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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Pressure dependence of the oxygen reduction reaction at the platinum microelectrode/nafion interface - Electrode kinetics and mass transport

The investigation of oxygen reduction kinetics at the platinum/Nafion interface is of great importance in the advancement of proton-exchange-membrane (PEM) fuel-cell technology. This study focuses on the dependence of the oxygen reduction kinetics on oxygen pressure. Conventional Tafel analysis of the data shows that the reaction order with respect to oxygen is unity at both high and low current densities. Chronoamperometric measurements of the transport parameters for oxygen in Nafion show that oxygen dissolution follows Henry's isotherm. The diffusion coefficient of oxygen is invariant with pressure; however, the diffusion coefficient for oxygen is lower when air is used as the equilibrating gas as compared to when oxygen is used for equilibration. These results are of value in understanding the influence of O2 partial pressure on the performance of PEM fuel cells and also in elucidating the mechanism of oxygen reduction at the platinum/Nafion interface.

Parthasarathy, Arvind↗
NASA NTRS1992

The platinum microelectrode/Nafion interface - An electrochemical impedance spectroscopic analysis of oxygen reduction kinetics and Nafion characteristics

The objectives of this study were to use electrochemical impedance spectroscopy (EIS) to study the oxygen-reduction reaction under lower humidification conditions than previously studied. The EIS technique permits the discrimination of electrode kinetics of oxygen reduction, mass transport of O2 in the membrane, and the electrical characteristics of the membrane. Electrode-kinetic parameters for the oxygen-reduction reaction, corrosion current densities for Pt, and double-layer capacitances were calculated. The production of water due to electrochemical reduction of oxygen greatly influenced the EIS response and the electrode kinetics at the Pt/Nafion interface. From the finite-length Warburg behavior, a measure of the diffusion coefficient of oxygen in Nafion and diffusion-layer thickness was obtained. An analysis of the EIS data in the high-frequency domain yielded membrane and interfacial characteristics such as ionic conductivity of the membrane, membrane grain-boundary capacitance and resistance, and uncompensated resistance.

Parthasarathy, Arvind↗
NASA NTRS2020

Structural evolution, electrochemical kinetic properties, and stability of A-site doped perovskite Sr(1-x)Yb(x)CoO(3-δ)

Mixed ionic and electronic conducting (MIEC) perovskite SrCoO(3-δ) is a widely studied (electro)catalyst for the oxygen reduction reaction (ORR) and possesses different crystal structures at different temperatures. These temperature dependent phase transitions significantly impact the ordering of oxygen vacancies and electrochemical kinetic properties as well as the reliability of the related devices. Some of the crystal structures formed, e.g. hexagonal phases, turn out to be almost impermeable to oxygen gas. Therefore, it is important to stabilize the crystal structure of SrCoO(3-δ) that favors the ORR over a wide temperature range. Herein, the partial substitution of the A-site Sr with Yb is systematically studied, including synthesis, characterization and analysis of structural evolution, electrochemical kinetic properties, thermal stability, and stability in a CO2-containing atmosphere. The results indicate that Sr(0.90)Yb(0.10)CoO(3-δ) is able to stabilize the tetragonal crystal structure with less ordered oxygen vacancies, leading to polarization resistances of 0.051, 0.115 and 0.272 U sq.cm at 750, 700 and 650 °C, respectively, on symmetrical cells. Sr(0.90)Yb(0.10)CoO(3-δ) demonstrates a very stable surface oxygen vacancy distribution and electronic structure near oxygen vacancies but dissociation of adsorbed oxygen molecules into atomic oxygen is affected by surface Sr segregation, and polarization resistance degradation is mainly induced by surface Sr segregation. Furthermore, Sr(0.90)Yb(0.10)CoO(3-δ) exhibits excellent thermal stability as well as excellent recovery stability and improved polarization performance after a few pure air/CO2-containing air treatment cycles at 700 °C. However, a hysteresis behavior of polarization performance is observed at 650 °C during gas cycling treatment, which may cause long-term degradation of the Sr(0.90)Yb(0.10)CoO(3-δ) electrode. The different polarization behaviors during gas cycling treatment are induced by different sensitivities of the formed surface strontium carbonate and chemisorbed surface oxo-carbonaceous species to different operating temperatures.

electrochemical kinetic↗
NASA NTRS1989

Recent advances in solid polymer electrolyte fuel cell technology with low platinum loading electrodes

