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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 685 records · Page 38
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

On the mechanisms of ion adsorption to aqueous interfaces: air-water vs. oil-water

The adsorption of ions to water-hydrophobe interfaces influences a wide range of phenomena, including chemical reaction rates, ion transport across biological membranes, and electrochemical and many catalytic processes; hence, developing a detailed understanding of the behavior of ions at water-hydrophobe interfaces is of central interest. Here, we characterize the adsorption of the chaotropic thiocyanate anion (SCN − ) to two prototypical liquid hydrophobic surfaces, water-toluene and water-decane, by surface-sensitive nonlinear spectroscopy and compare the results against our previous studies of SCN − adsorption to the air-water interface. For these systems, we observe no spectral shift in the charge transfer to solvent spectrum of SCN − , and the Gibb’s free energies of adsorption for these three different interfaces all agree within error. We employed molecular dynamics simulations to develop a molecular-level understanding of the adsorption mechanism and found that the adsorption for SCN − to both water-toluene and water-decane interfaces is driven by an increase in entropy, with very little enthalpic contribution. This is a qualitatively different mechanism than reported for SCN − adsorption to the air-water and graphene-water interfaces, wherein a favorable enthalpy change was the main driving force, against an unfavorable entropy change.

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

Anodic Interfacial Evolution in Extremely Fast Charged Lithium-Ion Batteries

Interfacial reaction mechanisms at the anode/separator interface play a central role in the performance and safety of lithium-ion batteries during fast charging. We report a mechanistic study on the evolution and interactions of the aging mechanisms at the anode/separator interface in lithium cobalt oxide/graphite pouch cells charged with variable charging rates (1–6C) over 10 cycles. In situ electrochemical measurements, including voltage relaxation, Coulombic efficiency, and direct current internal resistance, indicated an incremental lithium loss until the C rates were ≤5C. A substantial capacity fade is observed in the first few cycles of fast charging, but the magnitude of capacity fade progressively diminishes with the number of cycles, indicating a suppression in the lithium deposition mechanism. Post-mortem film thickness, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) analyses were performed to elucidate the evolution of electrolyte decomposition, the solid–electrolyte interface (SEI), lithium plating, and film fracture mechanisms with C rate. XPS measurements confirmed an increasing lithium concentration in an SEI film with an increase in the C rate. SEM images showed a growth of dendritic lithium on the anode surface from 1C to 3C. Precrack formation leading to an interfacial film fracture was observed at higher C rates. Furthermore, a differential analysis of the discharge capacity indicated a possible two-phase delithiation from the anode and reduced cathodic lithiation due to lithium loss at high C rates.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Size-Dependent Adsorption and Adhesion Energetics of Ag Nanoparticles on Graphene Films on Ni(111) by Calorimetry

Interest in the use of carbon supports for late transition metal nanoparticle catalysts has expanded rapidly due to the increasing importance of electrocatalysts for clean energy and environmental technologies and the use and storage of renewable electricity. Compared to oxide supports, almost nothing is known about the effect of metal nanoparticle size on the energies of the metal atoms within carbon-supported nanoparticles, yet these energies are crucial for understanding their surface reactivity and sintering kinetics. Here, the growth morphology and adsorption energetics of vapor-deposited Ag onto clean graphene/Ni(111) surfaces have been studied using a combination of single-crystal adsorption calorimetry (SCAC) and He + low-energy ion scattering (LEIS). The differential heat of Ag adsorption is 207 kJ/mol for making ~30 atom Ag particles on graphene terraces at 100 K and 16 kJ/mol higher for making ~9 atom Ag clusters at defect sites at the same temperature. The heat of adsorption increases rapidly with Ag coverage as 3D Ag nanoparticles nucleate and grow in size, asymptotically reaching within 5 kJ/mol of the bulk Ag sublimation enthalpy (285 kJ/mol) by 2 ML. The heats of adsorption and Ag nanoparticle densities from LEIS (~10 16 /m 2 ) were combined to provide the Ag/graphene adhesion energy (E adh = 1.8 J/m 2 in the large-particle limit) and the Ag chemical potential (μ) versus effective particle diameter (D). The Ag chemical potential was well-fitted by μ(D) = (3γ v /M – E adh )(1 + (1.5 nm)/D)(2V m /D), where γ v /M is the surface energy of bulk Ag and V m is its molar volume. The same equation is known to fit similar data for late transition metals on clean surfaces of metal oxide single crystals. The adhesion energy of Ag measured here on graphene falls within the wide range measured for Ag on those oxide surfaces and is almost as large as on the oxide that binds Ag particles most strongly, namely CeO 2 (111), which is well-known to be very effective at resisting catalyst deactivation by metal sintering. Furthermore, these results imply that carbon supports will be effective at resisting sintering and that Ag particles smaller than 6 nm on graphene will bind small adsorbed reaction intermediates more weakly than supports with weaker adhesion to Ag, like MgO(100).

