Porous Materials for Electrochemical Applications

Understanding selectivity and durability of porous water-splitting catalysts in seawater

Faculty Mentor: Kevin C. Leonard

Research Overview: Direct electrolysis of seawater shown in the picture to the right would enable remote energy storage and potable water generation when used in conjunction with a fuel cell. However, challenges with corrosion, precipitation of solids, and selectivity between chloride oxidation and water oxidation must be overcome. The Leonard Lab has significant experience developing porous electrocatalysts for the water-splitting reactions. In this project, students will investigate synthesizing and characterizing seawater splitting catalysts using our previously developed synthesis method. In addition, students will investigate porous corrosion protection coatings to enhance lifetime and learn how to evaluate potential materials using stability, performance, and cost-effectiveness metrics.

Undergraduate Opportunities and Outcomes: Students will have the opportunity to learn about electrochemistry and electrocatalysis – a topic typically not covered in detail in traditional undergraduate curriculums. In addition, they will learn catalyst synthesis and characterization techniques, including electron microscopy (e.g., SEM) and x-ray characterization techniques (e.g., XRD and XPS). Undergraduate students will learn how to perform electrochemical experiments using a potentiostat and apply concepts taught in undergraduate courses, including mass transfer, kinetics, and electrical physics.

Porous Materials for Bioengineering Applications

Probing the interaction and potential toxicity of porous materials

Faculty Mentors: Prajna Dhar (Lead); Alan Allgeier (Collaborator)

Research Overview: Fundamental understanding of the interaction of biologically relevant molecules (lipids, proteins, antibodies, pharmaceuticals) with solid particles is critical to understanding potential bronchial dysfunction associated with respirable particles as shown in the figure to the right and to understanding parenteral formulations employing antibody / adjuvant adsorption. The Dhar Lab studies molecular interactions at interfaces with applications in pharmaceutical and biological systems, focusing on mechanical and morphological changes in lipid-protein mixtures due to interactions with various porous materials, while the Allgeier Lab studies adsorption phenomena utilizing time-domain nuclear magnetic resonance (NMR) measurements and other techniques. Using biophysical and analytical techniques unique to both labs (such as an interfacial viscosity measurement device coupled to a fluorescence microscopy, high resolution imaging techniques such as AFM, and low-field NMR), we propose to measure changes in model membrane structures when they interact with porous materials. By working with other groups synthesizing these materials, we propose to study the impact of soft vs. hard porous materials on biological systems, particularly cell membranes, in an effort to access the cytotoxicity of these novel materials.

Undergraduate Opportunities and Outcomes: Students will have the opportunity to learn about and personally utilize advanced scientific instrumentation including biophysical tools such as a Langmuir trough, custom designed to be coupled with fluorescence microscopy and a low-field NMR to characterize porous material interactions with biomolecules. Further, they will learn: (a) to interpret data, elucidating the basics of biomolecule / porous particle interactions, (b) the significance of health impacts of our studies, and (c) fundamentals of both biomedical and chemical engineering fields where concepts learned in their coursework will be applied in a research setting (e.g. thermodynamics & fluid mechanics).

Control and evaluation of porosity in hydrogels

Faculty Mentors: Stevin Gehrke (Lead); Alan Allgeier (Collaborator)

Research Overview: Hydrogels are crosslinked networks of hydrophilic polymers that can absorb many times their mass in water. This behavior leads to their technological applications as diverse as superabsorbents in consumer products and cell-supporting scaffolds in regenerative medicine. New methodologies for hydrogel synthesis have rapidly expanded in the past 20 years to improve the mechanical performance of the hydrogels, refine their ability to control permeation of bioactive molecules in biomedical applications, or to enable their use in biomedical applications with living cells and tissues or be amenable to synthesis by 3D printing. While the performance of the gels is directly tied to the network structure formed at synthesis, the characterization of the structure is difficult as there are multiple relevant length scales of structure from the nanometer to macroscopic levels that are determined by the synthesis method as shown in the figure. Thus, understanding synthesis-structure-property relations is central to advances in the field and developing new methods to characterize the network structures is also necessary to make such advances. The Gehrke Lab is centered on the synthesis of novel polymer networks and development of structure-property relationships using a variety of instrumentation. Students will work with the Allgeier Lab on the use of low-field NMR techniques to characterize network dimensions and porosities.

