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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 505 records · Page 28
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Seawater alkalization via an energy-efficient electrochemical process for CO 2 capture

Electrochemical pH-swing strategies offer a promising avenue for cost-effective and energy-efficient carbon dioxide (CO 2 ) capture, surpassing the traditional thermally activated processes and humidity-sensitive techniques. The concept of elevating seawater’s alkalinity for scalable CO 2 capture without introducing additional chemical as reactant is particularly intriguing due to its minimal environmental impact. However, current commercial plants like chlor-alkali process or water electrolysis demand high thermodynamic voltages of 2.2 V and 1.23 V, respectively, for the production of sodium hydroxide (NaOH) from seawater. These high voltages are attributed to the asymmetric electrochemical reactions, where two completely different reactions take place at the anode and cathode. Here, we developed a symmetric electrochemical system for seawater alkalization based on a highly reversible and identical reaction taking place at the anode and cathode. We utilize hydrogen evolution reaction at the cathode, where the generated hydrogen is looped to the anode for hydrogen oxidation reaction. Theoretical calculations indicate an impressively low energy requirement ranging from 0.07 to 0.53 kWh/kg NaOH for established pH differences of 1.7 to 13.4. Experimentally, we achieved the alkalization with an energy consumption of 0.63 kWh/kg NaOH, which is only 38% of the theoretical energy requirements of the chlor-alkali process (1.64 kWh/kg NaOH). Further tests demonstrated the system’s potential of enduring high current densities (~20 mA/cm 2 ) and operating stability over an extended period (>110 h), showing its potential for future applications. Notably, the CO 2 adsorption tests performed with alkalized seawater exhibited remarkably improved CO 2 capture dictated by the production of hydroxide compared to the pristine seawater.

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

The striking influence of oxophilicity differences in heterometallic Mo–Mn oxide cluster reactions with water

Mixed-metal oxides have proven to be effective catalysts for the hydrogen evolution reaction, often outperforming either of the binary metal oxides. The reactivity of Mn x MoO y - (x = 1, 2; y = 3, 4) clusters toward H 2 O was investigated via time-of-flight mass spectrometry with clear evidence of cluster oxidation and corresponding H 2 production, specifically for Mn x MoO 3 - (x = 1, 2) clusters. Unlike previously studied MoxOy- clusters, which assumed a broad distribution of stoichiometries (typically x ≤ y ≤ 3x), both MnMoOy- and Mn 2 MoO y - preferentially formed y = 3 and 4 compositions in significant quantities under our source conditions. The electronic and molecular structures of the Mn x MoO y (x = 1, 2; y = 3, 4) anion and neutral clusters were probed with anion photoelectron spectroscopy and analyzed with supporting density functional theory calculations. Our studies suggest that both metal centers are involved in initial cluster–water complex formation, while Mo is the center that undergoes oxidation; hence, reactivity terminates when Mo is saturated in its highest oxidation state of +6. Across these four clusters, Mn remains relatively reduced and is stable in a high-spin electronic configuration. The preferential reactivity of water molecules toward the Mo center rather than Mn is rationalized by the much lower relative oxophilicity of Mn.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Hierarchically Porous Multimetal‐Based Carbon Nanorod Hybrid as an Efficient Oxygen Catalyst for Rechargeable Zinc–Air Batteries

Abstract The lack of efficient strategies to address the intrinsic activity, site accessibility, and structural stability issues of metal‐carbon hybrid catalysts is restricting their real‐world implementation on the basis of rechargeable zinc–air batteries. Herein, a dual metal–organic frameworks (MOFs) pyrolysis strategy is developed to regulate the intrinsic activity and porous structure of the derived catalysts, where a Fe 2 Ni_MIL‐88@ZnCo_zeolitic imidazolate framework (ZIF), with a hierarchically porous structure, multifunctional components, and an integrated architecture, acts as an ideal precursor to obtain multimetal based porous nanorod (FeNiCo@NC‐P). Benefitting from the synergetic effect of the multimetal components, facilitated reactant accessibility, and the well‐retained integrated structure, the resultant FeNiCo@NC‐P catalyst exhibits an oxygen reduction reaction half‐wave potential of 0.84 V as well as an oxygen evolution reaction potential of 1.54 V at 10 mA cm –2 . Furthermore, the practical application of FeNiCo@NC‐P in the zinc–air battery displays a low voltage gap and long‐term durability (over 130 h at a current density of 10 mA cm –2 ), which outperforms the commercial noble metal benchmarks. This work not only affords a competitive bifunctional oxygen electrocatalyst for zinc–air batteries but also paves a new way to design and fabricate MOF‐derived materials with tunable catalytic properties.

