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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 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Ir(hkl) Surface Electrochemistry in a Nonadsorbing Acidic Medium

The fundamental properties of electrochemical materials depend on the multiple and often complex interactions between electrode surface sites and electrolyte species at the electrochemical interface. Despite Iridium use in electrolyzer systems, much of its surface electrochemistry remains underexplored. This study investigates the surface electrochemistry of Ir(111), Ir(100), and Ir(110) surfaces in acidic media. Using cyclic voltammetry and CO charge displacement experiments, we establish the charge states and adsorbate coverages as a function of the electrode potential, revealing the presence of hydrogen and hydroxyl co-adsorption at low potentials on (111), and almost no coverage of H ad on (110) facet. In situ Shell Isolated Nanoparticle Enhanced Raman Spectroscopy experiments provide direct evidence of the formation of key adsorbate species, such as hydrogen, hydroxyl, and oxygen, but most importantly, their interactions with interfacial water, confirmed by Density Functional Theory calculations. Our findings highlight the role of co-adsorption and interspecies interactions, with microkinetic adsorption voltammetry simulations corroborating the influence of lateral interactions on adsorption dynamics, particularly for Ir(100) where the OHad formation occurs as a sharp adsorption/desorption current. Our results underscores the importance of interfacial water and hydrogen bonding networks in shaping the electrochemical behavior on Ir surfaces, refining our baseline understanding of the Ir surface electrochemistry necessary for the development of advanced Ir-based electrochemical materials.

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

Titanium-, Nitrogen-Doped Carbon Flowers Catalyze Electrochemical Nitrate Reduction Reaction to Ammonia

An emerging design heuristic for electrochemical nitrate reduction (NO 3 RR) catalysts is synthesizing electron-deficient sites to facilitate binding of electron-rich NO 3 – . However, this rule has rarely been applied to metal-, nitrogen-doped carbon (MNC) catalysts. Titanium (Ti), with low electronegativity and high NO 3 RR reactivity, is a compelling MNC candidate. To date, atomically dispersed TiN x motifs have eluded synthesis due to the strong oxophilicity of Ti. Here, in this work, we leverage nitrogen-rich carbon flowers (CF) to overcome synthetic challenges and produce Ti-, N-doped carbon flower (TiCF) catalysts. Advanced materials characterization demonstrates that TiCF catalysts are a mixed phase material with 3/4 of Ti atoms in TiO 2 -like nanoparticles and 1/4 of Ti atoms in novel, atomically dispersed TiN x sites. TiCF achieves 61 ± 7% NH 3 -selectivity at −0.70 V vs RHE and 14 ± 5 mA/cm 2 to NH 3 formation (| j NH 3 |) at −0.85 V vs RHE in (0.1 M NaOH + 0.1 M NaNO 3 + 0.45 M Na 2 SO 4 ) electrolyte. Control studies show both CF morphology and Ti sites are essential for high NO 3 RR activity. Density functional theory calculations attribute the NO3RR reactivity to TiN x , which facilitates multiple bond formation with surface intermediates to promote favorable NH3 synthesis pathways. Thus, TiCF exhibits 60× higher | j NH 3 | values than bulk Ti and NH 3 yield rates (>0.06 mmol NH 3 /h/cm 2 ) that are competitive with state-of-the-art MNC catalysts (e.g., FeNC, CuNC). TiCF introduces a new class of Ti electrocatalysts, advancing the MNC design space and sustainable NH 3 production.

ammonia↗
DOE OSTI2025

Systematic Bandgap Engineering of a 2D Organic–Inorganic Chalcogenide Semiconductor via Ligand Modification

Hybrid organic–inorganic semiconductors present new opportunities for optoelectronic materials design not available in all-organic or all-inorganic materials. One example is silver phenylselenide (AgSePh) – or “mithrene” – a blue-emitting 2D organic–inorganic semiconductor exhibiting strong optical and electronic anisotropy. Here, we show that the bandgap of mithrene can be systematically tuned by introducing electron-donating and electron-withdrawing groups to the phenyl ligands. We synthesized nine mithrene variants, eight of which formed 2D van der Waals crystals analogous to those of AgSePh. Density functional theory calculations reveal that these 2D mithrene variants are direct-gap or nearly direct gap semiconductors. Furthermore, we identify correlations between the optical gap and three experimental observables – the Hammett constant, 77 Se chemical shift, and selenium partial charge – offering predictive power for bandgap tuning. These findings highlight new opportunities for applying the tools of chemical synthesis to semiconductor materials design.