High power density fuel cell systems for defense and civilian applications are being developed. Taking into consideration the main causes for efficiency losses (activation, mass transport and ohmic overpotentials) the only fuel cell systems capable of achieving high power densities are the ones with alkaline and solid polymer electrolyte. High power densities (0.8 W/sq cm at 0.8 V and 1 A/sq cm with H2 and O2 as reactants), were already used in NASA's Apollo and Space Shuttle flights as auxiliary power sources. Even higher power densities (4 W/sq cm - i.e., 8 A sq cm at 0.5 V) were reported by the USAF/International Fuel Cells in advanced versions of the alkaline system. High power densities (approximately 1 watt/sq cm) in solid polymer electrolyte fuel cells with ten times lower platinum loading in the electrodes (i.e., 0.4 mg/sq cm) were attained. It is now possible to reach a cell potential of 0.620 V at a current density of 2 A/sq cm and at a temperature of 95 C and pressure of 4/5 atm with H2/O2 as reactants. The slope of the linear region of the potential-current density plot for this case is 0.15 ohm-sq cm. With H2/air as reactants and under the same operating conditions, mass transport limitations are encountered at current densities above 1.4 A/sq cm. Thus, the cell potential at 1 A/sq cm with H2/air as reactants is less than that with H2/O2 as reactants by 40 mV, which is the expected value based on electrode kinetics of the oxygen reduction reaction, and at 2 A/sq cm with H2/air as reactant is less than the corresponding value with H2/O2 as reactants by 250 mV, which is due to the considerably greater mass transport limitations in the former case.

Srinivasan, Supramaniam↗
NASA NTRS2013

Pt-Ni and Pt-Co Catalyst Synthesis Route for Fuel Cell Applications

Oxygen reduction reactions (ORRs) at the cathode are the rate-limiting step in fuel cell performance. The ORR is 100 times slower than the corresponding hydrogen oxidation at the anode. Speeding up the reaction at the cathode will improve fuel cell efficiency. The cathode material is generally Pt powder painted onto a substrate (e.g., graphite paper). Recent efforts in the fuel cell area have focused on replacing Pt with Pt-X alloys (where X = Co, Ni, Zr, etc.) in order to (a) reduce cost, and (b) increase ORR rates. One of these strategies is to increase ORR rates by reducing the powder size, which would result in an increase in the surface area, thereby facilitating faster reaction rates. In this work, a process has been developed that creates Pt-Ni or Pt-Co alloys that are finely divided (on the nano scale) and provide equivalent performance at lower Pt loadings. Lower Pt loadings will translate to lower cost. Precursor salts of the metals are dissolved in water and mixed. Next, the salt mixtures are dried on a hot plate. Finally, the dried salt mixture is heattreated in a furnace under flowing reducing gas. The catalyst powder is then used to fabricate a membrane electrode assembly (MEA) for electrochemical performance testing. The Pt- Co catalyst-based MEA showed comparable performance to an MEA fabri cated using a standard Pt black fuel cell catalyst. The main objective of this program has been to increase the overall efficiencies of fuel cell systems to support power for manned lunar bases. This work may also have an impact on terrestrial programs, possibly to support the effort to develop a carbon-free energy source. This catalyst can be used to fabricate high-efficiency fuel cell units that can be used in space as regenerative fuel cell systems, and terrestrially as primary fuel cells. Terrestrially, this technology will become increasingly important when transition to a hydrogen economy occurs.

Firdosy, Samad A.↗
NASA NTRS2014

Lithium-Air Cell Development

Lithium-air (Li-air) primary batteries have a theoretical specific capacity of 11,400 Wh/kg, the highest of any common metal-air system. NASA is developing Li-air technology for a Mobile Oxygen Concentrator for Spacecraft Emergencies, an application which requires an extremely lightweight primary battery that can discharge over 24 hours continuously. Several vendors were funded through the NASA SBIR program to develop Li-air technology to fulfill the requirements of this application. New catalysts and carbon cathode structures were developed to enhance the oxygen reduction reaction and increase surface area to improve cell performance. Techniques to stabilize the lithium metal anode surface were explored. Experimental results for prototype laboratory cells are given. Projections are made for the performance of hypothetical cells constructed from the materials that were developed.

