Spring 2022

Departmental Seminars

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January 10, 2022
10:30 AM
EB1 Room 1011
Dr. Peter Vekilov
University of Houston
Often, available data on the reaction mechanisms are employed to model and engineer the rates and outcomes of chemical processes. We enforce a flow of information in the opposite direction. I will discuss two examples, in which we use reaction rates measured under carefully controlled conditions to deduce intimate details about the molecular motions that manifest macroscopically as aggregation and crystallization.The accumulation of fibrils and plaques of the amyloid beta peptide is a hallmark and the likely cause of Alzheimer’s disease and related neuropathies. Ab fibrillization is an exceedingly complex process, in which the conformational transformations of the peptide chains integrate with fibril nucleation, growth, fractionation, and branching to form a network of intertwined events. We posit that the tips of the growing fibrils are the Achilles heel of fibrillization to be targeted by additives that may rise to potential Alzheimer’s drugs. We pioneer the use of time-resolved in situ atomic force microscopy to monitor the responses of the fibril growth rate to the thermodynamic driving force and the presence of a denaturant. The AFM results, concurrently with molecular simulations, advocate that a complex comprised of three or four peptide chains in non-native conformations crowns the fibril tips and governs the rate of incorporation of incoming peptide monomers. We show that drug induced restructuring of this frustrated complex may be a successful strategy to stunt fibril growth.Molecular crystallization rests at the core of physiological, geological, and industrial processes. Attempts to predict a priori crystal growth rates and their anisotropy, which control the sizes and aspect ratios of the crystal populations, often fail owing to the poor understanding of the constituent molecular processes. Time-resolved in situ AFM measurements, complemented by all-atom MD modeling, reveal that the egress of a solute molecules into a crystal growth site, a kink, proceeds in two steps. The stability of the intermediate state is administered by the solvent – solute – kink interactions. The proposed two-step scheme of molecular incorporation presents a new paradigm for solution crystallization that may contribute to understanding crystallization in nature and expedite the selection of solutes and solvents in the crystallization process design of organic pharmaceuticals and advanced materials.
January 19, 2022
10:30 AM
EB1 Room 1011
Dr. De-En Jiang
University of California, Riverside
My group is interested in both knowledge- and data-driven design of functional molecules and materials in chemical separations, nanocatalysis, and electric energy storage from a computational perspective. In this talk, I will first discuss several design approaches to tune and control pore size to achieve desired gas separation performances via graphene membranes. Concepts of ion-gating and entropy selectivity will be demonstrated via molecular simulations. Next, I will talk about porous carbonaceous materials for carbon capture; here we show that the 77K-N2-adsorption isotherms of porous carbons can be used as direct input to train convolutional neural networks for prediction of gas separation performance and to explore much broader porosity space. In the third topic, I will show an exciting progress in atomically precise metal-hydride nanocluster catalysts where the challenge to locate the hydrides was addressed by deep neural networks. In each of the studies, one will see a close interplay between computation and experiment, demonstrating that computation or an experiment in silico is now a valuable tool to drive advances chemical separations and catalysis.

January 19, 2022
5:00 PM
FWH Room 2336
Dr. Jason Smith
IP Group, Inc.
One of the most compelling challenges for government and society is the translation of billions of dollars in government research investment into benefits for humanity. Often referred to as the valley of death, the complex interface of knowledge, expertise and motivation between academia and the commercial world is undergoing a period of rapid transformation. On the front line, there is a critical need for individuals that speak the language of both sides that are motivated to bridge the gap. This isn’t an end of career look back at how we figured it all out. This is a mid-career snapshot likely to generate as many questions as answers. I plan to share how I wound my way from a postdoc to the valley of death, why I’m more excited than ever about the potential of NC State scientists to change the world, and some lessons learned along the way. I understand there will also be free pizza!