Ren, Dezhang↗
DOE OSTI2025

Machine learning informed rational design of high entropy double perovskite oxide universal air/steam electrodes for solid oxide electrochemical cells

Due to their high efficiency and versatility, solid oxide electrochemical cells (SOCs) are poised to play a significant role in future energy conversion and storage applications. In recent years, SOCs have bifurcated into two distinct categories: traditional oxygen-ion conducting SOCs that typically operate from ∼650—850 °C and the more recent proton-conducting ceramic (PCC) SOCs that typically operate from ∼400—650 °C. Current performance and lifetime of both oxygen-ion conducting SOCs and PCCs is primarily limited by the air/steam electrode, which facilitates the oxygen reduction reaction (ORR) during fuel cell operation and must also facilitate the oxygen evolution reaction (OER) during electrolysis operation. Here, we present a newly designed high-entropy double perovskite oxide suitable as a universal ORR/OER electrode for both oxygen-ion conducting SOCs and PCCs. Machine learning methods are applied to identify chemical descriptors for highly catalytic high-entropy double perovskite oxides (AA’B 2 O 6 ) across a large compositional space. Based on the machine-learning guidance, we ultimately converge on Ba 0.9 Cs 0.1 (Ca 0.2 Gd 0.2 La 0.2 Pr 0.2 Sr 0.2 )Co 1.5 Fe 0.5 O 6 (CsBaHEO) as a universal air/steam electrode. Structure stabilization is accomplished by an equimolar five-cation high-entropy composition on the A’-site, while cesium substitution on the A-site enhances the electrical conductivity and leads to a higher oxygen vacancy concentration. This material exhibits versatility and high performance in reversible oxygen-ion SOCs, reversible PCCs, and also large-scale tubular PCCs. For example, the CsBaHEO-based PCC reaches 1018 mW∙cm −2 at 600°C, while a large-scale tubular PCC using CsBaHEO for electrolysis achieves a hydrogen production rate of 21.314 ML∙min −1 at 600 °C.

Cell↗
DOE OSTI2021

3d-Orbital Occupancy Regulated Ir-Co Atomic Pair Toward Superior Bifunctional Oxygen Electrocatalysis

Atomically dispersed metal catalysts are hailed as the most promising catalyst category for oxygen electrocatalysis. However, the challenges in regulating electronic configuration and unveiling the mechanism on the atomic scale are hindering their practical implementation. Herein, we modulate the Co d-orbital electron configuration by constructing the Ir–Co atomic pair toward boosted bifunctional activity. The as-developed dual-atom IrCo–N–C catalyst displays unprecedented activity with a half-wave potential of 0.911 V for oxygen reduction reaction and only 330 mV overpotential at 10 mA cm –2 for oxygen evolution reaction, outperforming the single-atom counterparts as well as the commercial Pt/C and Ir/C benchmarks. The impressive bifunctionality is also verified in a Zn–air battery prototype with an ultra-high cyclability over 450 cycles. Furthermore, theoretical calculations are performed to shed light on the synergetic effects of the atomic pair site, where the incorporation of Ir atom alters the d-orbital energy level of Co and thus induces the re-arrangement of d-electron toward intensified spin polarization. As a result, the lower occupancy of d z 2 orbital facilitates the electron acceptation from oxygen to form a stronger Co–O σ bond, thereby propelling faster reaction kinetics.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1976

The possible role of solid surface area in condensation reactions during chemical evolution - Reevaluation