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

Highly efficient Pt catalyst on newly designed CeO 2 -ZrO 2 -Al 2 O 3 support for catalytic removal of pollutants from vehicle exhaust

Pt-CeO 2 catalysts have been widely studied for the vehicle emission control. Designing novel CeO 2 based supports with improved physical-chemical properties has become a research hotspot to further promote the catalytic performance and stability of Pt-CeO 2 catalysts. In this work, through utilizing a unique, two-step incipient wetness impregnation (T-IWI) method for ceria-zirconia-alumina (CZA-T) support preparation, a Pt single site catalyst (Pt/CZA-T) with excellent thermal stability was synthesized. Higher oxidation activity and Oxygen storage capacity (OSC) were achieved on activated Pt/CZA-T, comparing to Pt catalysts on regular CeO 2 /Al 2 O 3 (Pt/CA) and one-step prepared CeZrO x /Al 2 O 3 (Pt/CZA). Via the modification of hydrophilic/hydrophobic properties of γ-Al 2 O 3 by this unique T-IWI method, finer Ce 0.9 Zr 0.1 O 2 particles with higher density of surface defects were formed on CZA-T, on which a higher Pt dispersion and stronger Pt-O-Ce interaction were achieved. Upon activation, smaller, well-dispersed Pt clusters on CZA-T were generated. It was concluded that the CO oxidation performance and OSC were highly related to the size of Pt clusters on different supports that we have developed. Finally, more Pt sites located at Pt cluster-CeZrO x interfaces, which were the real active sites, were responsible for the highest OSC function and CO oxidation activity of activated Pt/CZA-T catalyst.

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

Structural and Dynamical Roles of Bound Polymer Chains in Rubber Reinforcement

The addition of nanofillers to rubber matrices is a powerful route to improve the mechanical properties. Here, we focus on a molecular understanding of basic mechanisms that are important for the reinforcement in rubbers. The key role in this process is ascribed to bound rubber (BR) that engages with the matrix as well as with adjacent nanofillers. To date, this understanding has been impeded by the lack of experimental tools to directly probe the BR chains buried in a polymer matrix composed of the same polymer. To tackle this challenge, we combine neutron scattering/spectroscopy techniques with isotope-labeling and molecular dynamics simulations. The system is a simplified carbon-black-filled polybutadiene. The combined experimental and computational results provide new insights into the local structural and dynamical heterogeneities of BR chains and their interactions with the matrix polymer, highlighting (i) the structural partition of the bound chains into three components (i.e., trains, loops, and tails) and their fractions; (ii) their dynamical hierarchies, i.e., the trains that remain immobile on the filler surface, the loops that are fairly large and hence allow the interdigitation of matrix chains, and the tails with their unique characteristics to reach far out into the matrix and entangle with matrix chains. These multiple roles of the constituent components of the BR chains promote the formation of a well-developed adhesive polymer–filler interface, enhancing the elastic property of a filled rubber. Finally, the comprehensive understanding derived and validated by the model rubber will be translatable to many other polymer nanocomposites.

