Matching Items (8)

Nanocatalysts for Low Temperature Fuel Cells

Description

Zeolitic Imidazolate Frameworks (ZIFs) are one of the potential candidates as highly conducting networks with surface area with a possibility to be used as catalyst support. In the present study,

Zeolitic Imidazolate Frameworks (ZIFs) are one of the potential candidates as highly conducting networks with surface area with a possibility to be used as catalyst support. In the present study, highly active state-of-the-art Pt-NCNTFs catalyst was synthesized by pyrolyzing ZIF-67 along with Pt precursor under flowing Ar-H[subscript 2] (90-10 %) gas at 700 °C. XRD analysis indicated the formation of Pt-Co alloy on the surface of the nanostructured catalyst support. The high resolution TEM examination showed the particle size range of 7 to 10 nm. Proton exchange membrane fuel cell performance was evaluated by fabricating membrane electrode assemblies using Nafion-212 electrolyte using H[subscript 2]/O[subscript 2] gases (100 % RH) at various temperatures. The peak power density of 630 mW.cm[superscript 2] was obtained with Pt-NCNTFs cathode catalyst and commercial Pt/C anode catalyst at 70 °C at ambient pressure.

Contributors

Created

Date Created
  • 2017-11-16

128228-Thumbnail Image.png

Nanomaterials for Energy and Environmental Applications

Description

Nanomaterials enabled technologies have been seamlessly integrated into applications such as aviation and space, chemical industry, optics, solar hydrogen, fuel cell, batteries, sensors, power generation, aeronautic industry, building/construction industry, automotive

Nanomaterials enabled technologies have been seamlessly integrated into applications such as aviation and space, chemical industry, optics, solar hydrogen, fuel cell, batteries, sensors, power generation, aeronautic industry, building/construction industry, automotive engineering, consumer electronics, thermoelectric devices, pharmaceuticals, and cosmetic industry. Clean energy and environmental applications often demand the development of novel nanomaterials that can provide shortest reaction pathways for the enhancement of reaction kinetics. Understanding the physicochemical, structural, microstructural, surface, and interface properties of nanomaterials is vital for achieving the required efficiency, cycle life, and sustainability in various technological applications. Nanomaterials with specific size and shape such as nanotubes, nanofibers
anowires, nanocones, nanocomposites, nanorods, nanoislands, nanoparticles, nanospheres, and nanoshells to provide unique properties can be synthesized by tuning the process conditions.

Contributors

Created

Date Created
  • 2015-11-23

128007-Thumbnail Image.png

Modeling and Simulation of Biologically Inspired Flow Field Designs for Proton Exchange Membrane Fuel Cells

Description

Various biologically inspired flow field designs of the gas distributor (interconnector) have been designed and simulated. Their performance using Nafion-212 with humidified H[subscript 2] and Air at 80 °C with

Various biologically inspired flow field designs of the gas distributor (interconnector) have been designed and simulated. Their performance using Nafion-212 with humidified H[subscript 2] and Air at 80 °C with the ANSYS Fluent Fuel Cell module software was evaluated. Novel interdigitated designs were optimized by obeying biologically inspired branching rules. These rules allow for more mathematically formal descriptions of flow field designs, enabling relatively simple optimization. The channel to land ratio was kept equivalent between designs with typical values between 0.8 and 1.0. The pressure drop and the current density distribution were monitored for each design on both anode and cathode sides. The most promising designs are expected to exhibit lower pressure drop however, low pressure drop can also be an indication of potential water flooding at higher operating current density. A biologically inspired interdigitated design with 9 inlet channels exhibited reduced pressure drop and improved current density distribution compared to all other interdigitated designs evaluated in this study. The simulated fuel cell performance data at ambient pressure with humidified H[subscript 2] and air compares well with the experimental data using a single serpentine flow field design.

Contributors

Agent

Created

Date Created
  • 2015

156403-Thumbnail Image.png

EV battery performance in the desert area and development of a new drive cycle for Arizona

Description

Commercial Li-ion cells (18650: Li4Ti5O12 anodes and LiCoO2 cathodes) were subjected to simulated Electric Vehicle (EV) conditions using various driving patterns such as aggressive driving, highway driving, air conditioning load,

