Nanostructured Hybrid Composite Membranes for Fuel Cells

Fuel cells have been identified as one solution for reducing dependence on foreign oil and lessening the environmental impact of burning fossil fuels. One type of fuel cell, the PEMFC (polymer electrolyte membrane or proton exchange membrane) operates typically below 100 oC and utilizes H2, either directly or via a reformate, or methanol as a fuel source. One problem revolves about the chemical intermediates or impurities, especially CO, that poisons the catalyst, thus reducing fuel cell life and efficiency. The effects of these intermediates is lessened by running the fuel cell at higher temperatures (120-150 oC) but this causes dehydration in the current PEM materials, unless the cell is pressurized, which adds to the cost. Enhanced FC efficiency and operation would be realized from the development of membrane materials that can operate at elevated temperatures without being dehydrated. Hybrid nanostructured organic/inorganic composite membranes represent a novel approach to minimizing humidification requirements.

Carbon Nanotube Fiber Supercapacitors

Supercapacitors based on CNTs are electrochemical energy storage devices that can ultimately deliver capacitances as high as 300 F/gm. Recent advances at UTD in the fabrication of CNT fibers have enabled us to incorporate them into a number of novel supercapacitor configurations. The combination of superb energy storage, high electrical conductivity and spectacular mechanical properties of these fibers affords unprecedented application opportunities. In their simplest embodiment, two electrolyte-coated fibers are twisted together to produce a yarn that has been woven into a multifunctional electronic textile. Winding the devices around a form provides the basis for energy-storing structural composites.

Carbon Nanotube Electrode Assemblies for Thermal Energy Harvesting

Thermoelectrochemical cells are devices that convert thermal to electrical energy based on the temperature dependence of electrochemical redox potentials. Using specially constructed carbon nanotube electrodes we have recently demonstrated power densities of >11 W/kg for a 70 oC temperature difference. The high power generation capability of the carbon nanotube electrodes apparently results from the high electrochemically accessible surface area, and the high density-of-states at the Fermi level. Since our power generation is proportional to T 2, we may be able to increase electrical power density of the carbon nanotube electrode to 155 W/kg by increasing T to 300 oC. Our future work focuses on finding higher thermal stability electrolytes, optimizing nanostructured electrode materials, and making all-solid-state thermal energy harvesting cells.

Nanoscale Polymeric Photocells by Advanced Electrospinning

The goal of this research is to create by advanced electrospinning synthetic methods, the prototypes of fully organic and organic/inorganic composite, deployable photocells. These photocells, comprised of donor and acceptor conjugated polymeric nanofibers or nanoporous semiconductors (as the photoactive part) combined with carbon nanotubes (as nanoscale charge collectors) and engineered at nanoscale dimensions, will maximize the efficiency of light transformation into charged layers to generate electric power.

Thermal Conductivity Enhancement by Optical Phonon Sub-Band Engineering of Nanostructures

Our research goal here is to use experimental and theoretical approaches to develop a deep understanding of the physics of phonons in nanostructures, and to use this understanding for demonstrating systematic methods for obtaining materials having very high phononic thermal conductivities (Kph). One of the approaches we are taking involves the synthesis of both carbon and BN nanotubes within the pores of zeolites.

The Rational Design and Synthesis of Carbon Nanotubes of One Specified Type

The absence of a route for producing identical carbon nanotubes has seriously limited both fundamental investigations and applications since macroscopic measurements typically provide a weighted average of the properties of metallic and semiconducting nanotubes. To avoid this averaging, nanoprobe methods are used for characterizing the structure and properties of individual nanotubes, but these methods are both tedious and totally unsuitable for commercial application. For example, nanotube transistors are typically made by assembling nanotubes of unknown structure, and testing to see if the randomly selected metallic or semiconducting nanotubes provide the desired device function. The availability of synthetic routes to specific targeted nanotubes would eliminate these problems, and enable the synthesis of nanotube fibers and sheets having optimized properties for thermal energy harvesting, conversion, storage, and transmission, as well as electronic devices.

Carbon Nanotube Artificial Muscles

Conversion of electrical energy to mechanical energy in carbon nanotube artificial muscles is another focus, which can be game changing for applications as diverse as medical devices for minimally invasive surgery to clothing that adjusts porosity in response to changes in temperature or activity levels or in response to chemical or biological threats. We invented carbon nanotube artificial muscles and demonstrated that these muscles provide a hundred times the force generation capability of natural muscles and twice the rate capability.

Spinning Carbon Nanotube Composite Fibers

The use of carbon nanotubes for many NanoEnergetic applications depends upon their availability as fibers having exceptional properties. We have spun carbon nanotube composite fibers at a hundred times the prior-art rate, and obtained fibers that pound-per-pound have twice the strength and stiffness and 70 times the toughness of strong steel wire. In addition to other functionalities, we have used these fibers for both electrical energy transmission and sensor devices in electronic textiles.

Highly Energy Efficient, Low Voltage Organic Light Emitting Devices (OLEDs)

Lighting devices presently in use have very low power efficiencies. Our Institute is working on a new concept of increasing the efficiency of OLEDs, which uses nanostructured layers doped by organic molecules, which are strong donors and strong acceptors. This combination will allow us to increase the injection of carriers at lower voltages and increase their conductivity. Research on novel types of devices with hybrid organic/inorganic layers is a major activity of the NanoTech Institute in general, for which we are creating a unique fabrication facility incorporating both vacuum deposition and PVD chambers attached in a modular array.

Carbon Nanotube/Biological Molecule Composites

Designer proteins and polynucleotides are being constructed and their interactions with nanotubes and other nanostructures are being investigated for various applications including sensors and drugs.