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

The Influence of Nonlocal Metal–Dielectric Environments on Physical and Chemical Processes

Plasmonic nanolayers and laminar metallic/dielectric multilayers were originally developed for optical cloaking applications and lensing applications that could potentially image objects whose size was below the diffraction limit. These assemblies were initially formed from gold or silver nanorods grown within an alumina mesh. However, more recently, assemblies with similar properties have also been prepared by sequential thin-layer deposition of alternating layers of gold and magnesium fluoride (MgF 2 ). These metal/dielectric composite materials enable control of the dielectric constant in the directions perpendicular to the layers and balance the real and imaginary dielectric constants of the assembly such that the speed and the amplitude of the waves traveling through the assembly are not attenuated. In this Account, we will also focus on a few of the applications ranging from surface wetting to fluorescence quenching to enhancement of photochemical reactions. First, we will share an introduction to processes used to create these materials, which are combinations of low refractive index metals and transparent higher index materials arranged in a scalable repeating fashion. Two fabrication methods were employed: an electrochemical deposition of Ag nanorods into an anodized alumina matrix which produced materials with an anisotropic negative refractive index material within the plane of the film and lamellar metal/dielectric layers in which the negative index perpendicular to the growth direction. These alternating layers of plasmonic metals and dielectric materials were ultimately chosen to prepare films for further testing, because of their relative ease of fabrication. We will continue with a discussion of a few of the applications of both of these nonlocal dielectric composite materials including more specialized plasmonic, composite, and hyperbolic metamaterials including fluorescence quenching, photochemical reactions, and surface wetting. In each of these applications, the unique response caused by the enhancement of the electric field and the interface between hyperbolic materials and plasmonic materials as they interact photophysically with their near neighbors is presented. In each of the applications, the enhanced electric field extends from the composite substrate layer to interact with its near neighbors and beyond. Furthermore, the presence of this extended interaction can be observed in the form of decreased emission lifetime, enhancement of photochemical reaction rates, and changes in the surface energies measured by contact angle goniometry. In this Account, all of these situations will be addressed. Finally, we will conclude with a summary and vision for the future as well as a discussion of the unique challenges and opportunities available as research active faculty at an HBCU.

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

Steering the Methane Dry Reforming Reactivity of Ni/La 2 O 3 Catalysts by Controlled In Situ Decomposition of Doped La 2 NiO 4 Precursor Structures

The influence of A- and/or B-site doping of Ruddlesden-Popper perovskite materials on the crystal structure, stability, and dry reforming of methane (DRM) reactivity of specific A 2 BO 4 phases (A = La, Ba; B = Cu, Ni) has been evaluated by a combination of catalytic experiments, in situ X-ray diffraction, X-ray absorption spectroscopy (XAS), X-ray photoelectron spectroscopy (XPS), and aberration-corrected electron microscopy. At room temperature, B-site doping of La 2 NiO 4 with Cu stabilizes the orthorhombic structure ( Fmmm ) of the perovskite, while A-site doping with Ba yields a tetragonal space group ( I 4/ mmm ). We observed the orthorhombic-to-tetragonal transformation above 170 °C for La 2 Ni 0.9 Cu 0.1 O 4 and La 2 Ni 0.8 Cu 0.2 O 4 , slightly higher than for undoped La 2 NiO 4 . Loss of oxygen in interstitial sites of the tetragonal structure causes further structure transformations for all samples before decomposition in the temperature range of 400 °C-600 °C. Controlled in situ decomposition of the parent or A/B-site doped perovskite structures in a DRM mixture (CH 4 :CO 2 = 1:1) in all cases yields an active phase consisting of exsolved nanocrystalline metallic Ni particles in contact with hexagonal La 2 O 3 and a mixture of (oxy)carbonate phases (hexagonal and monoclinic La 2 O 2 CO 3 , BaCO 3 ). Differences in the catalytic activity evolve because of (i) the in situ formation of Ni-Cu alloy phases (in a composition of >7:1 = Ni:Cu) for La 2 Ni 0.9 Cu 0.1 O 4 , La 2 Ni 0.8 Cu 0.2 O 4 , and La 1.8 Ba 0.2 Ni 0.9 Cu 0.1 O 4 , (ii) the resulting Ni particle size and amount of exsolved Ni, and (iii) the inherently different reactivity of the present (oxy)carbonate species. Based on the onset temperature of catalytic DRM activity, the latter decreases in the order of La 2 Ni 0.9 Cu 0.1 O 4 ~ La 2 Ni 0.8 Cu 0.2 O 4 ≥ La 1.8 Ba 0.2 Ni 0.9 Cu 0.1 O 4 > La 2 NiO 4 > La 1.8 Ba 0.2 NiO 4 . Simple A-site doped La 1.8 Ba 0.2 NiO 4 is essentially DRM inactive. The Ni particle size can be efficiently influenced by introducing Ba into the A site of the respective Ruddlesden-Popper structures, allowing us to control the Ni particle size between 10 nm and 30 nm both for simple B-site and A-site doped structures. Hence, it is possible to steer both the extent of the metal-oxide-(oxy)carbonate interface and its chemical composition and reactivity. Counteracting the limitation of the larger Ni particle size, the activity can, however, be improved by additional Cu-doping on the B-site, enhancing the carbon reactivity. Exemplified for the La 2 NiO 4 based systems, we show how the delicate antagonistic balance of doping with Cu (rendering the La 2 NiO 4 structure less stable and suppressing coking by efficiently removing surface carbon) and Ba (rendering the La 2 NiO 4 structure more stable and forming unreactive surface or interfacial carbonates) can be used to tailor prospective DRM-active catalysts.