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

Electron Transfer Theory Elucidates the Hidden Role Played by Triethylamine and Triethanolamine during Photocatalysis

Triethylamine (TEA) and triethanolamine (TEOA) are renowned, in part, for their ability to reductively quench excited states by outer-sphere electron transfer with vast and still growing applications as sacrificial electron donors for photocatalytic systems. Upon amine oxidation, the resulting TEA •+ and TEOA •+ radical cations undergo proton transfer (or hydrogen atom transfer), resulting in the formation of a chemical reductant that has an α-carbon centered radical adjacent to the nitrogen center (TEA • and TEOA • ). In this contribution, we have electrochemically and spectroscopically characterized a set of electron acceptors which, upon accepting an electron, are a series of photocatalysts, [ReCl(R 1 R 2 -bpy)(CO) 3 ] •– , where R 1 and R 2 are electron-donating and electron-withdrawing groups in the 4,4′- and 5,5′-positions on the bipyridyl ligand. Here, we substantiated the formation of the electron donors, TE(O)A • , by spin trapping electron paramagnetic resonance spectroscopy, where TE(O)A • reacts with 2,4,6-tri-tert-butylnitrosobenzene to generate N-centered and O-centered radical adducts. Having established the chemical behaviors of the electron acceptors and donors individually, the electron transfer rate constants were determined across a 1.43 V range in driving force. The redox potential of TEA • was benchmarked to within ±80 mV on an absolute scale in V vs Fc + /Fc in CH 3 CN by using an empirical rate vs free-energy correlation, electron transfer theory, and density functional theory calculations. The equilibrium potentials for TEA • and TEOA • were determined to be −1.98 V and −1.76 V, respectively. Based on the kinetic and thermochemical analysis presented for TEA • and TEOA • , these transient radicals can be broadly considered strong homogeneous chemical reductants within the wider context of photoredox potentials. Thus, this work clarifies a frequently unnoticed secondary function for these sacrificial electron donors during photocatalysis and rationalizes the possibility of a one-photon/two-electron conversion process that is dependent on the free-energy exchange between TE(O)A • and photocatalysts.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2025

Decoding the Oxygen Activity with Iron through Ligand-to-Metal Charge Transfer in Li-Rich Layered Cathodes

The quest for high-energy-density and cost-effective cathode materials has revitalized lithium-rich iron-based oxides, where Fe 3+ ions with their stable half-filled d 5 electronic configuration demonstrate unique potentials in regulating oxygen redox activity through ligand-to-metal charge transfer. Using operando 57 Fe Mössbauer spectroscopy, synchrotron X-ray techniques, and density functional theory calculations, we unravel the enhanced Fe–O redox activity through the LMCT process and the concomitant evolution of local structure distortion in the Li-rich layered system Li 1.2 MO 2 (M = Ni, Mn, Fe). The metastable Fe 4+ intermediates facilitate early activation of oxygen redox through LMCT along with increased delithiation at a lowered potential (below 4.5 V). Here, this process inherently suppresses Jahn–Teller distortion of Fe 4+ and exhibits Fe–O redox dominance over conventional Fe 3+ /Fe 4+ redox in Li-rich oxides. The Fe–O coupling redox exhibits improved initial Coulombic efficiency and 95% capacity retention over 200 cycles at 4.4 V. However, the LMCT process is accompanied by aggravated cation migration and voltage fade at low cutoff potentials, which requires further mitigation for the utilization of Fe–O redox. Overall, these findings demonstrate the regulating mechanism of iron for oxygen redox through LMCT and provide fundamental insights into the design principles for high-performance, cost-effective iron-based cathode materials.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Chlorocobaltate-Enabled Selective Separation of CoCl 2 from Mixed Chloride and Nitrate Salts of Mn, Co, and Ni