Undergraduate Opportunities and Outcomes:  Students will learn broadly significant methods of polymer synthesis and characterization focused on biomedical applications of these materials. They will carry out biopolymer functionalization and network synthesis by a variety of methods and will use high precision mechanical instrumentation to characterize the hydrogels and advanced theories to develop synthesis-structure relationships. They will also use low-field NMR to further characterize the network structure by a cutting-edge approach that has the potential for rapid screening of structure as a function of synthesis parameters. The work will advance development of new materials for biomedical application in drug delivery and tissue engineering. Students thus will learn polymer synthesis, materials characterization, use of theories to infer molecular parameters from data and biomedical application of hydrogels.

Porous Materials for Chemical Engineering Applications

Supported Ionic Liquid Phase (SILP) Materials for Separations & Catalysis

Faculty Mentors: Aaron Scurto (lead); Mark Shiflett, Alan Allgeier (Collaborators)

Research Overview:  Separation of gases is required in a variety of industrial fields. Catalysis with soluble acids, bases, or organometallic complexes has been utilized for many chemical transformations with high reaction rates and selectivity. However for industrial implementation of either of these processes, the materials and products must be easily (economically) separated and recycled and should be based upon modern principles of “green”/sustainable chemistry and engineering. A new system has been proposed called Supported Ionic Liquid Phase (SILP) materials and has been applied to a number of different catalyzed reactions and separations. Here, a non-volatile and molecularly-tunable ionic liquid (IL) is coated at the micro-/meso-scale on a solid support as shown in the figure to the right. The IL phase provides the material that selectively separates different gas mixtures.  For reactions, the IL sequesters a soluble catalyst and influences the reaction. The Scurto lab is developing a comprehensive fundamental understanding of the physical and chemical properties of ILs for separations or catalyzed reactions for rational design of complete systems.  Students will learn a variety of experimental and analytical techniques that will be very pertinent to their future careers in engineering.

Undergraduate Opportunities and Outcomes:  ILs will be synthesized for specific tasks. The physical properties (density, viscosity, diffusivity, thermal conductivity) will be measured. The liquid and gas solubilities (phase equilibrium thermodynamics) in ILs will be explored. Different techniques will then be used to coat the pores with and without catalysts. These coatings will then be characterized. Either of two different applications will be explored: (1) gas separations and (2) catalyzed reactions. The fundamental studies of SILPs will utilize student’s skills in a variety of fields from chemistry, thermodynamics, kinetics, materials science, and mass transfer. Students will evaluate scaled-up processes to look at economics and sustainability of the process through life-cycle assessment (LCA).

Separation of azeotropic refrigerant mixtures using porous media

Faculty Mentors: Mark Shiflett (Lead), David Corbin (Collaborator)

Research Overview: Hydrofluorocarbons (HFCs) are commonly used as refrigerants, blowing agents, and fire extinguishants; however, new concerns over the high global warming potential of these gases has led to recent legislation requiring the phasedown of these substances.  Many refrigerants are composed of mixtures that form azeotropes that cannot be separated using fractional distillation techniques. For this reason, new separation processes will be required and a new approach is using porous materials to separate refrigerants based on difference in adsorption and molecular size. The Shiflett lab is developing a variety of new porous materials such as zeolites and carbons for the separation of azeotropic HFC mixtures such as R-410A, which is composed of 50 wt% difluoromethane (HFC-32, CH2F2) and 50 wt% pentafluoroethane (HFC-125, CHF2CF3). Solubility and diffusivity data are being measured using a gravimetric microbalance, heats of sorption are being measured with a calorimeter, and a breakthrough apparatus is testing mixed gases for collecting basic data for scaling-up the process. The pore size of the zeolites are being designed such that the smaller HFC-32 will adsorb and the larger HFC-125 will pass through the material as shown in Fig. 6; therefore, providing a highly selective separation.

Undergraduate Opportunities and Outcomes:  The REU students will learn about refrigerants, the phasedown of these high global warming gases, and porous media such as zeolites and carbons. Students will become familiar with how to characterize the surface of materials using a Micrometrics ASAP instrument as well as how to operate and analyze data using a gravimetric microbalance and calorimeter. Students will also learn how to model the results using both Ideal Adsorbed Solution Theory (IAST) and Real Adsorbed Solution Theory (RAST) to predict mixture adsorption. They will also learn how to scale-up new technologies from laboratory to pilot-scale and how products are patented and commercialized.