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

Reversible electrowetting transitions on superhydrophobic surfaces

An electric field applied across the interface has been shown to enable transitions from the Cassie to the Wenzel state on superhydrophobic surfaces with miniature corrugations. Molecular dynamics (MD) simulations manifest the possibility of reversible cycling between the two states when narrow surface wells support spontaneous expulsion of water in the absence of the field. With approximately 1 nm sized wells between the surface asperities, the response times to changes in the electric field are of O(0.1) ns, allowing up to GHz frequency of the cycle. Because of the orientation preferences of interfacial water in contact with the solid, the phenomenon depends on the polarity of the field normal to the interface. The threshold field strength for the Cassie-to-Wenzel transition is significantly lower for the field pointing from the aqueous phase to the surface; however, once in the Wenzel state, the opposite field direction secures tighter filling of the wells. Considerable hysteresis revealed by the delayed water retraction at decreasing field strength indicates the presence of moderate kinetic barriers to expulsion. Known to scale approximately with the square of the length scale of the corrugations, these barriers preclude the use of increased corrugation sizes while the reduction of the well diameter necessitates stronger electric fields. Field-controlled Cassie-to-Wenzel transitions are therefore optimized by using superhydrophobic surfaces with nanosized corrugations. Abrupt changes indicate a high degree of cooperativity reflecting the correlations between the wetting states of interconnected wells on the textured surface.

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

Liquid Crystal‐Based Detection of Antigens with ELISA Sensitivity

Abstract A highly sensitive label‐free liquid crystal (LC)‐based technique is presented for detecting Immunoglobulin G (IgG) antigens used to uncover viral infections. The effectiveness, sensitivity, and selectivity of this detection method is demonstrated with goat IgG antigen at concentrations as low as 100 pg ml −1 , which is comparable to the sensitivity of the current enzyme‐linked immunosorbent assay (ELISA). The sensor is fabricated by decorating a transmission electron microscopy grid immobilized glass surfaces with antibodies; the target antigen is detected by a liquid crystal suspended onto the grid. This is different from previous methods where the antigen is detected either at the LC‐aqueous interface or in an LC sandwich cell with an antibody/antigen‐decorated substrate. This new approach has advantages such as easy sample preparation, higher sensitivity, and better storage capabilities. Binding the target antigen to the antibody results in a reorientation of the LC director that is detected optically. In addition to demonstrating the sensitivity, the physical principle of the detection is also discussed. This technique may apply to detect virtually any antigen of interest.

36 MATERIALS SCIENCE↗
DOE OSTI2022

MoO x S y /Ni 3 S 2 Microspheres on Ni Foam as Highly Efficient, Durable Electrocatalysts for Hydrogen Evolution Reaction