Described here is the effect of anionic metalates─chlorocobaltate and nitratocobaltate─on the heat-driven separation of the critical element cobalt from potentially competing transition metal salts. Resins bearing the hexadentate glycolamide receptor L (PS-L) exhibit sorption capacities, Q = 1.33 mmol/g for CoCl 2 and Q = 0.66 mmol/g for Co(NO 3 ) 2 , as inferred from sorption isotherm studies. This trend runs counter to the typical Hofmeister series for anion selectivity. Ion chromatographic analysis of a mixed CoCl 2 /Co(NO 3 ) 2 solution revealed an increase in chloride content from 55 mol % to 90 mol % after a single thermally driven catch-and-release cycle. This chloride-selective behavior was recapitulated in a mixed-metal cation, mixed-anion system containing the chloride and nitrate salts of Mn(II), Co(II), and Ni(II) at near-equimolar concentrations. PS-L also displayed enhanced selectivity for Co using this mixed stock solution as observed by ICP-OES. In contrast, for a nitrate-only solution containing Mn(II), Co(II), and Ni(II), PS-L showed increased affinity for Mn, with its proportion rising from 36.6 mol % to 58.1% after a single catch-and-release cycle. Density functional theory calculations support the suggestion that the enhanced uptake of Co(II) in chloride-rich media arises from the high thermodynamic stability of [CoCl 4 ] 2– , which facilitates its outer-sphere coordination to cationic resin-bound cobalt species. Single crystal X-ray crystallographic analyzes of L•MCl 2 (M = Mn, Co, Ni) and L•M(NO 3 ) 2 (M = Mn, Co) confirmed metal complexation by L in the solid state and the concomitant formation of metalate counteranions. Here, the present study highlights a relatively simple approach for separating cobalt from its transition metal congeners.

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

Helical Complex Ladder Polymer with Amplification of Asymmetry

Here, we report a Cu–salen helical complex ladder polymer (HLP-Cu) built from covalently fused Cu(Salen) units. Point chirality from enantiopure diamines directs the formation of a rigid, π-conjugated helix. Compared with a planar analogue (LLP-Cu) and the Cu(Salen) monomer, HLP-Cu exhibits up to 5-fold stronger circular dichroism and a maximum dissymmetry factor of 7.4 × 10 –3 . Titration experiments suggest a cooperative amplification of asymmetry arising from extended conjugation and helical geometry during helix formation. Time-dependent density functional theory calculations are employed to support this hypothesis, showing that increasing conjugation length and helical order enhance the rotational strength of contributing excited states via elevated magnetic transition moments and improved alignment of electric and magnetic transition moments. Our findings provide a new polymer platform for designing functional chiral materials with tunable chiroptical and spin-dependent properties.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Atomic-Scale Imaging Reveals Polar-π Interactions in Two-Dimensional Molecular Superlattices

Controlling coassembly of synthetic oligomers into binary superlattices at the atomic level is challenging. Here, we report a strategy for programming polar-π interactions in oligomeric peptoids, a class of sequence-defined peptidomimetics, facilitating the formation of homogeneous two-dimensional (2D) superlattices. N-2-phenylethyl and N-(2-perfluorophenyl)ethyl side chains, similar in size, but with contrasting electrostatic characteristics, were introduced at defined sequence positions to generate favorable dipolar aromatic interactions. The resulting nanosheets exhibit different crystal motifs depending on the side chain interactions: systems containing only one type of aromatic side chain form a parallel V-shaped motif driven by π-π interactions, whereas a combination of both types of aromatic side chains, either within one backbone or through the coassembly of two distinct peptoids, adopt an antiparallel V-shaped superlattice with higher thermal stability, driven by polar-π interactions. Cryogenic transmission electron microscopy directly resolved the packing arrangement of perfluorophenyl and phenyl rings in individual nanosheet superlattices, confirming that intermolecular polar-π interaction dominates the superlattice motifs and increases lattice stability. Molecular dynamics simulations and density functional theory calculations further substantiate the energetic favorability of polar-π interactions over π-π interactions, rationalizing the formation of homogeneous superlattices with enhanced thermal stability. Our discoveries establish a design principle for binary coassembly using sequence-defined oligomers, which enables control over unit cell geometry, lattice stability, and molecular registration through aromatic side chain polarization and sequence control. This ability to program atomic-scale binary superlattices opens new avenues for designing functional 2D soft materials.

