Hybrid Nanostructured Organic-Inorganic Catalysts for Water Electrolysis

Hydrogen is a promising energy carrier, but also a valuable chemical used in a variety of industrial processes. Hydrogen is typically produced from natural gas by steam reforming, a process which requires high temperatures and generates CO2. More sustainable routes for H2 production exist. Water electrolysis, for example, is carried out at room temperature, H2 and O2 are the sole products of the reaction, and photovoltaics or wind turbines can supply the current. Unfortunately, several challenges remain.

The Long and the Short of It: Nanostructure of Thermoelectric Materials

Highlight Date: 
08/07/2013
Display Section: 
Broad Audience Highlights
Article Title: 
Analysis of Phase Separation in High Performance PbTe–PbS Thermoelectric Materials
Author(s): 
S. N. Girard, K. Schmidt-Rohr, T. C. Chasapis, E. Hatzikraniotis, B. Njegic, E. M. Levin, A. Rawal, K. M. Paraskevopoulos, and M. G. Kanatzidis
Article Link: 
Journal Name: 
Advanced Functional Materials
Volume: 
23
Year: 
2013
Page Number(s): 
747-757
Project Affiliation: 
Highlight Text: 

A study of thermoelectrics, materials that convert heat to electricity, demonstrates the importance of characterizing materials using several different methods. According to Vegard’s Law of Alloys, the size of a crystalline lattice (lattice parameter) changes linearly with composition. It is actually not a law, but an empirical observation that has been found to hold true for a majority of alloys. Researchers studied thermoelectrics made from lead, tellurium, and sulfur and varied the tellurium and sulfur content to answer the question “If a thermoelectric follows Vegard’s Law, does that make it an alloy?” The answer is: not necessarily.  High-resolution synchrotron X-ray diffraction data taken at the Department of Energy’s Advanced Photon Source, probing long-range order, shows that this material adheres to Vegard’s Law. Solid-state tellurium (125Te) nuclear magnetic resonance (similar to magnetic resonance imaging) was used to determine the short-range structure and composition of the samples with high accuracy; sulfur shows strong effects on the resulting NMR spectra, with the Te peaks shifted depending on the number and arrangement of sulfur atoms near Te.  Combined NMR and infrared spectroscopy results show that above 16% sulfur the samples are not alloys. Additionally, inhomogeneities improve the material’s ability to convert heat to electricity.  These findings suggest that there may be many thermoelectric systems that are not alloys as reported, but instead are nanostructured.  The work also demonstrates the importance of using probes of both long range and local chemical structure to differentiate between alloys and composites.

Predicting Unusual Deformation Behavior in Materials

Highlight Date: 
08/06/2013
Display Section: 
Broad Audience Highlights
Article Title: 
Stability Maps to Predict Anomalous Ductility in B2 Materials
Author(s): 
R. Sun and D. D. Johnson
Article Link: 
Journal Name: 
Physical Review B
Volume: 
87
Year: 
2013
Page Number(s): 
104107
Project Affiliation: 
Highlight Text: 

For the first time, researchers can now both explain and predict the behavior of different materials while they are being pulled apart.  Some materials are ductile, meaning they will deform without losing their toughness, and others are brittle.  The results explain even the unexpected ductility of a material within a class of rare-earth-containing materials that are otherwise known to be brittle.  To predict the behavior requires two maps.  The first map reveals whether a system has the ability to slip in a particular direction and form stable defects (a necessary condition for ductility), while the second map reveals if the required defects have multiple, active slip planes (a sufficient condition).  With both conditions satisfied, the material will be exhibit unusual ductility. The maps are accurate, with observed ductile to brittle transitions reproduced, too.  Similarly criteria can be formulated for a variety of systems — a direct form of computational materials discovery.

 

Modeling Organic Semiconductor Light Emitting Devices (OLEDs)

The goal of the SULI project will be to model organic semiconductor light emitting devices (OLEDs) that are being fabricated within the Photonic Systems FWP. We will develop a novel Monte-Carlo approach to model the transport of holes and electrons in these devices, together with their recombination, that results in the emission of light. Experimentally determined mobilities of electrons and holes and electronic energy levels will be utilized.

Mass Spectrometry Uses in Alternative Energy

Mass spectrometry determines the molecular weight of ionized molecules, from small metabolites to large biological compounds like proteins.  New refinements to this technique also allow measurement of the three-dimensional structure of the ions using a method called ion mobility spectrometry.  We have new instrumentation that combines laser desorption ionization and/or electrospray ionization with ion mobility and time-of-flight mass spectrometry to provide even more thorough measurements of the actual structures of the ions.  This instrumentation is being used to monitor met

Heterogeneous catalysts for renewable energy

SULI 1: Precious metals and metal alloys are important heterogeneous catalysts for renewable energy and materials. However, both of them have their limitations. Precious metals have low natural abundance and are expensive. Metal alloys have unstable surfaces due to surface segregation under reaction conditions, which renders the identification of active sites and the understanding of reaction mechanisms difficult. My research group will address these limitations by developing new intermetallic NP catalysts.

Quantum control of magnetism

We seek motivated undergraduates in our lab to address an outstanding and cross-cutting challenge of condensed matter/chemical/biological physics: how to achieve quantum control of magnetism and reveal highly non-equilibrium, “thermodynamically hidden” orders during femtosecond timescales? One example is a new paradigm discovered by our group called quantum femtosecond magnetism—fs magnetic and electronic phase transitions driven by quantum spin flucations and laser-excited inter-atomic coherences (T. Li, et al., Nature, 496, 69, 2013).

Nanostructured materials

"We develop high surface nanostructured materials, functionalized with multiple organic and inorganic groups to make smart multitasking nanoparticles. We employ these nanomaterials to various fields such as catalysis, CO2 capture and conversion, environmental remediation as well as biomedical research and biotechnology.