Using surface concentration and reaction rate as the main criteria for the feasibility of condensation reactions, four types of prebiotic environments were analyzed: (1) an ocean-sediment system, (2) a dehydrated lagoon bed produced by evaporation, (3) the surface of a frozen sediment, and (4) a fluctuating system where hydration (rainstorms, tidal variations, flooding) and dehydration (evaporation) take place in a cyclic manner. With the possible exception of nucleotides, low adsorption of organomonomers on sediment surfaces of a prebiotic ocean (pH 8) is expected, and significant condensation is considered unlikely. In dehydrated and frozen systems, high surface concentrations are probable and condensation is more likely. In fluctuating environments, condensation rates will be enhanced and the size distribution of the oligomers formed during dehydration may be influenced by a 'redistribution mechanism' in which adsorbed oligomers and monomers are desorbed and redistributed on the solid surface during the next hydration-dehydration cycle.

Lahav, N.↗
DOE OSTI2020

Anodic electrocatalytic conversion of carboxylic acids on thin films of RuO 2 , IrO 2 , and Pt

The electrocatalytic upgrading of carboxylic acids, abundant biomass-derived molecules, remains a challenging task. In this paper, we report an electrocatalytic decarboxylation (ECDX) approach for the conversion of carboxylic acids into paraffins, olefins, and alcohols via (non-)Kolbe electrolysis on thin films (TFs). The ECDX rate, product selectivity, and current efficiency were potential and electrode dependent. For example, the ECDX activity of RuO 2 -TF was similar to that of Pt foil, but the selectivity to Kolbe products was lower on the former. RuO 2 -TF showed about five times higher rates for the oxygen evolution reaction than Pt foil, which resulted in lower current efficiency. The ECDX and O 2 evolution activities of IrO 2 -TF were potential dependent, but this electrode was selective to non-Kolbe products with low current efficiency (<10 %). This work highlights the performance of thin films as an alternative to bulk metals as anodes for oxidative upgrading of carboxylic acids.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Metal-ligand catalysts for selective promotion of electrochemical CO 2 RR

The electrochemical carbon dioxide reduction reaction (CO 2 RR) provides opportunities to synthesize value-added products from this greenhouse gas in a sustainable manner. Efficient catalysts for this reaction are provided that selectively drive CO 2 reduction over the thermodynamic and kinetically competitive hydrogen evolution reaction (HER) in organic or aqueous electrolytes. The catalysts are metal-polypyridyl coordination complexes of a redox non-innocent terpyridine-based pentapyridine ligand and a first-row transition metal. The metal-ligand cooperativity in [Fe(tpyPY2Me)]2+ drives the electrochemical reduction of CO 2 to CO at low overpotentials with high selectivity for CO 2 RR (>90%).

Derrick, Jeffrey S.↗
DOE OSTI2020

Modified atomic layer deposition of MoS 2 thin films

As one of the most attractive transition metal dichalcogenides (TMDs), the growth of molybdenum disulfide (MoS 2 ) with industrial compatibility is of great importance. Atomic layer deposition (ALD) has been shown to be a promising method to achieve the growth of high-quality TMD materials. However, MoS 2 films deposited by ALD often are amorphous with nonideal stoichiometry and require high-temperature post-deposition annealing. Here, we introduce a modified ALD recipe using Mo(CO) 6 and H 2 S, resulting in controllable linear growth behavior, a S-to-Mo ratio of 2:1, and crystalline films at a temperature as low as 190 °C. The growth mechanisms and key factors leading to this improvement are proposed and complemented by kinetics calculations. This newly developed methodology relies on aligning the process time with the reaction kinetics of carbonyl disassociation. The MoS 2 films prepared herein were shown to be active hydrogen evolution reaction catalysts.