Lee, Yen Jea [Lawrence Berkeley National Laborator↗
DOE OSTI2026

Deterministic Control of Sn 3+ Valence and Electronic Phase Evolution in AgSnSe 2

Understanding how unusual oxidation states influence material properties is important for both fundamental science and energy applications. AgSnSe 2 is particularly intriguing because it stabilizes the rare and long-debated Sn 3+ oxidation state, whose true existence and role have remained enigmatic for many years. Here, in this work, we employ X-ray photoelectron spectroscopy, Mössbauer spectroscopy, and X-ray absorption spectroscopy to directly probe the oxidation state of Sn and its evolution under chemical substitution. All experimental evidence consistently confirms the presence of Sn in the +3 oxidation state in AgSnSe 2 . Complementary density functional theory calculations further corroborate this assignment. By substituting Sn with Sb, we systematically control the electronic state and its impact on the material’s physical properties. At low Sb concentrations, AgSnSe 2 retains superconductivity with a transition temperature of ∼5 K, while increasing Sb content deterministically drives a metallic-to-semiconducting transition through progressive suppression of superconductivity. Spectroscopic analyses show that Sb substitution provides deterministic control of the Sn oxidation state, evolving from a uniform +3 configuration in AgSnSe 2 to a mixed +2/+4 valence-skipping regime at higher Sb levels, thereby establishing a direct chemical handle over the material’s electronic phase. This tunability demonstrates that the Sn oxidation state in AgSnSe2 can be precisely engineered through Sb substitution, enabling controlled electronic phase transitions and establishing AgSnSe 2 as a promising platform for quantum and energy-related applications

crystal structure↗
DOE OSTI2026

Pseudo–Jahn–Teller Distortion in a One-Dimensional π-Conjugated Polymer

Structural distortions in low-dimensional π-conjugated systems profoundly influence their electronic properties, but the control of such behavior in laterally extended systems remains challenging. Here, in this study, we demonstrate that a one-dimensional conjugated polymer─ poly -(difluorenoheptalene-ethynylene) (PDFHE)─undergoes a pronounced out-of-plane backbone distortion, equivalent to a spontaneous symmetry breaking (SSB) of its mirror symmetry. We synthesized PDFHE on noble metal surfaces and characterized its structure and electronic states using low-temperature scanning tunneling microscopy (STM). Rather than adopting a planar, high-symmetry conformation, PDFHE relaxes into nonplanar isomers stabilized by a pseudo–Jahn–Teller (PJT) distortion having mirror-odd out-of-plane character. The distortion lowers the total energy and increases the band gap, providing a concise rationale for the observed symmetry breaking. Density functional theory calculations corroborate these findings, providing a microscopic explanation for the SSB. Our results show that even in mechanically robust extended π-systems, subtle electron–lattice coupling can spontaneously drive significant structural rearrangements, even in mechanically robust extended π-systems.

conformation↗
DOE OSTI2026

Ultrafast Formation of Jahn–Teller Polarons Revealed by State-Selective Excitation in Correlated Spinel Co 3 O 4

Jahn–Teller polarons are quasiparticles that stem from symmetry breaking and strong local electron–phonon coupling. They originate from an excess charge carrier being dressed by a local lattice distortion, caused by the Jahn–Teller effect, and they critically impact electrical, structural, and magnetic properties in transition metal oxides. The observation of the microscopic steps involved in their formation is essential for enabling control over material properties through the targeted activation of local, site-specific modifications with light pulses. While Jahn–Teller distortion associated with polaron formation was predicted to contribute significantly to changes in electronic band gap and optical properties in Co 3 O 4 , its experimental observation remains elusive, requiring signatures of local symmetry reduction. In this work, we demonstrate Jahn–Teller polaron formation in spinel Co 3 O 4 . By exciting electronic transitions at 3.10 eV and 1.55 eV, we target either the Oh Cobalt(III) or the Td Cobalt(II) ions, and drive the subsequent coherent responses of the system through two different pathways. For the former, we demonstrate that ligand-to-metal charge transfer leads to Jahn–Teller polaron formation, which is linked to the deformation potential and magnetoelastic coupling. For the latter, we identify the coherent excitation of a T 2g phonon mode launched by on-site d-d electronic transitions. Key to our observations is the ability to target site-specific electronic excitations in spinel Co 3 O 4 using ultrafast optical pulses, while monitoring the ensuing low-energy collective modes through the coherent time-domain response of the material. Our approach, which combines the comparative analysis of experimental fingerprints with the support from density functional theory calculations, is broadly applicable to systems in which Jahn–Teller polaron physics has been theoretically predicted but remains experimentally unverified, and it underscores the potential of electronic-state targeting as a route to selectively excite and probe quasiparticle dynamics in solids.

