Daniel R. Mumm - US grants

The objective of this research is to determine the feasibility of using a biological system for templating particles into well-ordered two- and three-dimensional assemblies, with the vision toward new applications in nanoscale optoelectronic devices and high temperature electrochemical systems. The approach is to attach inorganic nanoparticles to protein templates to form highly-ordered two-dimensional arrays, characterize the spatial and optical properties of these protein-nanoparticle assemblies, and use layer-by-layer assembly to build three-dimensional protein-nanoparticle hybrid materials.

Intellectual Merit:
This research will develop a new strategy to construct nanostructured materials. The ability to fabricate assemblies comprising small inorganic nanoparticles into arrays of predetermined spacing and arrangement is currently not feasible. By enabling lattice parameter manipulation and ordered layer-by-layer assembly, arrays that consist of particles exhibiting the quantum size effect may reveal new properties. This, in turn, could enable the design of novel devices in areas such as optoelectronic technologies and fuel cells.

Broader Impact:
The program is necessarily a multidisciplinary endeavor, and it therefore represents an excellent opportunity for students to participate in a collaborative team effort and be trained to work with team members of diverse backgrounds. Under this proposed project, students at all educational levels (graduate, undergraduate, and high school) will be actively recruited. The results of this proposed work will also be integrated into topics presented in graduate-level courses.

NON-TECHNICAL DESCRIPTION: Solid Oxide Fuel Cell (SOFC) technologies offer a means of minimizing emissions and increasing efficiency associated with electricity production from a variety of fossil fuels. The impact of successful development and commercialization of SOFC systems would fundamentally change future power generation. However, it remains a major challenge to develop electrochemical ceramic systems that offer high performance with long-term stability. SOFC systems are constructed of multiple materials in distinct layers. During operation, chemical and structural changes at the interfaces between these layers can lead to performance losses. This project uses coupled electrochemical measurements and microscopy/spectroscopy at the nanoscale to understand how different material interfaces evolve under SOFC operational conditions, such that more efficient and more durable material combinations can be designed. Over the course of this project, undergraduate students from the NSF California Alliance for Minority Participation (CAMP) program, an NSF REU program, and other undergraduate research programs will be involved in academic year and summer research activities (10-15 students during the project). In addition, high school teachers from three high-need southern California school districts will be engaged in summer research and curriculum development projects. The teacher-researcher program is a key factor in outreach to high school students, impacting ~150 students by the end of the project, introducing them to the materials science discipline and encouraging more students to enter into science and engineering careers that will address our nations future energy needs.
TECHNICAL DETAILS: The overarching objective is to develop an improved understanding of the interplay between mechanisms that govern performance in high-temperature electrochemical systems, and microstructural instabilities that lead to performance losses over time. The effort couples high-resolution imaging and microanalysis with traditional linear and emerging non-linear electrochemical test methodologies to better understand the links between the mixed ionic and electronic conduction (MIEC) characteristics of constituent materials, defect chemistry, microstructure, test/exposure conditions, and relevant electronic and ionic transport mechanisms. A primary focus is the systematic investigation of the electrochemical behavior of different classes of cathode materials that, despite spanning a wide range of relative electronic and ionic conductivities, show positive attributes as SOFC cathodes. Comparative testing of target materials sets, in symmetric and full cell test configurations, is used to discriminate between rate-controlling interfacial processes, thereby elucidating mechanisms that control the stability of key interfacial regions, and correlating these behaviors with the intrinsic electrode material properties using models of electrode mechanisms. Energy-filtered transmission electron microscopy and focused ion beam (FIB) techniques allow direct correlation of materials evolution (interface and surface chemistry and microstructure), electrochemical measurements, and intrinsic constituent material properties - at length scales relevant to the controlling mechanisms. Comparison of interfaces subjected to electric potential with regions that are disconnected from the electroded regions (using FIB techniques) is used to identify synergistic effects of electric fields, current density and exposure conditions on degradation processes. A mechanism-based model of these correlations is being developed to enable design of improved materials sets, and guide optimal development of a wide range of technologically important high temperature electrochemical devices. The graduate and undergraduate researchers will make fundamental contributions to the understanding of mixed conducting ceramics as electrochemical system electrodes, and be trained in cutting-edge research techniques critical to supporting future energy system development.