2D materials↗
DOE OSTI2020

From Sodium–Oxygen to Sodium–Air Battery: Enabled by Sodium Peroxide Dihydrate

Metal-air batteries have attracted extensive research interests due to their high theoretical energy density. However, most of the previous studies were limited by applying pure oxygen in the cathode, sacrificing the gravimetric and volumetric energy density. Here, we develop a real sodium-"air" battery, in which the rechargeability of the battery relies on the reversible reaction of the formation of sodium peroxide dihydrate (Na 2 O 2 ∙ 2H 2 O). After an oxygen evolution reaction catalyst is applied, the charge overpotential is largely reduced to achieve a high energy efficiency. The sodium-air batteries deliver high areal capacity of 4.2 mAh.cm -2 and have a decent cycle life of 100 cycles. The oxygen crossover effect is largely suppressed by replacing the oxygen with air, whereas the dense solid electrolyte interphase formed on the sodium anode further prolongs the cycle life.

25 ENERGY STORAGE↗
DOE OSTI2026

Spin‐Polarized Interfaces Redirect CO 2 Reduction From CO to Formate

Achieving high product selectivity in electrocatalytic carbon dioxide reduction (CO 2 RR) remains a critical challenge due to competition between multiple proton-coupled electron-transfer pathways on catalyst surfaces. Meanwhile, chirality-induced spin selectivity (CISS), which enables spin-polarized electron transport through chiral interfaces, has recently emerged as a promising strategy to modulate interfacial electrochemical reactions. Although the CISS effect has been shown to enhance selectivity and efficiency in the spin-sensitive oxygen evolution reaction (OER), its role in regulating CO 2 RR pathways and in stabilizing intermediates remains largely unexplored. Here, chiral molecules (R- and S-1,1′-bi-2-naphthyl-2,2′-diyl hydrogen phosphate, BNP) were integrated with SnO 2 to construct chiral-modified catalysts (R-BNP/SnO 2 and S-BNP/SnO 2 ). Compared with bare SnO 2 and racemic BNP-modified SnO 2 (Rac-BNP/SnO 2 ), the chiral catalysts exhibited a pronounced shift in product selectivity from CO toward formate production. Importantly, in-situ attenuated total reflectance surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) reveals that the chiral interface selectively stabilizes the O-bound *OCHO intermediate associated with the formate pathway and modulates interfacial water structure and hydrogen-bonding dynamics. These findings demonstrate that spin-polarized interfacial electron transfer can regulate CO 2 RR pathway selectivity by modulating the stabilization of key intermediates. More broadly, this work establishes chiral spin-selective interfaces as a new strategy for regulating competitive electrocatalytic reaction pathways.

14 SOLAR ENERGY↗
DOE OSTI2021

Amorphization mechanism of SrIrO 3 electrocatalyst: How oxygen redox initiates ionic diffusion and structural reorganization

The use of renewable electricity to prepare materials and fuels from abundant molecules offers a tantalizing opportunity to address concerns over energy and materials sustainability. The oxygen evolution reaction (OER) is integral to nearly all material and fuel electrosyntheses. However, very little is known about the structural evolution of the OER electrocatalyst, especially the amorphous layer that forms from the crystalline structure. Here, we investigate the interfacial transformation of the SrIrO 3 OER electrocatalyst. The SrIrO 3 amorphization is initiated by the lattice oxygen redox, a step that allows Sr 2+ to diffuse and O 2− to reorganize the SrIrO 3 structure. This activation turns SrIrO 3 into a highly disordered Ir octahedral network with Ir square-planar motif. The final Sr y IrO x exhibits a greater degree of disorder than IrO x made from other processing methods. Our results demonstrate that the structural reorganization facilitated by coupled ionic diffusions is essential to the disordered structure of the SrIrO 3 electrocatalyst.

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

Mapping the Binary Covalent Alloy Space to Pursue Superior Nitrogen Reduction Reaction Catalysts

The electrochemical nitrogen reduction reaction (NRR) has the potential to decarbonize industrial ammonia production. However, NRR has poor activity and selectivity versus the competing hydrogen evolution reaction for catalysts that adhere to scaling relations. Overcoming the limitations imposed by scaling relations requires more complex catalyst materials, however, evaluating materials beyond simple metal systems is a large combinatorial problem that requires an improved understanding of the electrocatalyst surface to rationally guide the discovery of superior catalysts. The study uses grand canonical density functional theory to uncover NRR trends on a large and disparate set of binary covalent alloys (BCA) with variable compositions and active-site geometries. The studied BCAs generally follow scaling relations, albeit with larger variance and several systems that significantly break scaling. BCAs with early- to mid-transition metals tend to lie near the volcano peak and activate the N 2 triple bond via a side-on binding configuration. Trends in the BCA space cannot be readily predicted using simple electronic descriptors, which is ascribed to the large geometric variability of the BCA surfaces. Furthermore, it is anticipated that these findings will provide a foundation for the rational design of superior NRR electrocatalysts with increasing material complexity.

