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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 559 records · Page 31
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Electrochemical reduction of ammonia-captured CO 2 to CO over a nickel single-atom catalyst

Carbon reactive capture and conversion offers a sustainable route to valuable chemicals and fuels while aiding Green House Gas (GHG) reduction. Direct electrochemical conversion of capture solutions like bicarbonate avoids the energy demands of conventional CO 2 regeneration. Ammonium bicarbonate (NH 4 HCO 3 ) is particularly attractive due to its low decomposition temperature and ability to supply in situ CO 2 from dilute sources without requiring purified CO 2 . Meanwhile, single-atom catalysts (SACs) with nitrogen-coordinated metal sites further enhance CO 2 reduction efficiency using Earth-abundant materials. In this study, we demonstrate a nickel single-atom catalyst (Ni-SAC)-based electrolyzer that utilizes NH 4 HCO 3 as the CO 2 source, achieving significantly improved CO production performance compared to the conventional silver cathodes used in the CO 2 reduction reaction (CO 2 RR) to produce CO. The Ni-SAC cathode exhibited a Faradaic efficiency of 60.1% for CO production at −200 mA cm −2 , while the silver cathode achieved a Faradaic efficiency of only 2%, likely due to ammonium-induced poisoning. Furthermore, the integration of a customized microporous layer onto the electrode significantly increased the Faradaic efficiency from 64% to 83% at −100 mA cm −2 , emphasizing the crucial role of electrode structure optimization in enhancing CO selectivity. These findings demonstrate a sustainable and economically viable strategy for green CO production directly from CO 2 capture solutions.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2013

Surface Exchange and Bulk Diffusivity of LSCF as SOFC Cathode: Electrical Conductivity Relaxation and Isotope Exchange Characterizations

The oxygen diffusion coefficient (D) and surface exchange coefficient (k) of a typical SOFC cathode material, La{sub 0.6}Sr{sub 0.4}Co{sub 0.2}Fe{sub 0.8}O{sub 3-δ} (LSCF) were characterized by both electrical conductivity relaxation (ECR) and oxygen isotope exchange (IE) methods. Conductivity relaxation experiments were conducted at 800°C for small step changes in partial pressure of oxygen (P{sub O{sub 2}} ), both decreasing and increasing, from 0.02 atm to 0.20 atm. The results revealed P{sub O{sub 2}} dependent hysteresis with the reduction process requiring more equilibration time than oxidation. Analysis of the experimental data indicated that the surface exchange coefficient is a function of the final oxygen partial pressure in an isothermal system. In addition, both forward and backward oxygen reduction reaction constants, which are vital for the fundamental understanding of SOFC cathode reaction mechanisms, are investigated based on the relationship between surface exchange coefficient and P{sub O{sub 2}} . The direct comparisons between the results from both ECR and IE were presented and the possible experimental errors in both methods were discussed.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2024

Carbon-Binder Optimization for Lithium-Ion Battery Extreme Fast Charge

Battery performance is strongly correlated with electrode microstructure and weight loading of the electrode components. Among them are the carbon-black and binder additives that enhance effective conductivity and provide mechanical integrity. However, these both reduce effective ionic transport in the electrolyte phase and reduce energy density. Therefore, an optimal additive loading is required to maximize performance, especially for fast charging where ionic transport is essential. Such optimization analysis is however challenging due to the nanoscale imaging limitations that prevent characterizing this additive phase and thus quantifying its impact on performance. Herein, an additive-phase generation algorithm has been developed to remedy this limitation and identify percolation threshold used to define a minimal additive loading. Improved ionic transport coefficients from reducing additive loading has been then quantified through homogenization calculation, macroscale model fitting, and experimental symmetric cell measurement, with good agreement between the methods. Rate capability test demonstrates capacity improvement at fast charge at the beginning of life, from 37% to 55%, respectively for high and low additive loading during 6C CC charging, in agreement with macroscale model, and attributed to a combination of lower cathode impedance, reduced electrode tortuosity and cathode thickness.

carbon-binder additives↗
DOE OSTI2023

Neutron imaging the spatial progression of chemical oxidation of lithium-ion cathode material in a packed bed reactor

Emerging electrochemical systems relevant to energy applications including redox targeted flow batteries rely on chemical redox of solid electroactive materials using dissolved redox couples. One configuration to facilitate contact between the redox shuttles and solid material which is volume efficient is a packed bed reactor. While methods have been reported to assess the overall progression by analysis of the packed bed reactor effluent, herein analysis of the spatial progression of the chemical redox will be reported. Combination of neutron and x-ray tomography enabled assessing the pore and particle structure in the packed bed reactor and the spatial homogeneity of the reaction at different overall extents of conversion of the reactor bed. Finally, these characterization tools provide methods to probe the chemical redox processes occurring within the reactor environment.