Commercial Li-ion cells (18650: Li4Ti5O12 anodes and LiCoO2 cathodes) were subjected to simulated Electric Vehicle (EV) conditions using various driving patterns such as aggressive driving, highway driving, air conditioning load, and normal city driving. The particular drive schedules originated from the Environment Protection Agency (EPA), including the SC-03, UDDS, HWFET, US-06 drive schedules, respectively. These drive schedules have been combined into a custom drive cycle, named the AZ-01 drive schedule, designed to simulate a typical commute in the state of Arizona. The battery cell cycling is conducted at various temperature settings (0, 25, 40, and 50 °C). At 50 °C, under the AZ-01 drive schedule, a severe inflammation was observed in the cells that led to cell failure. Capacity fading under AZ-01 drive schedule at 0 °C per 100 cycles is found to be 2%. At 40 °C, 3% capacity fading is observed per 100 cycles under the AZ-01 drive schedule. Modeling and prediction of discharge rate capability of batteries is done using Electrochemical Impedance Spectroscopy (EIS). High-frequency resistance values (HFR) increased with cycling under the AZ-01 drive schedule at 40 °C and 0 °C. The research goal for this thesis is to provide performance analysis and life cycle data for Li4Ti5O12 (Lithium Titanite) battery cells in simulated Arizona conditions. Future work involves an evaluation of second-life opportunities for cells that have met end-of-life criteria in EV applications.

Contributors

Agent

Created

Date Created
  • 2018

158346-Thumbnail Image.png

Fabrication and Characterization of TiO2-PMMA Composite Fibers for Photocatalytic Environmental Remediation

Description

Photocatalytic activity of titanium dioxide (titania or TiO2) offers enormous potential in solving energy and environmental problems. Immobilization of titania nanoparticles on inert substrates is an effective way of utilizing

Photocatalytic activity of titanium dioxide (titania or TiO2) offers enormous potential in solving energy and environmental problems. Immobilization of titania nanoparticles on inert substrates is an effective way of utilizing its photocatalytic activity since nanoparticles enable high mass-transport, and immobilization avoids post-treatment separation. For competitive photocatalytic performance, the morphology of the substrate can be engineered to enhance mass-transport and light accessibility. In this work, two types of fiber architectures (i.e., dispersed polymer/titania phase or D-phase, and multi-phase polymer-core/composite-shell fibers or M-phase) were explored as effective substrate solutions for anchoring titania. These fibers were fabricated using a low-cost and scalable fiber spinning technique. Polymethyl methacrylate (PMMA) was selected as the substrate material due to its ultraviolet (UV) transparency and stability against oxidative radicals. The work systematically investigates the influence of the fiber porosity on mass-transport and UV light scattering. The properties of the fabricated fiber systems were characterized by scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET), UV-vis spectrophotometry (UV-vis), and mechanical analysis. The photocatalytic performance was characterized by monitoring the decomposition of methylene blue (MB) under UV (i.e., 365 nm) light. Fabrication of photocatalytic support structures was observed to be an optimization problem where porosity improved mass transport but reduced UV accessibility. The D-phase fibers demonstrated the highest MB degradation rate (i.e., 0.116 min-1) due to high porosity (i.e., 33.2 m2/g). The M-phase fibers reported a better degradation rate compared to a D-phase fibers due to higher UV accessibility efficiency.

Contributors

Agent

Created

Date Created
  • 2020

155734-Thumbnail Image.png

Analyzing the performance of lithium-ion batteries for plug-in hybrid electric vehicles and second-life applications

Description

The automotive industry is committed to moving towards sustainable modes of transportation through electrified vehicles to improve the fuel economy with a reduced carbon footprint. In this context, battery-operated hybrid,

The automotive industry is committed to moving towards sustainable modes of transportation through electrified vehicles to improve the fuel economy with a reduced carbon footprint. In this context, battery-operated hybrid, plug-in hybrid and all-electric vehicles (EVs) are becoming commercially viable throughout the world. Lithium-ion (Li-ion) batteries with various active materials, electrolytes, and separators are currently being used for electric vehicle applications. Specifically, lithium-ion batteries with Lithium Iron Phosphate (LiFePO4 - LFP) and Lithium Nickel Manganese Cobalt Oxide (Li(NiMnCo)O2 - NMC) cathodes are being studied mainly due to higher cycle life and higher energy density values, respectively. In the present work, 26650 Li-ion batteries with LFP and NMC cathodes were evaluated for Plug-in Hybrid Electric Vehicle (PHEV) applications, using the Federal Urban Driving Schedule (FUDS) to discharge the batteries with 20 A current in simulated Arizona, USA weather conditions (50 ⁰C & <10% RH). In addition, 18650 lithium-ion batteries (LFP cathode material) were evaluated under PHEV mode with 30 A current to accelerate the ageing process, and to monitor the capacity values and material degradation. To offset the high initial cost of the batteries used in electric vehicles, second-use of these retired batteries is gaining importance, and the possibility of second-life use of these tested batteries was also examined under constant current charge/discharge cycling at 50 ⁰C.

