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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 109 records · Page 6
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↗
DOE OSTI2020

Enabling safe aqueous lithium ion open batteries by suppressing oxygen reduction reaction

Abstract Due to the non-flammable nature of water-based electrolytes, aqueous lithium-ion batteries are resistant to catching fire. However, they are not immune to the risk of explosion, since the sealing structure adopted by current batteries limits the dissipation of heat and pressure within the cells. Here, we report a safe aqueous lithium-ion battery with an open configuration using water-in-salt electrolytes and aluminum oxide coated anodes. The design can inhibit the self-discharge by substantially suppressing the oxygen reduction reaction on lithiated anodes and enable good cycle performance over 1000 times. Our study may open a pathway towards safer lithium-ion battery designs.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Application of machine learning to discover new intermetallic catalysts for the hydrogen evolution and the oxygen reduction reactions

The adsorption energies for hydrogen, oxygen, and hydroxyl were calculated by means of density functional theory on the lowest energy surface of 24 pure metals and 332 binary intermetallic compounds with stoichiometries AB, A 2 B, and A 3 B taking into account the effect of biaxial elastic strains. This information was used to train two random forest regression models, one for the hydrogen adsorption and another for the oxygen and hydroxyl adsorption, based on 9 descriptors that characterized the geometrical and chemical features of the adsorption site as well as the applied strain. All the descriptors for each compound in the models could be obtained from physico-chemical databases. The random forest models were used to predict the adsorption energy for hydrogen, oxygen, and hydroxyl of ≈2700 binary intermetallic compounds with stoichiometries AB, A 2 B, and A 3 B made of metallic elements, excluding those that were environmentally hazardous, radioactive, or toxic. This information was used to search for potential good catalysts for the HER and ORR from the criteria that their adsorption energy for H and O/OH, respectively, should be close to that of Pt. Further, this investigation shows that the suitably trained machine learning models can predict adsorption energies with an accuracy not far away from density functional theory calculations with minimum computational cost from descriptors that are readily available in physico-chemical databases for any compound. Moreover, the strategy presented in this paper can be easily extended to other compounds and catalytic reactions, and is expected to foster the use of ML methods in catalysis.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Designed Iron Single Atom Catalysts for Highly Efficient Oxygen Reduction Reaction in Alkaline and Acid Media

Abstract Single atom catalysts (SACs) have attracted much attentions due to their advantages of high catalysis efficiency and excellent selectivity. However, for industrial applications, synthesis of SACs in large and practical quantities is very important. The challenge is to develop synthesis methods with controllability and scalability. Herein, a well‐characterized and scalable method is demonstrated to synthesize atomically dispersed iron atoms coordinated with nitrogen on graphene, SAFe @ NG, with high atomic loading (≈4.6 wt%) through a one‐pot pyrolysis process. The method is scalable for the fabrication of Fe SACs with high quantities. The Fe–N–G catalyst exhibits high intrinsic oxygen reduction reaction (ORR) performance, reaching half potential of 0.876 and 0.702 V in alkaline and acidic solutions, respectively, with excellent microstructure stability. Furthermore, the density functional theory (DFT) simulation confirms that the Fe atoms in coordination with four nitrogen atoms, FeN4, in graphene is the active center for the 4‐electron ORR process. This work demonstrates an efficient design pathway for single atom catalysts as highly active and stable electrocatalysts for high‐performance ORR applications.

Zhao, Shiyong↗
DOE OSTI2025

Permanent Nanobubbles in Water: Liquefied Hollow Carbon Spheres Break the Limiting Diffusion Current of Oxygen Reduction Reaction

Porous liquids have traditionally been designed with sterically hindered solvents. Alternatively, recent efforts rely on dispersing microporous frameworks in simpler solvents like water. Here we report a unique strategy to construct macroporous water by selectively incorporating hydrophilicity on the surfaces of hydrophobic hollow carbon spheres (HCS). Specifically, we show that the stable dispersion surface ionized HCS in water while retaining the inherent porosity. The electrocatalytic conversion of small gas molecules in aqueous electrolytes is limited by the concentration and diffusion rates of gas molecules in water. In this case, macroporous water exhibited 6 times gas uptake compared to nonporous (pure) water. Furthermore, by leveraging the high gas capacity and enhanced diffusion kinetics, the limiting diffusion current of oxygen reduction reaction (ORR) in macroporous water is 2 times that in nonporous water, offering promising prospects for sustainable energy conversion technologies.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Carbon nanodot precursors enable ultrahigh-loading copper single-atom catalysts for oxygen reduction reaction

