Participants will join an interdisciplinary team at the University of Central Florida to engage in hands-on research training. Each participant will partner with a faculty mentor and graduate student to address a specific research topic over the summer. Participants will be matched to projects based on their stated interests and match with potential mentors.
Project 1. Nanostructured materials for electrocatalysis (Dr. Xiaofeng Feng): The student electing this project will work closely with graduate students in the Feng lab to carry out research on the development and understanding of nanomaterials for electrochemical ammonia synthesis. They will synthesize and develop an understanding of the properties of metal nanomaterials used as catalysts for electrochemical reduction of nitrate (NO3−) to ammonia (NH3). When powered by solar- or wind-generated electricity, the electrochemical reduction of nitrate to ammonia provides a promising route for the recycling of nitrate from wastewater to mitigate related environmental problems. Furthermore, electrosynthesis of NH3 from NO3− in wastewater can enable a sustainable, carbon-neutral processes for ammonia production using renewable electricity. This project will focus on Cu-based nanomaterials, which are promising electrocatalysts for nitrate reduction. The scientific goals of this project are to synthesize Cu/CuO nanowires with different structures, morphologies, and oxidation states and to understand their effects on the activity and selectivity for nitrate electroreduction. The educational objectives are to expose the student to the science and engineering of nanostructured materials and their possible application for sustainable ammonia synthesis. The student will receive training in (i) synthesis of metal nanostructures; (ii) characterization of the nanomaterials using SEM, TEM, XRD, and XPS to understand their morphology, structure and chemical state, before and after electrochemical tests; (iii) evaluation of different electrocatalysts for nitrate reduction using linear sweep voltammetry (LSV), cyclic voltammetry (CV), bulk electrolysis, electrochemical-impedance spectroscopy (EIS), and Tafel analysis; (iv) quantification of the reaction products using gas chromatography (GC), nuclear magnetic resonance (NMR) spectroscopy, and spectrophotometric methods; and (v) integrating the catalysts into electrochemical flow cells and optimizing their performance for ammonia production. The students participating in this project will be trained in materials science and electrochemical catalysis in order to inspire and mentor the next generation of scientists and engineers for renewable energy technologies and sustainability.
Project 2. Monolith-supported nanocatalysts (Dr. Titel Jurca): This project aims at understanding the synthesis, characterization, and application of monolith-supported precious metal nanocatalysts. Research in the Jurca Lab is focused on the discovery of novel hierarchical catalyst frameworks and understanding their process- structure-property-activity relationships, with the goal of creating robust and reusable frameworks for hydrogenation reactions. To create these materials, the participating student will use a combination of hydro- and solvo-thermal methods, coupled with overcoating using atomic layer deposition (ALD) techniques– the result will be highly robust and reusable frameworks capable of exceptional catalytic performance. To that end, Ni-foam monolith catalysts will be tested both in batch, and in flow reactions for the hydrogenation of common moieties, for example, nitroaromatics, alkynes, alkenes, and imines (of increasing complexity). The nature of this work spans the range of materials synthesis and characterization — from reactor design and reaction processing to fine chemical and organic synthesis techniques and applications. The student will participate in our current focus on extending the methodology beyond Pd with Al2O3 overcoating. The goal is to create a library of Pd, Pt, Rh, and Ir supported catalysts with Al2O3, TiO2, ZrO2, and ZnO ALD overcoats and study their intricate structure-activity properties. The educational objective for participating students is to expose them to the correlated aspects of heterogeneous catalysts’ physical properties and their direct impacts on performance. A key outcome will be their understanding of how the choice of metals and overcoats, and their preparative routes will impact the reactivity and selectivity of the catalyst. At the hands-on level, the students will learn core techniques pertinent to nanomaterials synthesis, as well as requisite characterization techniques such as scanning electron microscopy and x-ray photoelectron spectroscopy. They will learn how to operate batch reactions and receive an introduction to flow-reactor design. They will be able to run reactions, isolate products through rotary evaporation, silica columns, prep-TLC, and acquire and interpret 1H nuclear magnetic resonance (NMR) spectra.