January 24, 2022
10:30 AM
EB1 Room 1011
Dr. Vibha Kalra
Drexel University 
Rechargeable batteries with conversion type electrodes are attractive due to their ability to achieve higher capacity through multi-electron transfer reactions. Elemental sulfur is one of the most interesting materials amongst all conversion-based cathodes because of its high theoretical capacity (~1675 mAh/g – 5-10-fold higher than Li-ion batteries), natural abundance, non- toxicity, and cost-effectiveness. In this talk, I will present our group’s research on integrating material design and fabrication, in-operando and postmortem spectroscopy, and device assembly and testing to study and develop next generation lithium-sulfur batteries.
January 26, 2022
10:30 AM
EB1 Room 1011
Dr. Artem Rumyantsev
University of Chicago
Electrostatically driven phase separation in solutions of the oppositely charged polyelectrolytes (referred to as complex coacervation) and solutions of polyampholytes (called self-coacervation) is currently viewed as the basic physical model describing intracellular organization and the formation of membrane-less organelles. Coulomb attractions between the opposite charges within the polymer-rich phase are due to their positional correlations, and statistical physics of ionic polymers can be fruitfully applied to gain valuable insight into these phenomena. First, I will focus on how the equilibrium and dynamics properties of polymer-rich complex coacervate phases are affected by (i) salt concentration, (ii) solvent quality, (iii) stiffness of polyelectrolytes, (iv) their incompatibility, and (v) sequence of ionic and neutral monomers in them. I will then discuss the conformational behavior of single-chain sequence-defined polyampholytes modeling intrinsically disordered proteins (IDPs). For polyampholytes/IDPs with a non-zero net charge, the interplay between sequence-dependent correlation-induced attractions and bare Coulomb repulsions results in different conformations ranging from spherical globules to strongly stretched chains, including “necklaces” of various structures containing several smaller globules connected by the extended strings.
January 28, 2022
10:30 AM
EB2 Room 1021
Dr. Wentao Tang
Shell Global Solutions (U.S.) Inc.
Optimally controlling large-scale interconnected chemical plants, or process networks, is a bottleneck problem in the theory and practice of contemporary process control. This demands a structured and scalable approach with effective methods of decomposing process networks into constituent subsystems and coordinating the controllers for subsystems. With the perspective of network science, community detection is proposed to reveal the underlying block structures in the network representations of control systems, which generates decompositions with reduced computational cost and retained control performance. For subsystem controller coordination, distributed optimization is adopted to guarantee the optimal solution for the monolithic system, and efficient and real-time implementable algorithms are developed to overcome the computational challenge of applying distributed optimization in control. The methods are applied to multiple benchmark processes, and future directions are discussed.
January 31, 2022
10:30 AM
EB1 Room 1011
Dr. Mitchell Wang
Northwestern University
The Wang Lab develops new methods for characterizing polymers to address today’s challenges, with the philosophy that new methods for seeing and measuring often open completely new fields of application and fundamental study. As an example, we use single-molecule super-resolution microscopy to image samples in their native environments and watch them as they evolve. We have applied this to fundamental questions in polymer self-assembly, mechanics, and dynamics, enabling engineers to control where and when something happens in a polymeric material. For example, we have recently answered the question of what a polymer looks like in a solid material, for the first time. Separately, we are developing high-throughput characterization methods for mechanical properties in soft materials. These techniques can change the way materials are designed in the era of AI and machine learning.BIOMuzhou “Mitchell” Wang received his undergraduate degree in Chemical Engineering from Caltech, where he worked with Prof. Julia A. Kornfield. He then went to MIT for his Ph.D. studies, joining Prof. Bradley D. Olsen as his first student. In the Olsen group, he used experiments and simulations to understand the dynamics of entangled block copolymers. He continued his work as a National Research Council postdoctoral fellow at the National Institute of Standards and Technology, where he worked on super-resolution optical microscopy of nanofabricated polymer materials with Dr. Jeffrey W. Gilman and Dr. J. Alexander Liddle. He started his group at Northwestern in 2017, where he has been recognized with a number of honors including an NSF CAREER award and an APS DPOLY/UKPPG Lectureship.