New Strategies to Renewable Polyamide Monomers

Faculty Mentors: Alan Allgeier (Lead)

Research Overview: A sustainable future for the chemical industry necessitates the use of renewable sources of carbon over utilization of fossil resources. Prior studies in biomass valorization focus on the selective removal of excess oxygen from cellulose to achieve diol and diacid monomers as shown in the figure. We hypothesize that a number of these platform molecules may be selectively converted to monomers for polyamides (e.g. Nylon 6,6). Indeed, the American company Celanese operated a large-scale process for making 1,6-hexanediamine in the 1970s using a porous nickel catalyst. The process was eventually shuddered because the reaction was not sufficiently selective. Additionally, the process was not economically viable, but it does provide a rational starting point for discovery of improved catalysts. To address the hypothesis, the Allgeier lab is developing shape selective catalysts, which prevent the formation of secondary amine byproducts. Zeolites are microporous catalysts that can host nickel and platinum cations in their cages such that only one molecule can fit at a time. We expect this shape selectivity will limit secondary amine formation, following precedent for methylamine processes.

Undergraduate Opportunities and Outcomes: Students will learn techniques of catalyst preparation including ion-exchange for zeolite synthesis. This encompasses preparing metal solutions, treatment of purchased zeolites, and high-temperature processing. Following catalyst synthesis, students will utilize pressure reactors for conducting amination reactions using ammonia. These systems are scaled-down versions of real industrial reactors and include computer control and design-for-safety attributes. When promising candidates are identified, students will have an opportunity to utilize advanced characterization tools such as X-ray diffraction, X-ray fluorescence, and solid-state NMR. These characterization tools enable an understanding of structure-performance correlations and facilitate catalyst optimization.

Tunability of surface reactivity within pores – Heterogeneous catalysis during plastics’ conversion

Faculty Mentor: Ana Morais (Lead)

Research Overview: The conversion kinetics of waste plastics, such as polystyrene (PS) as shown in the figure to the right, is highly limited by mass and heat transfer. PS is an example of a non-porous, insoluble polymer in most conventional solvents and highly viscous at temperatures greater than the melting point. These properties are responsible for heat and mass transfer issues during the conversion process. One possible route to improve conversion kinetics is to exploit the use of supercritical CO2 (scCO2) for PS deconstruction in conjunction with heterogeneous catalysts. The Morais lab studies how scCO2 interacts with the polymers to reduce its melting temperature and how this interaction changes the surface reactivity within the solid catalyst pores, reaction kinetics and activation energy, coke deposition, and consequential catalyst deactivation. The studies will be complemented with investigations of the extent to which (i) how the melting temperature of the polymer decreases with the presence of scCO2 and (ii) how the addition of scCO2 at varying conditions impact the rate of PS depolymerization, final polymer conversion, olefin yield, selectivity and molecular weight distribution. The Morais lab pays particular attention to the kinetics of coke formation and how scCO2 can reduce catalyst plugging and improve catalyst longevity during PS depolymerization. The knowledge gained will lead to a new framework for developing plastics’ conversion processes using a wide range of chemistries.

Undergraduate Opportunities and Outcomes: Students will engage in a variety of activities, ranging from research training in high-pressure reactions, operational conditions optimization, material characterization, and kinetic modeling. Students will receive training in a multi-disciplinary approach involving reaction engineering and chemistry.

Thermochemical conversion of municipal sludge to produce porous biochars

Faculty Mentors: Susan Stagg-Williams (lead), Belinda Sturm (Collaborator)

Research Overview: Wastewater treatment plants (WWTPs) are located around the globe and are vital for removing pollutants from water that will eventually be discharged as shown in the figure to the right. These WWTPs produce a solid waste as part of the sewage treatment process. The biosolids (municipal sludge) that are produced are typically applied as a fertilizer or disposed of in landfills. However, both of these practices are not sustainable.  Land application of municipal sludge will likely be strongly regulated or prohibited in the near future as there is a growing concern about health and safety aspects including residual materials leaching into the soil. Disposing of municipal sludge in landfills is not a permanent solution due to diminishing landfill space and the increasing cost to the WWTP. One possible solution is to utilize thermochemical conversion techniques on the municipal sludge to generate porous carbon-rich biochars that can be used in the environmental, energy, and fertilizer industries. The City of Lawrence has two WWTPs that will provide municipal sludge for the project. The Stagg-Williams lab is investigating the impact of the WWTP process on the product distribution and the properties of the products.

