2018 Eilers Scholars
Catalytic performance of molybdenum based bimetallicphosphide catalysts for C-O bond activation for renewable energy production
Department of Chemical and Biomolecular Engineering
Faculty Advisor: Jason C. Hicks
Due to the increase in the global energy demand and the decrease in global petroleum sources, renewable energy alternatives must be explored. One of the most attractive sources of renewable energy is carbon-rich, lignocellulosic biomass found in non-food crops, plants and trees due to their natural abundance. The three components of lignocellulosic biomass are cellulose, hemicellulose, and lignin. In our work, we focus on upgrading the hemicellulose and lignin derivatives as cellulose is highly utilized in the pulping process to make paper. Lignin provides a sufficient energy source due to its rich aromatic and aliphatic content. One of the major challenges, however, is that lignin has a 10-30% oxygen content, which lowers its heating value and decreases its utility as a fuel. To counteract this issue, oxygen needs to be removed via cleavage of both C-O aliphatic bonds and C-O aromatic bonds to remove the unwanted oxygenated functionalities. A thermochemical method (i.e. pyrolysis and liquefaction) is usually employed to produce bio-oil from solid lignocellulosic biomass, cleaving the C-O aliphatic bonds. Nevertheless, the resulting mixtures remain highly oxygenated and include species such as phenolics. The C-O aromatic bonds in phenolics have high bond breaking energy (~469 kJ/mol) that is almost equivalent to the bond breaking energy of strong C-H aromatics (~481 kJ/mol). In order to deoxygenate the phenolics further, we need a catalyst that can selectively rupture the C-O aromatic bonds through a hydrodeoxygenation reaction (HDO) while maintaining the aromaticity of the phenolics to achieve high hydrogen efficiency in the process. Meanwhile, the hemicellulose part of lignin is often upgraded into furfural that is then processed further into other chemicals. However, furfural upgrading often results in ten different products due to side reactions. Therefore, a selective catalyst that could eliminate side reactions is needed. A class of materials that the Hicks group has shown to be active for C-O bond cleavage reactions is transition metal phosphides. These materials are hard like ceramics and have high thermal stabilities. The emphasis of my work has been on investigating the enhancement if catalytic activity, selectivity and stability of bimetallic phosphides catalysts due to the incorporation of two metals in the resulting solid solution. Specifically, my research project is focused on studying the relationship between surface properties and the bulk, structural properties and how these dictate their catalytic performance. In my recent work, I have found that there is a strong correlation between the relative oxidation of the metals and the product selectivity in hydrodeoxygenation reactions. I have also discovered that some of the bimetallic phosphides are active at low temperatures, which opens up a wide operating window of these materials to upgrade biomass near ambient conditions.
Elucidating the Role of Electrostatic Interactions in Facilitating Ion Transport through Charge-Mosaic Membranes for Water Purification and Desalination Applications
Department of Chemical and Biomolecular Engineering
Faculty Advisor: William A. Phillip
Charge-mosaics, which consist of patterned micro-/nano-scale domains of opposite charge on a single membrane, are capable of transporting ionic solutes more rapidly than neutral particles of comparable or larger sizes. We hypothesize that this unique capability is closely related to the electrostatic interactions between the fixed charge on the membrane surface and the charged solutes permeating through the membrane. Therefore, the proposed study will focus on developing the fundamental knowledge that enables the design and fabrication of high-performance charge-mosaic membranes that can selectively remove salts from aqueous solution by examining these electrostatic interactions in detail. This knowledge will be developed by using our ability to pattern the membrane surface chemistry using inkjet printing devices in order to tailor the membrane surface properties systematically and characterize the corresponding effects on the separation performance. The charge-mosaic membranes present several operational advantages in separation processes where the target solutes are dilute in concentrations (e.g., nutrient recovery from wastewater, recovery of lithium from expired batteries). Therefore, the development of high-performance charge-mosaics through the proposed fundamental studies offers a pathway toward more energy-efficient chemical separations.
Charge Carrier Migration and Halide Ion Movement in All-Inorganic Perovskite Films for Photovoltaic Applications
Department of Chemistry and Biochemistry
Faculty Advisor: Prashant V. Kamat
Perovskite solar cells have achieved record efficiencies of 22.1% making them a promising material to be used in future photovoltaic devices. Their tunable band gap over the entire visible region, solution processing fabrication that is easily scalable, and low temperature manufacturing make perovskite solar cells a promising material to be used in the next generation of solar cells. However, issues still remain with regards to stability. One major stability issue occurs in mixed halide perovskites, the type that have been used to create the most efficient cells, during irradiation. When segregation of highly mobile halide ions in mixed halide perovskites occurs under irradiation, the creation of trap state recombination due to this segregation causes a loss of efficiency.
Studying the movement of these halide ions would provide valuable information about the composition of these materials. By characterizing the movement of these halide ions, steps can be taken to inhibit the segregation and therefore improve the efficiency and stability of these materials. Gradient halide perovskites, which have been reported in previous literature, provide a unique material that can be homogenized and analyzed to study the migration of the halide ions through perovskite films. By creating cesium lead bromide films and then creating a gradient halide perovskite film through an iodide exchange process, I propose to investigate the charge carrier migration and movement of halide ions in cesium lead halide perovskite structures and establish strategies to stabilize mixed halide perovskites with greater photo-conversion efficiency in photovoltaic devices.
Urea electrolysis cells for producing hydrogen fuel
Department of Civil and Environmental Engineering and Earth Sciences
Faculty Advisor: Kyle Doudrick
As global climate change, global population rise, and natural resource constraints continue to impact the planet, development of new, environmentally sustainable energy technologies is a primary concern. This project will explore an emerging approach for hydrogen fuel generation as a product of electrochemical oxidation (electrooxidation) of urea using electrolysis. The project involves the use of nanostructured nickel-based anodes in urine electrolysis cells to achieve various energy related impacts such as improving energy efficiency of wastewater processing, promoting the circular energy economy, diversifying energy production options, and reducing the environmental impact of various nonrenewable fuel sources. The project will specifically investigate the physicochemical mechanisms between urine components and inorganic nickel catalysts, and how they impact the hydrogen production efficiency of urine electrochemical cells. A synthetic urine recipe published in previous reports will be employed throughout this study. This technology seeks to turn a waste stream and turn it into a fuel source based on the knowledge from thermodynamics less energy is required to extract hydrogen from organic compounds such as urea than from water splitting for hydrogen generation.
Currently, many researchers have investigated the interaction of nickel catalysts of various forms with urea but the effects of the different components such as phosphate, sulfate, gelatin, and nutrient broth present in a realistic urine medium have not been thoroughly investigated. A nickel synthesis process that produces nickel nanostructures on carbon paper electrodes for future adaptability in a membrane electrode assembly electrolysis cell for efficient electrode spacing and reactor design has been developed for this project. The reactor design and experimental procedures have been identified and optimized to complete the study. The materials will be characterized using advanced physical and chemical characterization techniques before and after electrochemical experimentation including scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (XRD), and Xray photoelectron spectroscopy (XPS) to understand not only the interaction between the nickel catalyst and urea but how the other urine components effect the catalyst/urea interaction. Various electrochemical metrics relating to applied voltage and current output will reveal the limitations presently restricting this technology from implementation. The electrolysis experiments will be carried out using various electrochemical techniques such as linear sweep voltammetry and cyclic voltammetry to understand the redox mechanisms, and then chronoamperometry will be used to evaluate component effects on catalyst stability and reaction kinetics. These results will further the understanding and outlook for using real urine in electrochemical systems as a means for producing hydrogen fuel from a waste stream.