Lithium-air↗
NASA NTRS2018

Design and Development of Advanced Air-Cathodes for Li-Air Battery

NASA's future missions demand high energy density batteries. Current state-of-the-art lithium-ion batteries (LIBs) reach the specific energy capacity limits (<250 Wh/kg), thus new electrochemical storage technologies are needed to meet NASA's future mission requirement of >400 Wh/kg. Battery chemistries with higher theoretical energy densities in particular, Li-metal based battery chemistries such as Li-air, are being actively pursued, but there remains a number of issues to be solved. Development of advanced and optimized air cathodes will be crucial for improving capacity retention and cycle life of Li-air battery. The microstructure of carbon substrates and the catalytic oxygen reduction of the air-cathode play critical roles in the electrochemical performance in Li-air batteries. With the development and proper design of air cathodes, the energy efficiency and energy density can be enhanced significantly. In this presentation, the results of advanced permeable air cathodes design with different substrates such as 2D carbon paper or carbon cloth, vs 3D graphene or metal foam, different high surface area carbon materials and incorporation with catalysts on oxygen reduction reactions, different porosity controlling of air cathode as well the additives in electrolyte will be presented. The cycling and rate capability performance of these air-cathodes in the Li-air cells will be discussed as well.

Wu, James J.↗
NASA NTRSDate not supplied

Development of Aluminum/Air Battery as High-Capacity Primary Battery Energy Source for SUSAN Electrofan Project

High-capacity, high-performance, and safe battery technologies are demanded by the Subsonic Single Aft eNgine (SUSAN) Electrofan concept design project under National Aeronautics and Space Administration (NASA) electrified aircraft development program. These battery technologies, including both secondary (i.e., rechargeable) batteries for hybrid/electric propulsion and primary batteries (i.e. non-rechargeable or single-use) for backup/emergency use in case of turbine engine failure, are important and vital components in SUSAN concept design. This paper is focused on aluminum (Al)-air battery, which is considered to be the most promising candidate to meet the energy goal of primary batteries for SUSAN project. However, there are challenges for Al-air batteries, including aluminum self-corrosion with hydrogen (H2) gassing and sluggish kinetics of oxygen reduction reaction (ORR) in air-cathode. In this paper, the preliminary results on investigation of electrolytes and additives on controlling aluminum self-corrosion/H2 gassing suppression and the study of air-cathode design for ORR improvement are presented and discussed.

James Wu↗
NASA NTRS1993

Experimental Observations of the Effect of Gravity Changes on Smoldering Combustion

The effects of gravity changes on the natural convection smolder characteristics of flexible polyurethane foam were determined in order to provide information on the potential onset of a smolder-initiated fire in a space-based facility. Experiments were conducted in an aircraft following parabolic trajectories providing up to 25 seconds of low gravity. Temperature histories of polyurethane foam were measured at several locations along the fuel sample interior. Results are presented and discussed for both upward and downward smoldering. Results indicate that gravity significantly effects the competition between supply of oxidizer to, and the transfer of heat to and from the reaction zone. This competition determines the characteristics of the smolder reaction. Within the reaction zone the reduction in oxygen supply in low gravity is dominant and the reaction weakens. Away from the reaction zone the reduction in convective cooling at low gravity tends to increase the material temperature. The opposite was observed at high gravity.

Torero, J. L.↗
NASA NTRS1983

Electrocatalysis of fuel cell reactions: Investigation of alternate electrolytes

Oxygen reduction and transport properties of the electrolyte in the phosphoric acid fuel cell are studied. A theoretical expression for the rotating ring-disk electrode technique; the intermediate reaction rate constants for oxygen reduction on platinum in phosphoric acid electrolyte; oxygen reduction mechanism in trifluoromethanesulfonic acid (TFMSA), considered as an alternate electrolyte for the acid fuel cells; and transport properties of the phosphoric acid electrolyte at high concentrations and temperatures are covered.

Chin, D. T.↗
NASA NTRS1991

Mathematical modeling of a nickel-cadmium battery

Extensions are presented for a mathematical model of an Ni-CD cell (Fan and White, 1991). These extensions consist of intercalation thermodynamics for the nickel electrode and oxygen generation and reduction reactions during charge and overcharge. The simulated results indicate that intercalation may be important in the nickel electrode and that including the oxygen reactions provides a means of predicting the efficiency of the cell on charge and discharge.

Fan, Deyuan↗
NASA NTRS1994

Reduction of lunar basalt 70035: Oxygen yield and reaction product analysis

Oxygen production from a lunar rock has been experimentally demonstrated for the first time. A 10 g sample of high-Ti basalt 70035 was reduced with hydrogen in seven experiments at temperatures of 900-1050 C and pressures of 14.7-150 psia. In all experiments, water evolution began almost immediately and was essentially complete in tens of minutes. Oxygen yields ranged from 2.93 to 4.61% of the starting sample weight, and showed weak dependence on temperature and pressure. Analysis of the solid samples demonstrated total reduction of Fe(2+) in ilmenite and small degrees of reduction in olivine and pyroxene. Ti O2 was also partially reduced to one or more suboxides. Data from these experiments provide a basis for predicting the yield of oxygen from lunar basalt as well as new constraints on natural reduction in the lunar regolith.