Single-atom catalysts (SACs) have attracted significant attention in electrocatalysis due to their high metal utilization and tunable electronic structures; however, their practical implementation is often limited by poor atomic dispersion, low metal loadings (typically < 1 wt%), and insufficient anchoring of single metal atoms on catalyst supports. Herein, we report a simple and versatile strategy to synthesize copper single-atom catalysts (Cu-SACs) with ultrahigh metal loading using citric-acid-derived carbon nanodots as metal-capturing precursors. Through hydrothermal treatment followed by pyrolysis in the presence of urea, atomically dispersed copper atoms coordinated with nitrogen are incorporated into a carbon framework, achieving a Cu loading of up to 20 wt% while maintaining atomic dispersion. Notably, a significant fraction of the copper single atoms exists as Cu+–N2 coordination, which provides under-coordinated and catalytically active sites. The resulting Cu-SAC exhibits promising oxygen reduction reaction (ORR) activity in alkaline media, delivering a limiting current density comparable to that of commercial 20 wt% Pt/C with a predominant four-electron reduction pathway. Despite this high intrinsic activity, durability tests reveal gradual performance degradation under prolonged electrochemical operation, which is attributed to demetallation and aggregation of copper single atoms into metallic nanoparticles. These results demonstrate the potential of carbon nanodot-based platforms for synthesizing high-loading SACs, while underscoring the critical need to simultaneously control carbon porosity and metal–nitrogen coordination to enhance active-site accessibility and durability.

Sharma, Prakhar [University of Kentucky]↗
DOE OSTI2021

Stability of Pt Skin Intermetallic Core Catalysts and Adsorption Properties for the Oxygen Reduction Reaction

Density functional theory calculations were used to determine the stability of metal slabs consisting of a Pt surface monolayer and intermetallic supporting layers made from combinations of six transition metal elements (Pt, Fe, Co, Ni, Cu, and Ag), as a model system for Pt skin intermetallic core nanoparticle catalysts. The stability of the slabs is largely determined by strain at the interface of the Pt skin and the subsurface intermetallic, which was described by a lattice matching parameter (r). The surface charge on the Pt skin was found to be correlated with the average electronegativity (EN) of the intermetallic core, so this average EN was used as a descriptor for how the electronic coupling (or ligand effect) affects adsorption energies. A total of 46 slabs were investigated in terms of their stability, from which 10 stable slabs were selected for further studies of adsorbate binding (OOH*, O*, and OH*) that are intermediates in the oxygen reduction reaction (ORR). The correlation between all three adsorption energies and descriptors r and EN was found. Using a linear fit between our descriptors and the calculated adsorption energies, the overpotential for the ORR was obtained as a function of r and EN, from which a volcano plot was produced. The volcano peak was found at r = 0.96 or at EN = 2.025. Interestingly, neither r nor EN was a sufficient single reactivity descriptor as the data points were well off the general trend in both linear fits; this implies that both the strain effect and the ligand effect influence the adsorption energies, although they are partly correlated. The (r, EN) target peak parameters were used to screen over 241 intermetallic combinations of transition metal elements as active ORR activity. In conclusion, this analysis identified 11 intermetallic compounds which can support a Pt skin to have a high predicted ORR activity.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

High-Loading Single-Atom Catalyst via On-Surface Synthesis of a Metal-Covalent Organic Framework for Oxygen Reduction Reaction

The development of active catalysts with both high metal efficiency and use of earth abundant metals is the ultimate goal for advancing the required commercially viable and sustainable energy conversion technologies of the future. Metal-organic frameworks (MOFs) have emerged as promising candidates due to their high surface area and tunable active sites. Here, this study aims to fabricate a new type of high metal loading single-atom catalysts (SACs) based on 2D metal-organic covalent organic frameworks (MCOFs) with uniform, active and stable Fe-N 3 sites. The MCOFs were synthesized through an on-surface polymerization process using Fe and melamine as precursors. The polymerization steps were characterized using operando high-pressure scanning tunneling microscopy (HP-STM), in situ X-ray photoelectron spectroscopy (XPS), low-temperature STM (LT-STM), and computational calculations. The synthesized MCOFs demonstrated favorable adsorption and activation of O 2 at the Fe-N 3 sites, and it is predicted to be active for the oxygen reduction reaction (ORR). The surface chemistry and functionality of 2D MCOFs can be rationally designed by varying the metal atoms and organic linkers, offering a versatile platform for diverse applications.