February 7, 2022
10:30 AM
EB2 Room 1021
Dr. David Koshy
Stanford University
Electrochemical CO2 reduction (CO2R) has attracted significant interest as a route for producing carbon-based fuels and chemicals using renewable electricity and operating at ambient conditions. Due to the challenging kinetics of CO2R, electrocatalysts are needed to achieve reasonable rates for products like carbon monoxide (CO), ethanol, or ethylene.Ni, N-doped carbon (Ni-N-C), a material consisting of nitrogen and nickel dopants in a graphitic carbon matrix, has recently been reported as an active and selective catalyst for CO2 reduction to CO. Ni-N-C catalysts are hypothesized to be “single atom catalysts” which contain atomically dispersed, nitrogen-coordinated NiNx sites that are structurally similar to molecular Ni complexes. However, the search for evidence to support this this active site hypothesis has not yielded proof that these NiNx sites exist or that they are CO2R active sites.This talk describes the use of a wide variety of complementary characterization techniques to obtain a holistic understanding of the CO2R active site on Ni-N-C materials. Specifically, kinetic measurements were combined with physiochemical characterization techniques including electron microscopy, X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, mass spectrometry, electron energy loss spectroscopy, and Mössbauer spectroscopy. This multimodal approach revealed that NiNx sites are likely CO2R active sites and that Ni2+ is present in a distorted square-planar geometry with nitrogen coordinating atoms.Next, the thermal stability of these Ni-N-C materials provided a unique opportunity to directly compare the conversion of CO2 to CO under an electrochemical driving force (CO2 reduction) and a thermochemical driving force (reverse water gas shift, RWGS). This comparison showed that the same Ni-N-C powder could catalyze both electrochemical CO2R and thermal RWGS, demonstrating a direct connection between catalytic activity across disparate reaction environments. To strengthen this comparison, the driving forces for the two reaction systems were quantitatively compared. This analysis revealed that the higher intrinsic activity of Ni-N-C in the electrochemical environment likely originates from lowered reaction barriers at the electrified interface.In summary, this research demonstrates that Ni-N-C materials exhibit unique catalytic activity that intersects many subdisciplines of catalysis science: containing molecular-like active sites in a heterogeneous framework and catalyzing analogous chemical transformations in both electrochemical and thermal reaction conditions.
February 9, 2022
10:30 AM
EB1 Room 1011
Dr. Christopher J. Bartel
University of California, Berkeley
Countless technologies are enabled by the development of improved solid-state materials (e.g., layered oxides for Li-ion battery cathodes, nitride semiconductors for light-emitting diodes, and hybrid perovskites for photovoltaics). The transition to an energy portfolio free of fossil fuels demands that the materials used for these technologies become cheaper, more efficient, and more sustainably sourced. Quantum chemistry has emerged as a useful tool to computationally prototype new candidate materials before they are tried in the lab. However, the efficient identification of good candidates is made daunting by the broad diversity of chemistries and structures that can be realized in the solid state. This vast design space has motivated the emergence of materials informatics, where computational chemistry and machine learning meet to accelerate the discovery of new materials with emergent properties. No matter the application of interest, materials discovery efforts hinge upon on an essential question — is this candidate material stable? In this talk, I will discuss how I address this question using simple and interpretable models called descriptors. Finally, I will show how we can move beyond the question of stability and toward a new paradigm of predictive materials synthesis.