25 ENERGY STORAGE↗
DOE OSTI2022

Recovering carbon losses in CO 2 electrolysis using a solid electrolyte reactor

The practical implementation of electrochemical CO 2 reduction technology is greatly challenged by notable CO 2 crossover to the anode side, where the crossed-over CO 2 is mixed with O 2 , via interfacial carbonate formation in traditional CO 2 electrolysers. Here we report a porous solid electrolyte reactor strategy to efficiently recover these carbon losses. Furthermore, by creating a permeable and ion-conducting sulfonated polymer electrolyte between cathode and anode as a buffer layer, the crossover carbonate can combine with protons generated from the anode to re-form CO 2 gas for reuse without mixing with anodic O 2 . Using a silver nanowire catalyst for CO 2 reduction to CO, we demonstrated up to 90% recovery of the crossover CO 2 in an ultrahigh gas purity form (>99%), while delivering over 90% CO Faradaic efficiency under a 200 mA cm -2 current. A high continuous CO 2 conversion efficiency of over 90% was achieved by recycling the recovered CO 2 to the CO 2 input stream.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Super-resolving microscopy images of Li-ion electrodes for fine-feature quantification using generative adversarial networks

Abstract For a deeper understanding of the functional behavior of energy materials, it is necessary to investigate their microstructure, e.g., via imaging techniques like scanning electron microscopy (SEM). However, active materials are often heterogeneous, necessitating quantification of features over large volumes to achieve representativity which often requires reduced resolution for large fields of view. Cracks within Li-ion electrode particles are an example of fine features, representative quantification of which requires large volumes of tens of particles. To overcome the trade-off between the imaged volume of the material and the resolution achieved, we deploy generative adversarial networks (GAN), namely SRGANs, to super-resolve SEM images of cracked cathode materials. A quantitative analysis indicates that SRGANs outperform various other networks for crack detection within aged cathode particles. This makes GANs viable for performing super-resolution on microscopy images for mitigating the trade-off between resolution and field of view, thus enabling representative quantification of fine features.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2012

An intermediate-temperature solid oxide fuel cell with electrospun nanofiber cathode

Lanthanum strontium cobalt ferrite (LSCF) nanofibers have been fabricated by the electrospinning method and used as the cathode of an intermediate-temperature solid oxide fuel cell (SOFC) with yttria-stabilized zirconia (YSZ) electrolyte. The three-dimensional nanofiber network cathode has several advantages: (i) high porosity; (ii) high percolation; (iii) continuous pathway for charge transport; (iv) good thermal stability at the operating temperature; and (v) excellent scaffold for infiltration. The fuel cell with the monolithic LSCF nanofiber cathode exhibits a power density of 0.90 W cm -2 at 1.9 A cm -2 at 750 °C. The electrochemical performance of the fuel cell has been further improved by infiltration of 20 wt% of gadolinia-doped ceria (GDC) into the LSCF nanofiber cathode. The fuel cell with the LSCF–20% GDC composite cathode shows a power density of 1.07 W cm -2 at 1.9 A cm -2 at 750 °C. The results obtained show that one-dimensional nanostructures such as nanofibers hold great promise as electrode materials for intermediate-temperature SOFCs.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2016

Method of detecting defects in ion exchange membranes of electrochemical cells by chemochromic sensors

A method of detecting defects in membranes such as ion exchange membranes of electrochemical cells. The electrochemical cell includes an assembly having an anode side and a cathode side with the ion exchange membrane in between. In a configuration step a chemochromic sensor is placed above the cathode and flow isolation hardware lateral to the ion exchange membrane which prevents a flow of hydrogen (H.sub.2) between the cathode and anode side. The anode side is exposed to a first reactant fluid including hydrogen. The chemochromic sensor is examined after the exposing for a color change. A color change evidences the ion exchange membrane has at least one defect that permits H.sub.2 transmission therethrough.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2026

Translating Fundamental Insights into Ag-Based Bimetallic Electrocatalysts to Anion-Exchange Membrane Fuel Cells

To address challenges of high costs and scalability for fuel cells, it is essential to develop af-fordable and earth-abundant materials that are Pt-group-metal (PGM)-free. Recent advance-ments in PGM-free electrocatalysis for the oxygen reduction reaction (ORR) in alkaline media show that high catalyst loadings are needed to achieve high reaction rates; however, there are associated mass transport limitations. To address this issue, we develop low-loading ionomer-less Ag-bimetallic thin films by alloying with 3d block elements or Sn. We bridge knowledge from fundamental rotating disk electrode (RDE) studies to gas-diffusion cathodes in high-temperature anion-exchange membrane fuel cells (HT-AEMFCs), resulting in high-activity ORR catalysis and peak power densities up to 1.2 W cm-² geo for the Ag-Sn and Ag-Co alloys. Here, experimental post-characterization and theoretical calculations reveal small Co or Sn oxide nano-islands on Ag as likely active sites enhancing ORR activity, ultimately offering these low-loading PGM-free ORR materials as a viable path towards sustainable energy conversion.