25 ENERGY STORAGE↗
DOE OSTI2022

An Unbalanced Battle in Excellence: Revealing Effect of Ni/Co Occupancy on Water Splitting and Oxygen Reduction Reactions in Triple–Conducting Oxides for Protonic Ceramic Electrochemical Cells

Porous electrodes that conduct electrons, protons, and oxygen ions with dramatically expanded catalytic active sites can replace conventional electrodes with sluggish kinetics in protonic ceramic electrochemical cells. In this work, a strategy is utilized to promote triple conduction by facilitating proton conduction in praseodymium cobaltite perovskite through engineering non-equivalent B-site Ni/Co occupancy. Surface infrared spectroscopy is used to study the dehydration behavior, which proves the existence of protons in the perovskite lattice. The proton mobility and proton stability are investigated by hydrogen/deuterium (H/D) isotope exchange and temperature-programmed desorption. It is observed that the increased nickel replacement on the B-site has a positive impact on proton defect stability, catalytic activity, and electrochemical performance. This doping strategy is demonstrated to be a promising pathway to increase catalytic activity toward the oxygen reduction and water splitting reactions. The chosen PrNi 0.7 Co 0.3 O 3–δ oxygen electrode demonstrates excellent full-cell performance with high electrolysis current density of –1.48 A cm –2 at 1.3 V and a peak fuel-cell power density of 0.95 W cm –2 at 600 °C and also enables lower-temperature operations down to 350 °C, and superior long-term durability.

08 HYDROGEN↗
DOE OSTI2020

Nanosized Zirconium Porphyrinic Metal–Organic Frameworks that Catalyze the Oxygen Reduction Reaction in Acid

Porphyrinic metal–organic frameworks (PMOFs) are very appealing electrocatalytic materials, in part, due to their highly porous backbone, well-defined and dispersed metal active sites, and their long-range order. Herein a series of (Co)PCN222 (PCN: porous coordination network) (nano)particles with different sizes are successfully prepared by coordination modulation synthesis. These particles exhibit stability in 0.1 M HClO 4 electrolyte with no obvious particle size or compositional changes observed after being soaked for 3 days in the electrolyte or during electrocatalysis. This long-term stability enables the in-depth investigation into the electrocatalytic oxygen reduction, and it is further demonstrated that the (Co)PCN222 particle size correlates with its catalytic activity. Of the three particle sizes evaluated (characteristic length scales of 200, 500, and 1000 nm), the smallest size demonstrates the highest mass activity while the largest size has the highest surface area normalized activity. Together these results highlight the importance of determining the structural stability of framework catalysts and provide insights into the important roles of particle size, opening new avenues to investigate and improve the electrocatalytic performance of this class of framework material.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

An improved oxygen reduction reaction activity and CO 2 -tolerance of La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ achieved by a surface modification with barium cobaltite coatings

Solid oxide fuel cells (SOFCs) cathode often suffers from the poisoning effect of the contaminants commonly encountered in air such as CO 2 . Here we report an effective approach to enhancing the activity and CO 2 tolerance of the state-of-the-art La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (LSCF) cathode enabled by a coating of BaCoO 3-δ (BCO), as verified by the electrochemical testings, Raman analyses, and density functional theory calculations. When surface modified with a thin-film BCO coating, LSCF displays a much enhanced ORR activity and an improved durability against CO 2 . For example, anode supported SOFCs with the LSCF cathode coated with BCO coatings show a remarkable peak power density (Pmax) of 0.41 Wcm -2 and a significantly reduced degradation rate in current density of ~0.08% h -1 at 0.8 V and 700 °C for a period of 300 hs when humidified H2 (with 3 vol%H2O) was used as fuel and air with 8 vol% CO 2 as oxidant. The demonstrated performance is improved when compared with those of the cells with a blank LSCF electrode (a Pmax of ~0.36 Wcm -2 and a degradation rate of ~0.15% h -1 ) under the same conditions. Furthermore, the adsorption energy calculations suggests that BCO coating makes CO 2 adsorption much weaker than LSCF (-0.54 eV versus -1.07 eV).