36 MATERIALS SCIENCE↗
DOE OSTI2020

The electrolyte comprising more robust water and superhalides transforms Zn-metal anode reversibly and dendrite-free

A great challenge for all aqueous batteries, including Zn-metal batteries, is the parasitic hydrogen evolution reaction on the low-potential anode. Herein, we report the formula of a highly concentrated aqueous electrolyte that mitigates hydrogen evolution by transforming water molecules more inert. The electrolyte comprises primarily ZnCl 2 and LiCl as an additive, both of which are inexpensive salts. The O–H covalent bonds in water get strengthened in a chemical environment that has fewer hydrogen bonding interactions and a greater number of Zn–Cl superhalides, as suggested by integrated characterization and simulation. As a result, the average Coulombic efficiency of zinc-metal anode is raised to an unprecedented >99.7% at 1 mA cm –2 . In the new electrolyte, the plating/stripping processes leave the zinc-metal anode dendrite-free, and the zinc-metal anode delivers stable plating/stripping cycles for 4000 hours with an areal capacity of 4 mAh cm –2 at 2 mA cm –2 . Furthermore, the high Coulombic efficiency of zinc-metal anode in the ZnCl 2 -LiCl mixture electrolyte is demonstrated in full cells with a limited anode. The V 2 O 5 ·H 2 O| |Zn full cell with an N/P mass ratio of 1.2 delivers a stable life of more than 2500 cycles, and the LiMn 2 O 4 | |Zn hybrid cell with an N/P mass ratio of 0.6 exhibits 1500 cycles in its stable life.

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

Metal–Ligand Cooperativity via Exchange Coupling Promotes Iron- Catalyzed Electrochemical CO 2 Reduction at Low Overpotentials

Biological and heterogeneous catalysts for the electrochemical CO 2 reduction reaction (CO 2 RR) often exhibit a high degree of electronic delocalization that serves to minimize overpotential and maximize selectivity over the hydrogen evolution reaction (HER). Here, we report a molecular iron(II) system that captures this design concept in a homogeneous setting through the use of a redox non-innocent terpyridine-based pentapyridine ligand (tpyPY2Me). As a result of strong metal-ligand exchange coupling between the Fe(II) center and ligand, [Fe(tpyPY2Me)] 2+ exhibits redox behavior at potentials 640 mV more positive than the isostructural [Zn(tpyPY2Me)] 2+ analog containing the redox-inactive Zn(II) ion. This shift in redox potential is attributed to the requirement for both an open-shell metal ion and a redox non-innocent ligand. The metal-ligand cooperativity in [Fe(tpyPY2Me)] 2+ drives the electrochemical reduction of CO 2 to CO at low overpotentials with high selectivity for CO 2 RR (>90%) and turnover frequencies of 100,000 s -1 with no degradation over 20 h. The decrease in the thermodynamic barrier engendered by this coupling also enables homogeneous CO 2 reduction catalysis in water without compromising selectivity or rates. Synthesis of the two-electron reduction product, [Fe(tpyPY2Me)] o , and characterization by X-ray crystallography, Mössbauer spectroscopy, X-ray absorption spectroscopy (XAS), variable temperature NMR, and density functional theory (DFT) calculations, support assignment of an open-shell singlet electronic structure that maintains a formal Fe(II) oxidation state with a doubly reduced ligand system. Furthermore, this work provides a starting point for the design of systems that exploit metal-ligand cooperativity for electrocatalysis where the electrochemical potential of redox non-innocent ligands can be tuned through secondary metal-dependent interactions.