February 11, 2022
10:30 AM
EB2 Room 1021
Dr. Robert Warburton
Yale University
In the transition away from fossil fuels, high-performance electrochemical devices are needed to realize new routes to transportation, energy storage, and chemical synthesis solutions. Understanding the electrochemical redox reactions at the electrode–electrolyte interface in such systems is therefore essential toward the rational optimization of electrochemical devices for energy-critical applications. First principles theoretical calculations, such as density functional theory (DFT), can be a useful approach to elucidate the atomic-scale structure and reactivity of interfaces in electrochemical systems. In this talk, I will describe the application of such computational methods to the analysis of interfacial thermodynamics, as well as the impact of interfacial electric fields on desolvation and electrocatalytic reactivity. These phenomena will be explored using atomistic models, with specific examples applied to solid-state lithium-ion batteries, vibrational probes of local electric fields at electrode–solution interfaces, and proton-coupled electron transfer reactions at graphite-conjugated molecular catalysts. In combination with accompanying experimental measurements, these studies shed new light on critical interfacial processes in electrochemical systems.

February 14, 2022
10:30 AM
EB1 Room 1011
Dr. Julie Rorrer
Massachusetts Institute of  Technology
The rapid global consumption of single-use plastics has caused an unsustainable accumulation of plastic waste in landfills and the environment. Unfortunately, current mechanical recycling methods are expensive and produce lower-quality products. New strategies in targeted chemical upcycling of waste plastics offer unique opportunities for selective depolymerization of polyolefins to higher value chemicals under milder conditions than thermal deconstruction or pyrolysis. Inspired by recent developments in the depolymerization of lignin, we turned to the method of hydrogenolysis to break the strong C-C bonds in polyolefins. This talk will cover our efforts in identifying a class of ruthenium-based materials as active and selective heterogeneous catalysts for the depolymerization of polyolefin waste, catalyst support modification strategies to further improve selectivity towards processible liquid alkanes, and new frameworks for the chemical upcycling of waste plastics and complex mixed waste streams to enable a circular carbon economy.
February 16, 2022
10:30 AM
EB1 Room 1011
Dr. Ivan A. Moreno-Hernandez
University of California, Berkeley
Electrochemical materials are required to store renewable energy and sustainably couple the chemical and energy industries. This talk will focus on advancements in both the discovery of new electrochemical materials with improved performance and the development of new techniques to observe the structural dynamics of electrochemical materials. We will first discuss the discovery of an earth-abundant class of electrocatalysts that are thermodynamically stable for the oxygen evolution and chlorine evolution reactions in acidic electrolytes. Our discussion will then focus on the development of a redox-mediated approach to control electrochemical reactions in liquid cell electron microscopy, a technique that allows reactions to be observed at near-atomic resolution over time.
February 21, 2022
10:30 AM
EB1 Room 1011
Dr. Sheima Khatib
Texas Tech University 
Methane, derived from shale gas, is a cheap and abundant molecule that can be used as a building block in the chemicals manufacturing industry, but instead, large quantities of stranded shale gas are being flared due to lack of existing infrastructures for its transportation to centralized processing facilities. The catalytic valorization of methane to aromatics and hydrogen, by the one-step non-oxidative methane dehydroaromatization reaction (6 CH4  C6H6+ 9H2), MDA, is an attractive route for natural gas upgrade since it can be implemented at the gas source, offering the opportunity for development of modular technology for distributed manufacturing of aromatics while reducing processing and transportation costs. Our group is carrying out a systematic study of this catalytic process with the aim of answering long-standing fundamental questions related to MDA chemistry which will enable development of strategies to mitigate the technological challenges associated with MDA.
Zeolite-supported molybdenum catalysts are the most effective MDA catalysts studied so far, but they do not possess conversion and stability requirements for commercialization. Molybdenum carbide species are thought to constitute the active sites for MDA and are formed when the zeolite-supported Mo oxide species in the as-prepared catalysts are exposed to methane in the first minutes of reaction. In this talk I will describe how our group has discovered that the activation protocol employed to form the active molybdenum carbide sites plays a critical role in catalyst stability. I will also present how our studies on the effect of the zeolite acidity employing in situ/operando X-ray absorption spectroscopy suggest that the structure of local environment of the as-prepared molybdenum oxide sites does not affect the catalyst performance, underpinning the importance of controlling the carbide formation step. I will also discuss our most recent results indicating that the addition of small amounts of a second transition metal promoter, such as cobalt and nickel, employing our new activation protocol results in further enhancement of catalyst stability.