Gibson, Michael A.↗
NASA NTRS1984

Electrocatalysis of fuel cell reactions: Investigation of alternate electrolytes

Oxygen reduction and transport properties of the electrolyte in the phosphoric acid fuel cell are studied. The areas covered were: (1) development of a theoretical expression for the rotating ring disk electrode technique; (2) determination of the intermediate reaction rate constants for oxygen reduction on platinum in phosphoric acid electrolyte; (3) determination of oxygen reduction mechanism in trifluoreomethanesulfonic acid (TFMSA) which was considered as an alternate electrolyte for the acid fuel cells; and (4) the measurement of transport properties of the phosphoric acid electrolyte at high concentrations and temperatures.

Chin, D. T.↗
NASA NTRSDate not supplied

Silver Electrolysis for Disinfection of Spacecraft Potable Water: 2023 Update

Anodic dissolution of silver electrodes, or “silver electrolysis,” is being investigated as a means of introducing biocidal silver into potable water on exploration spacecraft. Last year’s paper reported a fault condition termed “electrode bridging,” in which silver deposits on interelectrode wetted materials, eventually bridging the electrode gap and providing an alternate conduction pathway that diminishes the silver output of the reactor. Since then, two strategies have been developed that prevent this fault from occurring: 1) increasing the frequency of polarity reversal and 2) separating the active surface of the electrode from the interelectrode wetted material. These strategies were tested independently, and in both cases, the reactor performed as expected with no occurrence of bridging for at least one crew-year equivalent of cumulative operation. Additional tests were conducted at varying levels of influent dissolved oxygen to better understand the nature of the cathode reaction and its impact on reactor performance. Results indicate that the primary cathode reaction is the reduction of dissolved oxygen, which could imply a dependence of reactor performance on dissolved oxygen concentration. However, it was found that at the typical oxygen concentrations anticipated for spacecraft processed water, the impact on silver electrolysis performance was negligible. Finally, multiphysics modelling of the reactor fluid mechanics and electrochemistry was undertaken to provide the capability to optimize the design of a future reactor prototype.

silver electrolysis↗
NASA NTRSDate not supplied

Silver Electrolysis for Disinfection of Spacecraft Potable Water: 2023 Update

Anodic dissolution of silver electrodes, or “silver electrolysis,” is being investigated as a means of introducing biocidal silver into potable water on exploration spacecraft. Last year’s paper reported a fault condition termed “electrode bridging,” in which silver deposits on interelectrode wetted materials, eventually bridging the electrode gap and providing an alternate conduction pathway that diminishes the silver output of the reactor. Since then, two strategies have been developed that prevent this fault from occurring: 1) increasing the frequency of polarity reversal and 2) separating the active surface of the electrode from the interelectrode wetted material. These strategies were tested independently, and in both cases, the reactor performed as expected with no occurrence of bridging for at least one crew-year equivalent of cumulative operation. Additional tests were conducted at varying levels of influent dissolved oxygen to better understand the nature of the cathode reaction and its impact on reactor performance. Results indicate that the primary cathode reaction is the reduction of dissolved oxygen, which could imply a dependence of reactor performance on dissolved oxygen concentration. However, it was found that at the typical oxygen concentrations anticipated for spacecraft processed water, the impact on silver electrolysis performance was negligible. Finally, multiphysics modelling of the reactor fluid mechanics and electrochemistry was undertaken to provide the capability to optimize the design of a future reactor prototype.

silver electrolysis↗
NASA NTRS2013

Nanostructured Platinum Alloys for Use as Catalyst Materials

A series of binary and ternary Pt-alloys, that promote the important reactions for catalysis at an alloy surface; oxygen reduction, hydrogen oxidation, and hydrogen and oxygen evolution. The first two of these reactions are essential when applying the alloy for use in a PEMFC.

Hays, Charles C.↗
NASA NTRS2015

Nanostructured Platinum Alloys for Use as Catalyst Materials

A series of binary and ternary Pt-alloys, that promote the important reactions for catalysis at an alloy surface; oxygen reduction, hydrogen oxidation, and hydrogen and oxygen evolution. The first two of these reactions are essential when applying the alloy for use in a PEMFC.

Hays, Charles C.↗