Project 3. Monitoring the efficiency and stability of 2D and ultrathin oxide film-based catalysts (Dr. Denisia Popolan-Vaida): The project in Popolan-Vaida’s laboratory focuses on understanding the catalytic properties and stability of novel two-dimensional (2D) nanostructured materials. The activity, selectivity, and stability of 2D catalysts and ultrathin oxide films towards production of chemicals with high industrial and technological relevance are investigated under realistic pressure and temperature reaction conditions. 2D materials, such as MoS2, WS2, hBN, and thin oxide-films, such as CeO2/Ce2O3, CuO, and ZnO, will be prepared via ALD or PVD in Banerjee’s and Vaida’s laboratories. The UGS will learn the process of loading these materials with defects or decorating them with base metal clusters of Cu, Fe, and Ni. The UGS will then explore reactions such as water gas-shift, CO and CO2 hydrogenation, using a newly- designed catalytic jet-stirred reactor (JSR) coupled with various analytical tools. The catalytic JSR provides well-defined residence times but average the gas-phase completely over spatial dimensions, in order to enable the most straightforward comparison with chemistry models. Controlled amounts of reactants will be injected by means of regulated mass flow controllers into the catalytic JSR held at atmospheric pressure and well-defined temperatures by a PID controlled tube furnace. The reactor exhaust is directed to either a commercial Q Exactive Orbitrap Mass Spectrometer (m/z = 6000) for exact analysis of the reaction products via mass spectrometry (MS) or to a gas chromatograph to gain insights into the mechanism of the catalytic reactions. In addition to the initial investigations of the catalyst properties performed in Banerjee and Vaida laboratories, i.e. thickness, composition, and structure, the UGS will work in the UCF Materials Characterization Facility to record X-ray photoemission spectra (XPS) and transmission electron microscopy (TEM) images before and after chemical reactions. The XPS and TEM investigations will reveal changes in the oxidation state and morphology of the catalysts during the reaction, which will be correlated with changes in the catalyst efficiency. Consequently, this project will be able to provide detailed insights into the efficiency and stability of 2D nanostructured catalyst materials. The UGS involved in this project will learn important skills, such as operating a variety of analytical tools, flow controllers and flow reactors, including catalytic JSR. They will learn how to collect and evaluate data and apply kinetic concepts to quantify the efficiency and stability of catalytic materials.
Project 4. Topological quantum materials for potential energy-related applications (Dr. Madhab Neupane): Topological quantum materials (TQMs) comprise of a new class of exotic materials possessing symmetry- protected electronic quantum states which have high conductivity, long lifetime, and high mobility thus attracting enormous interest for application in energy conversion and storage, including water splitting, batteries, and supercapacitors. However, the main scientific challenge is to understand the mechanisms by which these topologically protected quantum states influence the chemistry and physics of the materials. This project addresses this fundamental question and uses the obtained results to search for new and better TQMs to address potential energy-related applications. The student working in this project will learn how to predict new TQMs with enhanced properties suitable for energy applications. The specific objectives for the student are: (i) to understand the mechanism of TQMs; (ii) to be able to perform rational synthesis of high-quality single crystals of new TQMs with potential functionalities employing the flux growth method in a box-muffle furnace; (iii) to characterize those materials using X-ray diffraction and energy- dispersive X-ray analysis to confirm their structure and chemical composition; (iv) to perform angle- resolved photoemission spectroscopy (ARPES) measurements that will reveal the signature of topologically protected states which can be helpful for tailoring the properties of TQMs. These measurements will be obtained using the laser-based ARPES system located in Neupane’s lab and (iv) fundamentals of data acquisition, analysis, and scientific paper writing.
Project 5. 2D nanostructured materials for energy applications (Dr. Mihai E. Vaida): The UGS will learn techniques for synthesis and characterization of two-dimensional (2D) semiconducting materials such as transition metal dichalcogenides (TMD) and 2D-2D as well as 2D-3D heterostructures. These materials are expected to be suitable for a wide range of cost-effective energy applications including as photocatalysts for conversion of synthetic gas to higher alcohols, photovoltaics, and optoelectronics. The scientific goal is to understand how the electronic properties of 2D-TMD are influenced by their thickness and heterostructure formed when combined with other 2D materials or with 3D single-crystal surfaces. The student working on this project will learn to synthesize 2D materials using PVD, acquire skills in using standard tools for surface characterization, gain a basic understanding in ultrafast spectroscopy, and learn material testing techniques in realistic conditions. Furthermore, the student will develop skills in data collection, analysis, and dissemination.
Project 6. Computational design of materials for energy (Dr. Talat S. Rahman): Computational design of novel materials for energy applications relies on accurate determination of their geometrical and electronic structure and functionalities which are best obtained through ab initio simulations based on density functional theory (DFT). A student with a background in quantum mechanics will have the opportunity to work on a project in which another REU student is carrying out experimental work in one of the projects mentioned above. Such a scenario would bring excellent synergy. The student workino on this project will learn the basics of DFT and the essential elements of electronic structure responsible for atomic scale bonding and system geometry. By calculating energetics of a variety of structures to determine their relative stability and the relationship between structure and property they will learn how DFT is used to rationalize experimental observations in related projects with an open eye for what it can explain and where it may fail. The student will seek answers to questions such as: what characteristics in the calculated electronic structure of the novel material lend themselves to energy applications?