Undergraduate Opportunities and Outcomes: Students will conduct high temperature, high pressure conversion of waste biomass in Parr reactors. They will also learn about the tools to characterize the waste biomass, and the products CHNO contents will be used for determining elemental material balances, carbon efficiency, degree of heteroatom removal, and H/C and O/C ratios. ICP-OES analysis will be used for material balances, while determining mineral recoveries and selectivity. Simulated distillation of the biocrude will be achieved using TGA to monitor changes in distillate fractions. The composition of the biocrude will be determined using GC-MS. Students will focus on the material balance to determine the fate of different species during the hydrothermal liquefaction process.

3D printed Zeolite Passive Samplers for Detection of Perfluoroalkyl substances (PFAS)

Faculty Mentors: Felipe Anaya (lead), Mark Shiflett (Collaborator)

Research Overview: This project will use zeolite materials as the basis for developing passive samplers that can rapidly adsorb/desorb polyfluoroalkyl substances (PFAS) from aqueous samples, improving detection of these compounds in environmental systems. High-silica zeolites will serve as the fundamental PFAS-binding material, and a fundamental understanding of mechanisms will be elucidated. Students will perform experiments using 24 EPA-Priority PFAS compounds at 10 parts per billion (ppb) in water to test a variety of Beta (BEA), Faujasite (FAU), and Mordenite (MOR) zeolites. Perfluorooctanoic acid (PFOA), a PFAS compound of particular concern, is shown in the MOR zeolite structure in the figure to the right. The Shiflett lab has shown that these zeolites can remove 99+% of PFOA below 50 parts per trillion (ppt) compared with activated carbon, which removed only 70% in the same amount of time (5 minutes). The University of Kansas (KU) maintains a unique, highly-diverse collection of over 3,000 zeolites donated by the DuPont Company that will serve as the source for materials for the development of next-generation PFAS-zeolite binding technologies. Students will collaborate with the U.S. Army Engineers Research and Development Center Environmental Laboratory (ERDL EL) that will 3D print high-surface area zeolite polymer composite structures that will be tested at KU. The advantage of 3D printing is design freedom and easily deployable and retrievable zeolite structures that would not be possible using the granular zeolite powder. The 3D structures could then be deployed in environmental systems to concentrate PFAS compounds from surface waters, groundwaters, and wastewaters. The ability to improve the detection and location of PFAS compounds will protect the health of service members and military families at PFAS-impacted installations.

Undergraduate Opportunities and Outcomes: Students will learn about the issues of PFAS contamination and have the opportunity to interact with engineers at ERDL EL producing 3D printed passive samplers. Students will learn how to characterize porous materials using characterization tools such as BET, ICP-OES, TGA, SEM, and TEM and will perform sorption and kinetic studies with “real” water samples spiked with PFAS compounds for designing effective passive samplers. The students will meet weekly with chemists at KU performing molecular modeling (e.g., molecular-dynamic and Monte Carlo) to elucidate the fundamental binding mechanisms. A field trip to Fort Leavenworth and American Water Works is planned to provide an industrial perspective of the PFAS contamination issues.

Experimental and lab-scale simulation of multi-phase flow in porous media as an important tool for novel energy transition technologies

Faculty Mentors: Reza Barati (Lead) and Xiaoli Li (Co-Lead)

Research Overview: Energy transition topics such as CO2 capture, utilization, and storage (CCUS); hydrogen storage; usage of fuel cells; understanding of water resources with potential contaminants; and geothermal systems all directly or indirectly deal with multi-phase flow through porous media. The multiple phases of the fluids during such processes may involve vapor-liquid, vapor-liquid-liquid, and vapor-liquid-solid equilibria. The thermodynamics and the PVT models are the first step to characterize the fluids under the geo-stored conditions. Multi-phase flow equations in these systems may be coupled with chemical reaction models, mechanical shrinkage/dilation models, and/or heat transfer models depending on the complexity of the systems that is being investigated. Nano-sized pores have also shown significant impacts on phase- and flow- behavior of these fluids as shown in the figure. The Barati and Li labs are working on experimental and mathematical modeling of multi-phase flow in porous media. Our current focus is to improve the current understanding of multi-phase flow in porous media as applicable in CCUS, hydrogen storage, water resources, geothermal and fuel cells.

Undergraduate Opportunities and Outcomes: Students will have the opportunity to learn the fundamentals of flow in porous media coupled with other necessary physics and thermodynamics, depending on the system that will be investigated. They will receive an opportunity to run experiments, write codes, and conduct mathematical simulations relevant to their topic of interest. Students will further learn about interpretation of data (e.g., experimental and simulation), importance of energy transition discussions, and several of the most representative energy transition components while applying the fundamental topics that they have learned in courses such as thermodynamics, material balances, and mass transport.