The capacity degradation rate under the PHEV test protocol for batteries with NMC-based cathode (16% over 800 cycles) was twice the degradation compared to batteries with LFP-based cathode (8% over 800 cycles), reiterating the fact that batteries with LFP cathodes have a higher cycle life compared to other lithium battery chemistries. Also, the high frequency resistance measured by electrochemical impedance spectroscopy (EIS) was found to increase significantly with cycling, leading to power fading for both the NMC- as well as LFP-based batteries. The active materials analyzed using X-ray diffraction (XRD) showed no significant phase change in the materials after 800 PHEV cycles. For second-life tests, these batteries were subjected to a constant charge-discharge cycling procedure to analyze the capacity degradation and materials characteristics.

Contributors

Agent

Created

Date Created
  • 2017

154987-Thumbnail Image.png

Design and development of electrochemical cell for converting carbon dioxide to useful fuel

Description

The majority of the natural issues the world is confronting today is because of our dependence on fossil fuels and the increase in CO2 emissions. The alternative solution for this

The majority of the natural issues the world is confronting today is because of our dependence on fossil fuels and the increase in CO2 emissions. The alternative solution for this problem is the use of renewable energy for the energy production, but these are uncertain energy sources. So, the combination of reducing carbon dioxide with the use of renewable energy sources is the finest way to mitigate this problem. Electrochemical reduction of carbon dioxide (ERC) is a reasonable approach as it eliminates as well as utilizes the carbon dioxide as a source for generating valuable products.

In this study, development of electrochemical reactor, characterization of membrane electrode assembly (MEA) and analysis of electrochemical reduction of carbon dioxide (ERC) is discussed. Electrodes using various catalyst materials in solid polymer based electrolyte (SPE) along with gas diffusion layer (GDL) are developed. The prepared membrane electrodes are characterized under ex-situ conditions using scanning electron microscopy (SEM). The membranes are later placed in the electrochemical reactor for the in-situ characterization to assess the performance of the membrane electrode assembly.

The electrodes are processed by airbrushing the metal particles on the nafion membrane and then are electrochemically characterized by linear sweep voltammetry. The anode was kept constant with platinum whereas the cathode was examined with compositions of different metal catalysts. The products formed subsequently are analyzed using gas chromatography (GC) and Residual gas analysis (RGA). Hydrogen (H2) and carbon monoxide (CO) are detected using GC while the hydrocarbons are detected by performing quantitative analysis using RGA. The preliminary experiments gave very encouraging results. However, more work needs to be done to achieve new heights.

Contributors

Agent

Created

Date Created
  • 2016

154802-Thumbnail Image.png

Performance evaluation and characterization of lithium-ion cells under simulated PHEVs' drive cycles

Description

Increasing demand for reducing the stress on fossil fuels has motivated automotive industries to shift towards sustainable modes of transport through electric and hybrid electric vehicles. Most fuel efficient cars

Increasing demand for reducing the stress on fossil fuels has motivated automotive industries to shift towards sustainable modes of transport through electric and hybrid electric vehicles. Most fuel efficient cars of year 2016 are hybrid vehicles as reported by environmental protection agency. Hybrid vehicles operate with internal combustion engine and electric motors powered by batteries, and can significantly improve fuel economy due to downsizing of the engine. Whereas, Plug-in hybrids (PHEVs) have an additional feature compared to hybrid vehicles i.e. recharging batteries through external power outlets. Among hybrid powertrains, lithium-ion batteries have emerged as a major electrochemical storage source for propulsion of vehicles.

In PHEVs, batteries operate under charge sustaining and charge depleting mode based on torque requirement and state of charge. In the current article, 26650 lithium-ion cells were cycled extensively at 25 and 50 oC under charge sustaining mode to monitor capacity and cell impedance values followed by analyzing the Lithium iron phosphate (LiFePO4) cathode material by X-ray diffraction analysis (XRD). High frequency resistance measured by electrochemical impedance spectroscopy was found to increase significantly under high temperature cycling, leading to power fading. No phase change in LiFePO4 cathode material is observed after 330 cycles at elevated temperature under charge sustaining mode from the XRD analysis. However, there was significant change in crystallite size of the cathode active material after charge/discharge cycling with charge sustaining mode. Additionally, 18650 lithium-ion cells were tested under charge depleting mode to monitor capacity values.

Contributors

Agent

Created

Date Created
  • 2016