0966904
Law

This project will explore new ways to probe the surfaces of nanocrystalline solar cell materials and fuel cell electrodes using Fourier transform infrared (FTIR) spectrometry. The unique capabilities of this FTIR, including far-IR, in situ diffuse reflectance, and in situ variable-angle silicon and diamond attenuated total reflectance (ATR) spectroscopy will enhance efforts to develop fuel cell cathodes with much faster kinetics for oxygen reduction, as well as robust nanocrystal solids with long carrier diffusion lengths suitable for high-efficiency solar cells. The nanocrystal work will utilize applied studies of organic and inorganic ligand exchange, molecular bonding, surface diffusion, oxidation, doping and other surface processes occurring in electronically-coupled nanocrystal films. The fuel cell work will leverage the instrument's unique in situ capabilities to explore the polarization processes of solid oxide cathodes under operating conditions.

Intellectual Merit

The use of FTIR to probe the surfaces of nanocrystalline solar cell materials and fuel cell electrodes will answer important questions concerning the surface composition and interfacial dynamics of these materials. For example, colloidal nanocrystal solids are a novel class of hybrid organic/inorganic materials with great technological potential in optoelectronics, but little is known about how the electronic properties of these materials depend on the atomic and molecular species that are adsorbed on their large internal surface. FTIR will help to elucidate the structure-property relationships needed to develop nanocrystal-based devices, particularly cheap and efficient solar cells for large-scale power conversion.

Broader Impacts

This project will fund the acquisition of a PerkinElmer Spectrum 400 Fourier transform infrared (FTIR) spectrometer to support ongoing and future research projects in the areas of nanostructured solar cells and fuel cells by two assistant professors in the Physical Sciences and Engineering at UC Irvine.

In addition to opening new avenues for research in alternative energy and other areas, acquisition of the proposed instrument will greatly enhance teaching and training capabilities at UCI. The instrument will be used by postdocs, graduate students and undergraduate researchers to address vital questions in their research. No fewer than 16 Chemistry and Materials Science and Engineering students will utilize the instrument in the first two years. At least one hundred students will benefit from employing advanced FTIR techniques in their research over the lifetime of the instrument. The FTIR will be used in summer research programs for local high school students run by the Center for Solar Energy, in which students pursue projects in several chemistry and materials science labs over the course of the summer and present posters about their research at the Orange County Science Fair, as well as the California State Summer School for Mathematics and Science (COSMOS-UCI), a month-long summer session funded in part by the National Science Foundation. The instrument will also be used by at least one minority undergraduate researcher every year as part of the California Alliance for Minority Participation (CAMP) Summer Scholars Program.

With this award from the Chemistry Major Research Instrumentation (MRI) Program and co-funding from the Chemistry Research and Facilities (CRIF) Program, Professor John Hemminger from University of California Irvine and colleagues Regina Ragan, Matthew Law, Reginald Penner and Daniel Munn will acquire a combined X-ray photoelectron spectrometer (XPS) and scanning Auger microprobe (SAM). The proposal is aimed at enhancing research and education at all levels, especially in areas such as (a) XPS and Auger electron spectroscopy (AES) depth profiling, SAM, and UPS studies of solar cell absorbers and device stacks; (b) characterization of metal oxide and metal chalcogenide nanocrystals for photocatalysis; (c) ultraviolet photoelectron spectroscopy (UPS), XPS and AES depth profiling studies; (d) manganese dioxide nanowires for ultra-high capacity and rate capabilities for lithium cathodes; (e) correlating surface functionalization and transport properties of single-walled carbon nanotubes; and (f) dynamics of thermally-grown oxides in power generation and propulsion materials.

X-ray photoelectron spectrometers are used for chemical analysis. The XPS technique quantitatively measures elemental composition, empirical formula, chemical state and electronic state of the elements in a given material. A sample is irradiated with a beam of monochromatic X-rays and the kinetic energies of the resulting photoelectrons are measured and related to specific elements. XPS often plays a crucial role in defining the system under study. The technique requires the use of ultra-high vacuum conditions. In Auger electron spectroscopy, energetic electrons emitted from an excited atom are analyzed to provide information on surfaces. The work to be carried out by these investigators represents a wide array of systems requiring surface characterization. The instrumentation will be used in research activities and also for research training and education of a large number of students from diverse backgrounds.