February 23, 2022
10:30 AM
EB1 Room 1011
Dr. Dohyung Kim
Stanford University  
There has been growing interest to drive chemical reactions via the direct use of renewable electricity to address sustainability challenges. The success of the approach rests on the use of the right materials to efficiently catalyze electrochemical reactions. Thus, there have been intense efforts to engineer catalyst materials whose surface contains the desired active sites. Despite the success, there is still much room for improvement in the field of electrocatalysis. However, it is not because of our limited advances in the synthesis of materials and their use as catalysts. It is because of how we typically view catalytic reactions at the solid-liquid interface that often lacks consideration of the liquid phase (e.g., solvent molecules, double-layer ions). The “BEYOND SURFACE” approach that not only recognizes the presence and role of liquid phase components but alters their characteristics to facilitate chemical reactions will bring the necessary advances to progress beyond the performance levels achieved to date. In this talk, two examples of the “BEYOND SURFACE” approach are presented for electrocatalytic reactions of renewable carbons, CO2 and biomass. The first example concerns the discovery of a unique interfacial configuration on the surface of colloidal nanoparticles, that is the Nanoparticle/Ordered-Ligand Interlayer (NOLI). Its operation as a catalytic pocket for CO2 reduction by the synergistic act of the nanoparticle surface and surface ligands hovering above suggests a new route to promote reactions by tuning the electric double layer using materials. The other example presents the need for a better understanding of solvent molecule behavior at electrochemically active interfaces. During electrooxidation of biomass-derived polyols, it is shown that the interaction between the Pt surface and surrounding water eventually leads to its surface oxidation limiting catalytic activity at fixed potential conditions. Thus, a unique method so-called electrochemical potential cycling is devised that continuously cycles between oxidative and reductive potentials exploiting the short-lived high activity state of Pt nanoparticles otherwise difficult to maintain under typical conditions. These studies highlight the complexity of electrochemical interfaces and the potential of thinking beyond the surface for electrocatalytic reactions.
February 28, 2022
10:30 AM
EB1 Room 1011
Dr. Fang Liu
Stanford University
High-energy density batteries will play a remarkable role in hurdling global climate change. My research focuses on the fundamental understandings of their electrochemical reaction mechanisms and the design of materials, protocols, and characterization tools to enable their safe operations over long-term use. First, I will discuss about the previously overlooked dynamics of detached lithium metal filaments during battery operations. This discovery leads to the recovery of lost capacities in lithium-metal batteries and enables fast charging in lithium-ion batteries. Next, I will introduce a characterization tool for the on-board monitoring of battery health based on pressure evolutions. In addition to capturing the early signs of battery failure, this pressure sensing system offers new insights into the battery degradation process. Overall, the combination of fundamental study and the rational design of materials/protocols/characterization tools opens broad opportunities toward a clean energy future.
March 7, 2022
10:30 AM
EB1 Room 1011
Dr. Lynden Archer
Cornell University  
March 21, 2022
10:30 AM
EB1 Room 1011
Dr. Heath Ledger
University of Alabama
March 28, 2022
10:30 AM
EB1 Room 1011
Dr. Levi  Thompson
University of Delaware
April 4, 2022
10:30 AM
EB1 Room 1011
Dr. George Jackson
Imperial College London
April 5, 2022
3:00 PM
EB1 Room 1011
Dr. George Jackson
Imperial College London
April 11, 2022
10:30 AM
EB1 Room 1011
Dr. John Brady
California Institute of  Technology
April 25, 2022
10:30 AM
EB1 Room 1011