Chemical Dynamics and Diagnostics
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Current Areas of Research
Low-Pt electrocatalysts for PEM fuel cell cathodes
Oxide- and phosphate-based electrocatalysts are being developed as low-cost, high-durability alternatives to the state-of-the-art carbon-supported Pt clusters for the oxygen reduction reaction (ORR) at the cathodes of proton exchange membrane (PEM) fuel cells. The activities of the catalysts are characterized with rotating disk electrode (RDE) and rotating ring disk electrode (RRDE) voltammetry, and spectroscopies including X-ray photoelectron spectroscopy and X-ray absorption spectroscopy. The catalysts are also cast into membrane electrode assemblies (MEAs) and tested as fuel cells.
Sulfur-tolerant catalysts for fuel cells
Conventional PEM fuel cell catalysts are susceptible to poisoning from ppb of sulfur in the air and fuel stream. We are developing electrochemical methods to study the electrocatalytic mechanisms of sulfur poisoning on conventional platinum catalysts using them to make poisoned catalysts withstand naval environments. The mechanisms of sulfur-poisoning are studied on the conventional platinum catalysts for PEM fuel cells using as RDE and RRDE voltammetry and also in fuel cell membrane electrode assemblies. The phosphate and oxide catalysts above are studied for their SO2 tolerance in air. We also study alternative membranes. X-ray absorption spectroscopy is used for additional chemical insights.
NRL is developing a new fuel cell powered unmanned air vehicle capable of 24hr missions for persistent surveillance and sensing. This work is in collaboration with NRL Code 5712.
Battery materials development
New cathode and anode materials for Li-ion batteries are being developed with the help of first principles theory (density functional theory) in collaboration with NRL Code 6930. The theory is used to predict materials properties, and the materials are synthesized in the lab and demonstrated in small batteries.
Micro microbial fuel cell
We are developing miniature power sources that harvest energy from the natural environment through microbial metabolism of indigenous nutrients. These miniature microbial fuel cells have demonstrated high power per cross-sectional area and device volume under both anaerobic and aerobic conditions. Further work is focused on creating long-endurance biofilms of specialized bacteria through novel electrode treatments. The end goal of the program is to develop versatile, long-lasting power sources that can be used in various underwater applications including sensor nodes and unmanned underwater vehicles.
Biological Laser Direct Write
We are investigating novel additive methods to directly deposit micro- and nano-patterns of biological and inorganic materials onto relevant substrates and devices. Experiments utilizing biological printing involve the formation of microarrays and microstructures of living cells or active biomolecules for both sensing and tissue engineering applications.
Nanoscale Biological Electron Transfer
We are investigating how metal reducing bacteria interact with their environment on the nanoscale. These microorganisms are capable of performing both direct (membrane and/or nanowire assisted) and indirect (mediated via redox active molecules) extracellular electron transfer to soluble and insoluble electron acceptors. When a biofilm of these microorganisms is maintained on an electrode, current and power can be harvested from their metabolism, making these studies potentially relevant for powering underwater autonomous systems or nanoscale electronics. A range of nano-analytical equipment is used to image nano-filaments (scanning electron microscopy (SEM), environmental SEM, atomic force microscopy (AFM), transmission electron microscopy (TEM)), and characterize their electron transfer (nanoprobe, conducting AFM, nanoelectrode arrays).
Waste to Fuels
The objective of this program is to increase primary paraffin aviation fuel components (linear and branched alkanes with carbon lengths between C8-C18) and lubricants from naval waste (food, feces, greywater) using microbial pre-treatment in addition to a rapid and efficient electric pyrolysis procedure. The success of this project will ultimately result in a method to reduce 70% of the bulk aqueous and solid waste volume stored and transported for disposal from both ship and land-based installation, while yielding a 15% increase in paraffin JP-5 fuel components and lubricants generated on-site.
Development of Selective Carbon Monoxide (CO) Preferential Oxidation Catalysts
Our primary objective is to develop novel room temperature, selective halogenated organometallic metal complexes for gases in typical reformate gas mixtures (CO, CO2, N2, H2, H2O(gas)). These catalysts will ultimately be used to scrub or harvest CO from complex reformates, leading to the direct conversion of CO into electricity. These catalysts and their eventual integration into their own fuel cell/scrubbing system will increase the efficiency, selectivity, sustainability and power output from the reforming process by: 1) increasing the selectivity for carbon monoxide in the presence of hydrogen at room temperature by decreasing the electron density on the catalytic metal center, 2) generate electricity from the reaction of carbon monoxide with the conducting polymer catalyst by immobilization on conductive carbon supports, and 3) purify hydrogen fuel streams from sources as impure as biomass to methane at room temperature.