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

Phase segregation reversibility in mixed-metal hydroxide water oxidation catalysts

Achieving stable, low-cost electrocatalysts represents a daunting challenge towards practical water oxidation reactions. Here, we report that a degraded electrocatalyst can be revivified under catalytic operating conditions by manipulating reversible phase segregation. Under the oxygen evolution reaction conditions, Fe segregation develops in the Ni–Fe hydroxide host lat- tice, with the formation of FeOOH, resulting in an interface between the FeOOH and the host lattice. A dynamic metal dissolu- tion–redeposition process accelerates the Fe segregation and formation of the FeOOH secondary phase, resulting in catalyst deactivation. Operando synchrotron spectroscopic and microscopic analyses suggest that the phase segregation is revers- ible between the water oxidation potential and the catalyst reduction potential. Therefore, we have developed an intermittent reduction methodology to revivify the catalytic activity under the operating conditions, enhancing catalyst durability. The pres- ent study highlights that tailoring phase segregation at the catalyst/electrolyte interface constitutes an important strategy for revivifying and stabilizing catalytic activity.

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

Enabling Efficient Water Splitting with Advanced Materials Designed for High pH Membrane Interface

This project was focused on developing the durable, high-performance materials and interfaces for advanced water splitting, enabling a clear pathway for achieving <$2/Kg H2 (on scale) with efficiency of 43 kWh/kg H 2 via anion exchange membrane (AEM)-based electrolysis. We aimed to advance these final goals via an improved fundamental understanding of both hydrogen and oxygen evolution reactions (HER/OER) leading to novel platinum group metal (PGM)-free catalyst materials in conjunction with critical improvements in membrane and ionomers and gas evolution electrodes with corresponding characterization and testing. Northeastern University (NU) lead this effort focusing on catalyst development and characterization (both in situ and ex situ) while project partners lead improvements in ionomer and membrane materials and will aid in the development of specialized electrode and membrane electrode assemblies. In addition, close collaboration occured with the HydroGEN Energy Materials Network (EMN) National Laboratory consortium including efforts related to use of advanced ionomers, durability protocols and validation of electrolyzer materials (e.g. NREL), multiscale modeling and computation (e.g. LBNL), and molecular dynamics (MD) simulations of the membrane catalyst interface (e.g. SNL). The interactions with HydroGEN included exchange of data and materials as needed to facilitate project success.

08 HYDROGEN↗
DOE OSTI2022

Reaction mechanism and kinetics for N 2 reduction to ammonia on the Fe–Ru based dual-atom catalyst

Environmental and energy considerations demand that the Haber-Bosch process for reducing N 2 to NH 3 be replaced with electrochemical ammonia synthesis where the H atoms come from water instead of from H 2 . But a practical realization of electrochemical N 2 reduction reaction (NRR) requires the development of new generation electrocatalysts with low overpotential and high Faraday efficiency (FE). A major problem here is that the hydrogen evolution reaction (HER) competes with NRR. Herein, we consider new generation dual-site catalysts involving two different metals incorporated into a novel two-dimensional C 3 N–C 2 N heterostructure that provides a high concentration of well-defined but isolated active sites that bind two distinct metal atoms in a framework that facilitates electron transfer. We report here the mechanism and predicted kinetics as a function of applied potential for both NRR and HER for the (Fe–Ru)/C 3 N–C 2 N dual atom catalyst. These calculations employ the grand canonical potential kinetics (GCP-K) methodology to predict reaction free energies and reaction barriers as a function of applied potential. The rates are then used in a microkinetic model to predict the turn-over-frequencies (TOF) as a function of applied potential. At U = 0 V, the FE for NRR is 93%, but the current is only 2.0 mA cm –2 . The onset potential (at 10 mA cm –2 ) for ammonia on Fe–Ru/C 3 N–C 2 N is –0.22 V RHE . This leads to a calculated TOF of 434 h –1 per Fe–Ru site. In conclusion, we expect that the mechanisms for NRR and HER developed here will help lead to new generations of NRR with high TOF and FE.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