Hydrogen energy derived from water splitting is the cleanest renewable energy source, but it is also very challenging to achieve because the hydrogen evolution reaction (HER) requires highly efficient and low-cost electrocatalysts. Here, we have fabricated a novel hierarchical system of amorphous molybdenum oxy/sulfide microspheres with crystalline Ni 3 S 2 intergrown in situ on Ni foam (MoO x S y /Ni 3 S 2 /NF) as an outstanding electrocatalyst for HER. The MoO x S y /Ni 3 S 2 /NF demonstrates an ultra-low overpotential of 58 mV at a current density of 10 mA cm -2 and extremely durable stability (>200 h), suggesting superior performance comparable to that of Pt-C/NF under acidic conditions. The X-ray absorption fine structure (XAFS) determines the average valence state of Mo to be +(5 + δ), with a coordination motif by O and S. To explain such high HER activity, a [Mo 2 O 2 (S,O) 4 ] dimer-based periodic model structure with the average composition of [Mo 4 O 8 S 4 ] interfaced with the Ni 3 S 2 (101) surface is proposed. The interactions between the Ni of Ni 3 S 2 and bridging S/O of [Mo 4 O 8 S 4 ] result in an average formal Mo charge state between +5 and +6, and significant charge transfer from Ni 3 S 2 to [Mo 4 O 8 S 4 ] activates the Mo = O bonds. The calculated |ΔG H* | of less than 50 meV suggests that the double-bonded O is the most active site. This work points to the importance of oxy/sulfides with Mon+ (+5 < n < +6) as exceptional electrochemical catalysts for HER.

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

Core–Shell Covalently Linked Graphitic Carbon Nitride–Melamine–Resorcinol–Formaldehyde Microsphere Polymers for Efficient Photocatalytic CO 2 Reduction to Methanol

Photocatalytic reduction of CO 2 with light and H 2 O to form CH 3 OH is a promising route to mitigate carbon emissions and climate changes. Although semiconducting metal oxides are potential photocatalysts for this reaction, low photon efficiency and leaching of environmental unfriendly, toxic metals limit their applicability. Here, we report a metal-free, core-shell photocatalysts consisting of graphitic carbon nitride (g-C 3 N 4 , CN) covalently linked to melamine-resorcinol-formaldehyde (MRF) microsphere polymers for this reaction. Cova-lent linkage enabled efficient separation of photo-generated carriers and photocatalysis. Using 100 mg of a photocatalyst containing 15 wt.% CN, a CH 3 OH yield of 0.99 μmol·h -1 was achieved at a reaction temperature of 80 °C and 0.5 MPa with external quantum efficiencies ranging from 5.5% at 380 nm to 1.7% at 550 nm. The yield was about 20 and 10 times higher than that of its components CN and MRF, respectively. Characterization with XPS, TEM, and bulk and surface elemental analyses supported a core-shell structure and charge transfer at C-N bond at the CN-MRF interface between the methoxy group in the 2,4-trishydroxylmethyl-1,3-diphenol part of MRF and the terminal amino groups in the CN. This enhanced ligand-to-ligand charge transfer resulted in 67% of photo-excited internal charge transferred from CN to hy-droxymethylamino group in MRF, whose amino group was the catalytic site for CO 2 photocatalytic reduction to CH 3 OH. Furthermore, this study provides a series of new metal-free photocatalyst designs and insights into the molecular-level structure-mediated photocatalytic response

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

Bioadhesive polymer semiconductors and transistors for intimate biointerfaces

The use of bioelectronic devices relies on direct contact with soft biotissues. For transistor-type bioelectronic devices, the semiconductors that need to have direct interfacing with biotissues for effective signal transduction do not adhere well with wet tissues, thereby limiting the stability and conformability at the interface. Here we report a bioadhesive polymer semiconductor through a double-network structure formed by a bioadhesive brush polymer and a redox-active semiconducting polymer. The resulting semiconducting film can form rapid and strong adhesion with wet tissue surfaces together with high charge-carrier mobility of ~1 square centimeter per volt per second, high stretchability, and good biocompatibility. Further fabrication of a fully bioadhesive transistor sensor enabled us to produce high-quality and stable electrophysiological recordings on an isolated rat heart and in vivo rat muscles.

