Award for Scientists and Engineers from the Army (ECASE-Army).