Catalysts↗
DOE OSTI2022

Predicting Oxygen Off-Stoichiometry and Hydrogen Incorporation in Complex Perovskite Oxides

Chemically and structurally complex solid compounds, including those with significant off-stoichiometry, are rapidly extending new material functionality across a variety of applications. Accelerated development of these compounds requires accurate predictions of material defect properties including effective defect formation energies and equilibrium defect concentrations. Traditional first-principles approaches typically examine dilute defect concentrations and relatively ordered atomic structures to identify the lowest energy defect sites. These approaches are rarely suitable for describing the disorder present in these systems and its influence on defect formation, which can lead to unphysically large predictions for defect concentrations. Here, we demonstrate a new method to accurately predict the temperature and pressure dependence of oxygen vacancy concentrations and proton interstitial concentrations in complex oxides. This method extends standard dilute defect calculations to incorporate atomic and magnetic disorder, employs the ensemble descriptions of defect sites resulting in improved predictions of defect formation energies, and accounts for effects beyond the dilute defect limit. To demonstrate our method, we show that the predicted defect concentrations in perovskites used as ceramic fuel cell cathodes, including Ba0.5Sr0.5Fe0.8Zn0.2O3-d, Ba0.5Sr0.5Co0.8Fe0.2O3-d, and BaCo1-x-y-zFexZryYzO3-d, are in good agreement with experimental values, thereby opening the door for predictive design of complex oxides by these applications.

DFT↗
DOE OSTI2017

A High Performance Low Temperature Direct Carbon Fuel Cell

A high performance direct carbon fuel cell is developed, where Ni-Gd 0.1 Ce 0.9 O 2-x cermet, a molten carbonate composite, and Sm 0.5 Sr 0.5 CoO 3 are used as anode, electrolyte, and cathode, respectively. The cell can be operated at relatively low temperatures with power densities of 188, 108 and 48 mWcm -2 being achieved at 600, 550, and 500°C, respectively, when graphite-carbonate and CO 2 -O 2 mixture are used as fuel and oxidant.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2018

Anion Exchange Membrane Electrolyzers as Alternative for Upgrading of Biomass-Derived Molecules

Upgrading biomass derived platform molecules to fuels or chemicals provides a unique alternative for the substitution of fossil sources with renewables. Electrochemical reduction (ECR) is one of the upgrading technologies, alternative to catalytic reduction, which only requires electricity as the energy input, which can be derived from carbon free energy sources. Moreover, ECR does not require external addition of hydrogen, as this can be generated in-situ. In this work an anion exchange membrane (AEM) electrolyte assembly (MEA) has been tested for the efficient reduction of biomass derived molecules, and compared with a cation exchange membrane (CEM) MEA. The cathode electrocatalyst has been modified with the addition of hydrophobicity and anion exchange ionomers, and incorporated onto an anion exchange membrane. Electrochemical experiments were performed with a metal free electrocatalyst in the presence and absence of surrogate compounds. The results showed that changes in the catalyst formulation can increase the overpotential for the competing hydrogen evolution reaction (HER), while significantly enhancing the reduction of the organic molecules. Bulk electrolysis experiments demonstrated higher efficiencies for furfural ECR in an AEM-MEA vs. AEM-CEM, reaching conversions up to 94% at 50 mA cm 2 and in the absence of supporting electrolyte. Moreover, AEM-MEA was able to facilitate water management during the reduction process and contribute to the separation of small carboxylic acids.