Lattices↗
DOE OSTI2026

Cyclodextrin-Derived Porous Liquids Enabled by In Situ Solvation Shell Formation

Porous liquids (PLs) represent a unique platform for molecular separations by combining permanent porosity with liquid-phase mobility. However, it remains a formidable challenge to construct and stabilize PLs with sub-5 Å pores using readily available porous host and liquid media. Here, we report the construction of cyclodextrin (CD)-derived PLs enabled by in situ solvation shell formation. The acid–base neutralization reaction between CD and an organic base was leveraged to generate a thin ionic solvation shell around the CD host, effectively liquefying CD and preventing its segregation in the liquid base medium while preserving accessible molecular-scale cavities. Spectroscopic analysis, neutron scattering, density functional theory calculations, and molecular dynamics simulations collectively confirm the structural evolution and existence of abundant internal porosity in PLs. The unique architectures of CD-derived PLs enable highly selective encapsulation of fluorinated alkanes and significantly enhanced uptake of inert gases. This facile and generalizable strategy enables construction of high-quality PLs with engineered ultramicroporosity to facilitate molecular separations.

Cavities↗
DOE OSTI2026

High-Rate, Selective Electrosynthesis of Cyclohexanone Oxime via In Situ Generation and Release of Hydroxylamine on Bismuth

Oxime compounds are key industrial intermediates for nylon precursors and commodity chemicals. However, conventional routes rely on multistep reactions and hydroxylamine (NH 2 OH) salts, raising significant safety and sustainability concerns. Although electrosynthesis offers an alternative, oxime formation on d-block transition metals suffers from poor selectivity, as nitrogen oxyanion intermediates bind strongly to the surface and are readily over-reduced to ammonia. Here, we report morphology-controlled p-block bismuth rhombic dodecahedra (Bi RDs) that promote in situ NH 2 OH generation and its desorption into the electrolyte, enabling an electrochemical-chemical decoupled route for cyclohexanone oxime (CHO) synthesis. Bi RDs deliver nearly 100% Faradaic efficiency (FE) at −0.5 V vs. RHE and a yield of 1.4 mmol h –1 cm –2 at −0.9 V vs. RHE in an H-cell, while maintaining a CHO selectivity of nearly 100% at 100 mA cm –2 in a flow cell. Under identical conditions, d-block electrodes (Cu, Pd, Ag) show FE below 30%. Density functional theory calculations reveal that Bi 6p orbital-derived surface states weaken intermediate binding and facilitate NH 2 OH desorption, suppressing over-reduction. Kinetic analysis, post-addition trapping experiments, and in situ ATR-FTIR and Raman spectroscopy suggest the following reaction mechanism: NH 2 OH is selectively generated at the electrode surface, released as a freely diffusing intermediate, and undergoes homogeneous condensation with cyclohexanone in the bulk electrolyte, bypassing the surface-confined Langmuir–Hinshelwood pathway. These findings demonstrate that regulating intermediate desorption through p-block orbital chemistry provides a general strategy for achieving high selectivity in electro-organic nitrogen synthesis.

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

Tuning Solid Electrolyte Interphase Formation before Plating Onset in Anode-Free Sodium Batteries

Sodium (Na) batteries are of growing interest due to the higher earth abundance of sodium than lithium, as well as their promising theoretical energy density when metallic Na anodes are used. However, Na plating and stripping are heavily influenced by the physicochemical properties of the solid electrolyte interphase (SEI), which is directly influenced by the solvent and salt used for the electrolyte. While most studies focus on the SEI that forms on the surface of Na metal after plating, we expand this analysis by identifying a nanoscale “pre-plating” SEI that forms on the current collector (CC) prior to the onset of Na plating. Here, we systematically investigate an array of Na salt and glyme solvents in the electrolyte and determine the associated impacts on pre-plating SEI formation on aluminum CCs. By combining analytical electrochemistry approaches with a multimodal suite of spectroscopy techniques (X-ray, infrared, and Raman), supported by density functional theory calculations, we reveal a direct correlation between the Na + coordination environment and pre-plating SEI composition. We find that longer-chain glymes produce larger proportions of organic alkoxide products in the interphase, consistent with increased Na + −glyme interactions, while the fraction of salt-derived inorganic products (e.g., NaF) correlates with Na + −anion coordination. These insights highlight the critical influence of electrolyte composition particularly solvent identity and Na + coordination on the initial SEI formation in anode-free Na batteries.