Project 7: Transparent conducting thin-films (Dr. Parag Banerjee): This project focuses on understanding the physical and chemical nature of atomic layer deposition (ALD) processes that can be used to synthesize transparent conducting thin film electrodes for photovoltaic applications. By utilizing the “digital pulsing sequence” of ALD, compositional variation in thin films can be achieved with atomic-scale precision in a way that few other synthesis techniques can match. For example, doping of wide bandgap metal oxides such as ZnO has been shown to be a viable pathway for developing new highly efficient transparent conducting electrodes for use in solar cells [37-39]. Furthermore, in situ techniques that monitor ALD chemistry and film growth in real time leads to deeper understanding of the mechanistic aspects of film growth [40, 41]. There are primarily two in situ techniques that the Banerjee Lab exploits to understand ALD processes. The first involves the use of spectroscopic ellipsometry (SE) to monitor the physical film thickness and optical properties as a function of ALD process parameters. The second technique involves the use of quadrupole mass spectrometry (QMS). QMS identifies and monitors gaseous by-products of ALD reactions which help elucidate the chemistry of each half-reaction that leads to film growth. Taken together, SE and QMS provide a complete picture of the physical and chemical nature of an ALD process and the resultant film.
The scientific objective of this project is to understand the nature of co-dopants in ZnO films for transparent conducting applications. The driving hypothesis for this work is that there are multiple pairs of dopants which can be synergistically exploited to enhance the optical transparency and electronic conductivity in ZnO films. Most existing work on transparent conducting ZnO is related to single dopants such as, Ga3+, Al3+, Ti4+ and Ta5+. While some dopants exclusively improve crystallinity (e.g., Ga3+ improves electron mobility), others enhance carrier concentration (e.g., Al3+ improves electrons/cm3). It would be intriguing to exploit the combined effects by co-doping. This forms the basis of our hypothesis. The educational objective of this project is to expose students to the science and engineering of ALD as it pertains specifically to transparent conducting oxides. The learning objectives are to understand (i) the physical and chemical principles of ALD; (ii) the principles of SE and QMS and the role these techniques play in providing important real time information of ALD processes and; (iii) how ALD can be applied to design new transparent conducting oxides. At the end of the REU period, the student will have acquired the following skills: (i) the ability to conduct ALD processes on substrates such as glass and flexible poly- ethylene terephthalate (TEP) and; (ii) the ability to collate, analyze, interpret and corelate ALD process data such as pressure, temperature, flow rates, and ALD in situ data from SE and QMS.
Project 8: Characterization of photovoltaic materials (Dr. Paria Gharavi): An UGS will learn to characterize ZnO ALD-grown thin films from Project 7 using the cutting-edge facilities available at UCF. The project will focus on the atomic-scale structure of ZnO films, including grain-boundary structure and orientation, and elemental mapping of co-doped systems. Students will use electron microscopy, including SEM, TEM, and EDS. The UGS will work to map the distribution of dopants, which is likely to be relevant for microstructure and carrier mobility, both of which are relevant for photovoltaics. EDS along with TEM analysis will be used to characterize potential dopant segregation along GB regions. Microstructure characterization will be critical to both development of ALD growth and computational approaches to elucidate electronic and optical properties. Students who participate in this project will develop essential laboratory skills and experience in data analysis and the operation of electron microscopy. The student will interact with the other two studnets focusing on ALD of ZnO films (Project 7) and computational methods (Project 9).
Project 9: Tight-binding development and application to conducting thin films (Dr. Patrick Schelling): This project will be tightly integrated with the other two projects focused on transparent conducting films for photovoltaic applications. The project for the student will be based on DFT methods, and also the development of self-consistent tight-binding models. This approach has been developed by Schelling to describe materials properties of systems with physical dimensions beyond what is typically accessible to DFT calculations. Although DFT is used in the parameterization, the approach we propose is somewhat distinct from Density-Functional Tight-Binding (DFTB) which uses explicit basis functions. The advantage of our approach that separates it from standard tight-binding models is the addition of Coulomb self-consistency, which is essential for charged defects. The student in this project will interact with the student working on characterization (Project 8) to develop atomic-scale models of GB regions. The student will begin with small-scale DFT calculations of ZnO films, including energetics of dopants. Small-scale calculations of GB regions in films might be possible. However, one of the main objectives of DFT calculations will be to develop a database for parameterization of self-consistent tight-binding models. Traditional approaches to fitting the models will be explored, but beyond that. machine-learning (ML) techniques will also be explored. There have been a few reports of using ML for parameterization of models of this kind, but not with full Coulomb self-consistency. The student will elucidate tendency of defects to segregate in GB regions which will be related to electronic and optical properties.