A5003787811- Electrocatalysts for Energy Conversion
- Fuel Cells and Related Materials
- Advanced battery technologies research
- Electrochemical Analysis and Applications
- CO2 Reduction Techniques and Catalysts
- Advancements in Solid Oxide Fuel Cells
- Conducting polymers and applications
- Catalytic Processes in Materials Science
- Electron and X-Ray Spectroscopy Techniques
- Ionic liquids properties and applications
- Advanced Materials Characterization Techniques
- Machine Learning in Materials Science
- Semiconductor materials and devices
- Advanced Battery Materials and Technologies
- Hybrid Renewable Energy Systems
- Catalysis and Hydrodesulfurization Studies
- Nanoporous metals and alloys
- Analytical Chemistry and Sensors
- Advanced Memory and Neural Computing
- Advanced Battery Technologies Research
- Catalysis and Oxidation Reactions
- Membrane-based Ion Separation Techniques
- Green IT and Sustainability
- Metal and Thin Film Mechanics
- Electrospun Nanofibers in Biomedical Applications
National Renewable Energy Laboratory
2016-2025
Oak Ridge National Laboratory
2023
University of Houston
2008-2010
General Motors (United States)
2005-2009
DEVCOM Army Research Laboratory
2007
University of Rochester
2005-2007
General Motors (Poland)
2006
Insufficient catalytic activity and durability are key barriers to the commercial deployment of low temperature polymer electrolyte membrane (PEM) direct-methanol fuel cells (DMFCs). Recent observations suggest that carbon-based catalyst support materials can be systematically doped with nitrogen create strong, beneficial catalyst-support interactions which substantially enhance stability. Data functional groups introduced into a carbon appear influence at least three aspects...
Limiting current measurements in a polymer electrolyte membrane (PEM) fuel cell are used to separate the oxygen-transport resistance into individual component parts. By varying thicknesses of diffusion medium (DM) and microporous layer different builds, total transport is separated contributions from flow channels, DM, layer, all other sources. pressure, pressure-dependent (intermolecular gas diffusion) pressure-independent (Knudsen or through ionomer/liquid water layers). In addition oxygen...
The exchange current density for the hydrogen oxidation/evolution reactions was determined in a proton membrane fuel cell. Ultralow Pt-loaded electrodes were used to obtain measurable kinetic overpotential signals ( at ). Using simple Butler–Volmer equation, and transfer coefficient lie within range of 0.5–1, respectively. Due fast kinetics, no voltage losses are predicted pure- cell applications when lowering anode Pt loadings from its value automotive target .
The oxygen reduction reaction (ORR) kinetics of a high-surface-area carbon-supported platinum catalyst were measured in an operating proton exchange membrane fuel cell (PEMFC). ORR can be described over wide range temperature, pressure, and current density using four catalyst-specific parameters: transfer coefficient, density, order with respect to partial activation energy. These parameters extracted combined kinetic thermodynamic model, either referenced the reversible potential (i.e., as...
Unsupported iridium (Ir) nanoparticles, that serve as standard oxygen evolution reaction (OER) catalysts in acidic electrolyzers, were investigated for electrochemical performance and durability rotating disk electrode (RDE) half-cells. Fixed potential holds cycling applied to probe the of Ir losses found be driven by particle growth (coarsening) at moderate (1.4 1.6 V) dissolution higher (≥1.8 V). Several different commercially available samples evaluated standardized conditions comparison...
This work demonstrated a robust, scalable cell architecture for electroreduction of CO2 (CO2R). An up to 90% faradaic efficiency the conversion CO2R formate at 500 mA/cm2 was realized 25 cm2 gas diffusion electrode (GDE) with carbon-supported SnO2 electrocatalyst. A 1.27 mm thick catholyte used between bipolar membrane and cathode GDE, which could be further reduced tens micrometers upon refinement. The deconvolution potential drop from each individual component/process guides pathways...
This work presents a study of the effects ultrasonic dispersing methodology and time on catalyst agglomerate size in polymer electrolyte membrane fuel cell (PEMFC) ink dispersions. Cathode inks were prepared characterized to elucidate influences method particle CCL electrochemical properties. In-situ ultra-small-, small-, wide-angle X-ray scattering (USAXS–SAXS–WAXS) analyses used impact ultrasonication changes agglomerate, aggregate, distribution during process. Ex-situ transmission...
The following model/experiment comparisons aid in predicting the maximum performance of a proton exchange membrane fuel cell (PEMFC) for cathode catalyst with known oxygen reduction reaction (ORR) kinetics absence gas transport resistances. Specific focus was on modeling voltage loss within layer, which results from balance between slow ORR and resistance to transport. A unique plot correction vs ratio ohmic (expressed by conduction sheet resistance, ) charge transfer Tafel slope over...
The theoretical contributions to overall cell voltage in a proton exchange membrane fuel (PEMFC) were calculated, accounted for, and compared measured IR free as relative humidity was varied from 30-110%. intrinsic oxygen reduction reaction (ORR) kinetics PEMFC, with regards water activity, shown be independent of above 50-60%, but significant losses ORR observed at lower values. amounted ca. 20 mV , corresponding an approximate two-fold decrease the current density. dependence on activity...
We have explored bimetallic Ru–M oxygen evolution reaction (OER) electrocatalysts for use in water splitting acidic electrolytes. Using an electrochemical multielectrode cell, we investigated the OER activity of selected compositions seven binary alloy systems, . Benchmarked using pure Ru electrocatalysts, Ru–Co, Ru–Ir, and Ru–Cu exhibited improved mass-based catalytic activities. Structural studies precursor alloys indicated presence hexagonal cubic mixed metal phases. hypothesize that...
To increase the commercialization of fuel cell electric vehicles, it is imperative to improve activity and performance electrocatalysts through combined efforts focused on material characterization device-level integration. Obtaining fundamental insights into ongoing structural compositional changes crucial for not only transitioning an electrode from its as-prepared functional state, also known as "conditioning", but establishing intrinsic electrochemical performances. Here, we investigated...
We present a rheological investigation of fuel cell catalyst inks. The effects ink parameters, which include carbon black-support structure, Pt presence on support (Pt–carbon), and ionomer (Nafion) concentration, the microstructure inks were studied using rheometry in combination with ultrasmall-angle X-ray scattering (USAXS) dynamic light (DLS). Dispersions high-surface-area (HSC), or Ketjen black type, demonstrated higher viscosity than Vulcan XC-72 due to both internal porosity more...
In situ electrochemical diagnostics designed to probe ionomer interactions with platinum and carbon were applied relate coverage conformation, gleaned from anion adsorption data, O2 transport resistance for low-loaded (0.05 mgPt cm–2) platinum-supported Vulcan (Pt/Vu)-based electrodes in a polymer electrolyte fuel cell. Coupling the diagnostic data ex characterization of catalyst inks electrode structures, effect ink composition is explained by both ink-level that dictate microstructure...
Results of a 2-D transport model for gas diffusion electrode performing CO2 reduction to CO with flowing catholyte are presented, including the concentration gradients along flow cell, spatial distribution current density and local pH in catalyst layer. The predicts that both buffer electrolyte gradually diminish channels parallel as result electrochemical conversion nonelectrochemical consumption. At high single-pass conversions, significant exist leading large variations (>150 mA/cm2),...