anode-free batteries↗
DOE OSTI2024

Ligand-modified nanoparticle surfaces influence CO electroreduction selectivity

Improving the kinetics and selectivity of CO 2 /CO electroreduction to valuable multi-carbon products is a challenge for science and is a requirement for practical relevance. Here we develop a thiol-modified surface ligand strategy that promotes electrochemical CO-to-acetate. We explore a picture wherein nucleophilic interaction between the lone pairs of sulfur and the empty orbitals of reaction intermediates contributes to making the acetate pathway more energetically accessible. Density functional theory calculations and Raman spectroscopy suggest a mechanism where the nucleophilic interaction increases the sp 2 hybridization of CO (ad) , facilitating the rate-determining step, CO* to (CHO)*. We find that the ligands stabilize the (HOOC–CH 2 )* intermediate, a key intermediate in the acetate pathway. In-situ Raman spectroscopy shows shifts in C–O, Cu–C, and C–S vibrational frequencies that agree with a picture of surface ligand-intermediate interactions. A Faradaic efficiency of 70% is obtained on optimized thiol-capped Cu catalysts, with onset potentials 100 mV lower than in the case of reference Cu catalysts.

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

Polarization-driven band topology evolution in twisted MoTe 2 and WSe 2

Motivated by recent experimental observations of opposite Chern numbers in R-type twisted MoTe 2 and WSe 2 homobilayers, we perform large-scale density-functional-theory calculations with machine learning force fields to investigate moiré band topology across a range of twist angles in both materials. We find that the Chern numbers of the moiré frontier bands change sign as a function of twist angle, and this change is driven by the competition between moiré ferroelectricity and piezoelectricity. Our large-scale calculations, enabled by machine learning methods, reveal crucial insights into interactions across different scales in twisted bilayer systems. The interplay between atomic-level relaxation effects and moiré-scale electrostatic potential variation opens new avenues for the design of intertwined topological and correlated states, including the possibility of mimicking higher Landau level physics in the absence of magnetic field.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Programmable quantum emitter formation in silicon

Abstract Silicon-based quantum emitters are candidates for large-scale qubit integration due to their single-photon emission properties and potential for spin-photon interfaces with long spin coherence times. Here, we demonstrate local writing and erasing of selected light-emitting defects using femtosecond laser pulses in combination with hydrogen-based defect activation and passivation at a single center level. By choosing forming gas (N 2 /H 2 ) during thermal annealing of carbon-implanted silicon, we can select the formation of a series of hydrogen and carbon-related quantum emitters, including T and C i centers while passivating the more common G-centers. The C i center is a telecom S-band emitter with promising optical and spin properties that consists of a single interstitial carbon atom in the silicon lattice. Density functional theory calculations show that the C i center brightness is enhanced by several orders of magnitude in the presence of hydrogen. Fs-laser pulses locally affect the passivation or activation of quantum emitters with hydrogen for programmable formation of selected quantum emitters.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Selective atomic sieving across metal/oxide interface for super-oxidation resistance

Abstract Surface passivation, a desirable natural consequence during initial oxidation of alloys, is the foundation for functioning of corrosion and oxidation resistant alloys ranging from industrial stainless steel to kitchen utensils. This initial oxidation has been long perceived to vary with crystal facet, however, the underlying mechanism remains elusive. Here, using in situ environmental transmission electron microscopy, we gain atomic details on crystal facet dependent initial oxidation behavior in a model Ni-5Cr alloy. We find the (001) surface shows higher initial oxidation resistance as compared to the (111) surface. We reveal the crystal facet dependent oxidation is related to an interfacial atomic sieving effect, wherein the oxide/metal interface selectively promotes diffusion of certain atomic species. Density functional theory calculations rationalize the oxygen diffusion across Ni(111)/NiO(111) interface, as contrasted with Ni(001)/NiO(111), is enhanced. We unveil that crystal facet with initial fast oxidation rate could conversely switch to a slow steady state oxidation.

(S)TEM, oxidizing metals↗