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

Toward alcohol synthesis from CO hydrogenation on Cu(111)-supported MoS 2 – predictions from DFT+KMC

In the quest for cheap and efficient catalysts for alcohol synthesis from syngas, a material of interest is single-layer MoS2 owing to its low cost, abundancy, and flexible structure. Because of the inertness of its basal plane, however, it is essential to find ways that make it catalytically active. Herein, by means of density functional theory based calculations of reaction pathways and activation energy barriers and accompanying kinetic Monte Carlo simulations, we show that while S vacancy row structures activate the MoS 2 basal plane, further enhancement of chemical activity and selectivity can be achieved by interfacing the MoS 2 layer with a metallic support. When defect-laden MoS2 is grown on Cu(111), there is not only an increase in the active region (surface area of active sites) but also charge transfer from Cu to MoS 2 , resulting in a shift of the Fermi level such that the frontier states (d orbitals of the exposed Mo atoms) appear close to it, making the MoS 2 /Cu(111) system ready for catalytic activity. Finally, our calculated thermodynamics of reaction pathways lead to the conclusion that the Cu(111) substrate promotes both methanol and ethanol as the products, while kinetic Monte Carlo simulations suggest a high selectivity toward the formation of ethanol.

2D materials↗
DOE OSTI2024

Synergistic Effects of the Electric Field Induced by Imidazolium Rotation and Hydrogen Bonding in Electrocatalysis of CO 2

The roles of the ionic liquid, 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF₄]), and water in controlling the mechanism, energetics, and electrocatalytic activity of CO₂ reduction to CO on silver in non-aqueous electrolytes were investigated. The first electron transfer occurs to CO₂ at reduced overpotentials when it is trapped between the planes of [EMIM]⁺ ring and electrode surface due to cation re-orientation as determined from voltammetry, in-situ surface-enhanced Raman spectroscopy, and density functional theory calculations. Within this interface, water up to 0.5 M does not induce significant faradaic activity, opposing the notion of it as a free proton source. Instead, water acts as a hydrogen bond donor and the proton is sourced from [EMIM]⁺. Furthermore, this study demonstrates that alcohols with varying acidity tune the hydrogen bonding network in the interfacial microenvironment to lower the energetics required for CO₂ reduction. Here, the hydrogen bonding suppresses the formation of inactive carboxylate species, thus preserving the catalytic activity of [EMIM]⁺. The ability to tune the hydrogen bonding network opens new avenues for advancing IL-mediated electrocatalytic reactions in non-aqueous electrolytes.

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

Enabling stable and high-rate cycling of a Ni-rich layered oxide cathode for lithium-ion batteries by modification with an artificial Li⁺-conducting cathode-electrolyte interphase

Ni-rich LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) cathodes are investigated to realize high energy density Li ion batteries for long life electric vehicle applications. However, capacity decay and thermal instability due to cathode-electrolyte interfacial degradation remain challenges that require sophisticated surface stabilization methods to address. Here, we propose a strategy, for the first time, to form an artificial Li + -conducting cathode-electrolyte interphase (ALCEI) on the NCM811 cathode surface using a nucleophilic reaction between polysulfides and vinylene carbonate (VC). Furthemore, the as-formed ALCEI layer simultaneously protects the NCM particles from electrolyte corrosion and facilitates Li + ion transport, thus enabling stable and high rate cycling of NCM811. As a result, the ALCEI-modified NCM811 cathode exhibits a high capacity (211.6 mA h g -1 at 0.1C), notable rate capability (134 mA h g -1 at 10C), and superior cycle stability (94.2% over 200 cycles at 1C). These results underscore the use of interfacial engineering in high voltage cathode material development and provide a feasible strategy for stabilizing Ni-rich cathode interfaces in practical Li ion battery applications.

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

Atomistic-Scale Simulations on Graphene Bending Near a Copper Surface

Molecular insights into graphene-catalyst surface interactions can provide useful information for the efficient design of copper current collectors with graphitic anode interfaces. As graphene bending can affect the local electron density, it should reflect its local reactivity as well. Using ReaxFF reactive molecular simulations, we have investigated the possible bending of graphene in vacuum and near copper surfaces. We describe the energy cost for graphene bending and the binding energy with hydrogen and copper with two different ReaxFF parameter sets, demonstrating the relevance of using the more recently developed ReaxFF parameter sets for graphene properties. Moreover, the draping angle at copper step edges obtained from our atomistic simulations is in good agreement with the draping angle determined from experimental measurements, thus validating the ReaxFF results.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