09 BIOMASS FUELS↗
DOE OSTI2019

Pulsed anodic arc discharge for the synthesis of carbon nanomaterials

Pulsed arc discharges can improve arc control and tailor the ablation process in the production of 1D and 2D nanostructures from carbon anodes. In this work, low-dimensional carbon nanoparticles have been generated by means of anodic arc discharge in helium atmosphere excited with a square-wave modulated signal (1–5 Hz, 10% duty cycle). The discharges were performed between two graphite electrodes with maximal peak current of 250 A and maximal voltage of 65 V. The erosion rates and conversion efficiency of the ablated anode are compared to reference samples grown in DC steady arc mode. Ablation rates in pulsed arcs are typically of the order of 1 mg/s. Combination of fast Langmuir probe diagnostics and optical emission spectroscopy provided plasma parameters of the discharges at the arc column. Ranges of 10 16 –10 17 m -3 for electron density and 0.5–2.0 eV for electron temperature are estimated. The obtained samples were characterized with Raman spectroscopy and scanning electron microscopy. The deposit on the cathode after pulsed arc consisted of carbon nanostructures such as graphene nano-platelets and carbon nanotubes. Erosion dynamics of pulsed arc discharge has been described in terms of a global model and compared to steady arc discharge. A correlation is identified among discharge regimes, optical emission patterns and ablation modes. In conclusion, pulsed anodic arc discharge is a very efficient source of carbon nanomaterials. The large control of the discharge characteristics will permit to tailor accurately the production and the properties of carbon nanotubes and graphene. Here, this deposition method is promising for the fabrication of semiconducting nanomaterials with tuneable electrical and optical properties.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Carbon Nanotubes: Applications to Energy Storage Devices

Carbon nanotubes (CNTs) are an extraordinary discovery in the area of science and technology. Engineering them properly holds the promise of opening new avenues for future development of many other materials for diverse applications. Carbon nanotubes have open structure and enriched chirality, which enable improvements the properties and performances of other materials when CNTs are incorporated in them. Energy storage systems have been using carbon nanotubes either as an additive to improve electronic conductivity of cathode materials or as an active anode component depending upon structural and morphological specifications. Furthermore, they have also been used directly as the electrode material in supercapacitors and fuel cells. Therefore, CNTs demand a huge importance due to their underlying properties and prospective applications in the energy storage research fields. There are different kinds of carbon nanotubes which have been successfully used in batteries, supercapacitors, fuel cells and other energy storage systems. This chapter focuses on the role of CNTs in the different energy storage and conversion systems and impact of their structure and morphology on the electrochemical performances and storage mechanisms.

Amin, Ruhul↗
DOE OSTI2013

In Situ Foaming of Porous (La 0.6 Sr 0.4 ) 0.98 (Co 0.2 Fe 0.8 ) O 3-δ (LSCF) Cathodes for Solid Oxide Fuel Cell Applications

A binder system containing polyurethane precursors was used to in situ foam (direct foam) a (La{sub 0.6}Sr{sub 0.4}){sub 0.98} (Co{sub 0.2} Fe{sub 0.8}) O{sub 3-{ delta}} (LSCF) composition for solid oxide fuel cell (SOFC) cathode applications. The relation between in situ foaming parameters on the final microstructure and electrochemical properties was characterized by microscopy and electrochemical impedance spectroscopy (EIS), respectively. The optimal porous cathode architecture was formed with a 70 vol% solids loading within a polymer precursor composition with a volume ratio of 8:4:1 (isocyanate: PEG: surfactant) in a terpineol-based ink vehicle. The resultant microstructure displayed a broad pore size distribution with highly elongated pore structure.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2016

Electrochemically Smart Bimetallic Materials Featuring Group 11 Metals: In-situ Conductive Network Generation and Its Impact on Cell Capacity

Our results for this program “Electrochemically smart bimetallic materials featuring Group 11 metals: in-situ conductive matrix generation and its impact on battery capacity, power and reversibility” have been highly successful: 1) we demonstrated material structures which generated in-situ conductive networks through electrochemical activation with increases in conductivity up to 10,000 fold, 2) we pioneered in situ analytical methodology to map the cathodes at several stages of discharge through the use of Energy Dispersive X-ray Diffraction (EDXRD) to elucidate the kinetic dependence of the conductive network formation, and 3) we successfully designed synthetic methodology for direct control of material properties including crystallite size and surface area which showed significant impact on electrochemical behavior.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2016

Methods for using novel cathode and electrolyte materials for solid oxide fuel cells and ion transport membranes

Methods using novel cathode, electrolyte and oxygen separation materials operating at intermediate temperatures for use in solid oxide fuel cells and ion transport membranes include oxides with perovskite related structures and an ordered arrangement of A site cations. The materials have significantly faster oxygen kinetics than in corresponding disordered perovskites.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2016

Solid oxide fuel cell systems with hot zones having improved reactant distribution

A Solid Oxide Fuel Cell (SOFC) system having a hot zone with a center cathode air feed tube for improved reactant distribution, a CPOX reactor attached at the anode feed end of the hot zone with a tail gas combustor at the opposing end for more uniform heat distribution, and a counter-flow heat exchanger for efficient heat retention.

30 DIRECT ENERGY CONVERSION↗