Christopher Paolucci joined the Department of Chemical Engineering at the University of Virginia as a tenure-track Assistant Professor
in Fall 2018. He received his BS in Chemical Engineering from the University of Notre Dame in 2012, and his PhD in Chemical Engineering from the University of Notre Dame in 2017 under the guidance of William F. Schneider (2012-2017) and as a visiting scholar
at Purdue University under the guidance of Fabio Ribeiro, Nicholas Delgass, and Rajamani Gounder (2015). He continued his research in machine learning guided materials screening between fall 2017 and spring 2018 in the group of Jens Nørskov and Thomas Bligaard
at Stanford University. Chris’ expertise is the application of electronic structure calculations, molecular dynamics, Monte Carlo simulation, and kinetic modeling to problems in materials science and heterogeneous catalysis. His main research areas of interest
are catalyst stability and catalyst dynamics under reaction conditions. He received the ACS PRF Doctoral New Investigator award in 2021 and the NSF CAREER award in 2022. He served as a director of the Catalysis and Reaction Engineering Division of AIChE from
2019-2021 and is currently the president of the Southeastern Catalysis Society.
Catalytic reactions are often defined by their structure sensitivity, which is determined by the molecular identity of their active sites. Here, as contrasting
examples, I discuss a highly structure sensitive catalyst-reaction system, and a structure-insensitive system, and use a combination of experimental and computational analyses to describe the underlying physics that results in these two disparate outcomes.
Nitrous oxide (N2O), a global warming gas, is an undesirable product formed within diesel after-treatment systems. Advances in combustion engines
have led to a decrease in waste heat and overall exhaust temperature. However, at these low temperatures (400 K – 600 K) N2O is formed over the diesel oxidation catalyst (DOC) unit of the aftertreatment system. The DOC is typically composed of oxide
supported Pt, or Pt and Pd alloys, and its primary role is to oxidize NOx, CO, and uncombusted hydrocarbons. The molecular details of N2O formation and its structure sensitivity
are debated. Here, we use density functional theory (DFT) calculations for N2O formation and accompanying reactions over different model Pt facets to gain a molecular understanding of the reaction over model Pt DOCs. Our predictions were tested
using transient kinetic experiments and a microkinetic model was developed using a combination of DFT and experimental data. Taken together, our results indicate that the step-edge sites of Pt nanoparticles are the active sites for N2O formation,
and the population of these sites is strongly dependent on particle size. More broadly, we anticipate that low temperature N2O formation could be used as a structure-sensitive probe to count active site populations for other reactions.
Silver nanoparticles (NPs) are commercial catalysts used for selective oxidation of ethylene to ethylene oxide (EO). Upon exposure to ethylene and O2,
or O2 alone, numerous studies indicate that the Ag surface reconstructs, however, the surface structures formed remain debated. Here, we use DFT sampling of potential energy surfaces implemented in the Fast Learning of Atomistic Rare Events (FLARE)
code to generate a Gaussian Process (GP) interatomic potential descriptive of O-Ag interactions. Enabled by the GP potential, molecular dynamics and Monte Carlo simulations show that partially oxidized Ag surfaces promote the formation of peroxide surface
intermediates that are surprisingly more selective to ethylene oxide than their monatomic counterparts. Consequently, gas conditions that either completely reduce or over-oxidize Ag surfaces lead to catalyst deactivation, while intermediate conditions result
in disordered surfaces that suppresses structural differences between nanoparticle facets. These phenomena may explain the observed structure-insensitivity of ethylene epoxidation under some gas conditions.