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2025

Unsupported and carbon-supported silver catalysts for oxygen reduction reaction in alkaline media

Quick and easy Ag catalysts preparation via wet chemical synthesis method using only reducing agent (pure-Ag); reducing agent and citric acid as the capping agent (Ag-CA); and carbon support (KetjenBlack 600J), capping agent, and the reducing agent (Ag/C) is demonstrated. The Ag-based electrocatalysts are characterized by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) with energy-dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis, and X-ray photoelectron spectroscopy (XPS). The electrocatalytic activity of Ag catalysts for O 2 reduction reaction (ORR) in 1 M KOH is evaluated using the rotating (ring)-disc electrode method. SEM and HAADF-STEM results show that the unsupported pure-Ag and Ag-CA catalysts consist mainly of big agglomerates, and Ag/C has the smallest agglomerates and some sub-3 nm Ag nanoparticles. The XPS results reveal that Ag in all the catalysts is in the metallic form (Ag 0 ). Despite consisting of big agglomerates, the Ag-CA catalyst exhibits similar ORR electrocatalytic activity to that of Ag/C. Ag-CA (unsupported) shows the lowest hydrogen peroxide yield. These results are of great importance for the development of Ag-based catalysts that can be prepared in a fast, simple and easily up scalable fashion, for anion exchange membrane fuel cells.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Breaking the Linear Scaling Relations for the Oxygen Reduction Reaction with a Dual‐Atom Catalyst Composed of a MnFe‐Porphyrrole Aerogel

Bimetallic catalysts offer enhanced catalytic performance through synergistic interactions between the two metals, allowing them to break the linear scaling relations and reach high electrocatalytic activity. This study presents bimetallic aerogel-based catalyst synthesized as a covalent, three-dimensional framework containing neighboring iron and manganese sites. The aerogel structure provides a high surface area and porosity, facilitating an ultra-high active site density and efficient mass transport. The MnFe porphyrrole's unique structure is obtained by alternately linking Mn-porphyrin and Fe-corrole complexes. It exhibited outstanding performance with an onset potential of 0.99 V RHE . Comparative studies with a free-base Fe porphyrrole catalyst (E onset 0.97 V RHE ) revealed that while Mn incorporation led to only a slight improvement in half-cell performance, it resulted in significantly enhanced performance in anion exchange membrane fuel cell. The MnFe catalyst achieved an OCV of 0.97 V and a peak power density of 0.27 W cm −2 , outperforming the free-base Fe counterpart. Using density functional theory calculations, we show that the higher ORR activity of MnFe-porphyrrole is due to charge transfer between Mn and Fe atoms, which is absent in the reference free-base Fe-porphyrrole. These findings underscore the advantages of bimetallic catalysts in improving ORR activity and fuel cell efficiency by leveraging synergistic effects.

Aerogel↗
DOE OSTI2020

P-block single-metal-site tin/nitrogen-doped carbon fuel cell cathode catalyst for oxygen reduction reaction

This contribution reports the discovery and analysis of a p-block Sn-based catalyst for the electroreduction of molecular oxygen in acidic conditions at fuel cell cathodes; the catalyst is free of platinum-group metals and contains single-metal-atom actives sites coordinated by nitrogen. The prepared SnNC catalysts meet and exceed state-of-the-art FeNC catalysts in terms of intrinsic catalytic turn-over frequency and hydrogen–air fuel cell power density. The SnNC-NH 3 catalysts displayed a 40–50% higher current density than FeNC-NH 3 at cell voltages below 0.7 V. Additional benefits include a highly favourable selectivity for the four-electron reduction pathway and a Fenton-inactive character of Sn. Here, a range of analytical techniques combined with density functional theory calculations indicate that stannic Sn(iv)Nx single-metal sites with moderate oxygen chemisorption properties and low pyridinic N coordination numbers act as catalytically active moieties. The superior proton-exchange membrane fuel cell performance of SnNC cathode catalysts under realistic, hydrogen–air fuel cell conditions, particularly after NH 3 activation treatment, makes them a promising alternative to today’s state-of-the-art Fe-based catalysts.

25 ENERGY STORAGE↗