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At least 1,117 records · Page 62
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Water Network Shape-Dependence of Local Interactions with the Microhydrated –NO 2 – and –CO 2 – Anionic Head Groups by Cold Ion Vibrational Spectroscopy

We report the structural evolutions of water networks and solvatochromic response of the CH 3 NO 2 – radical anion in the OH and CH stretching regions by analysis of the vibrational spectra displayed by cryogenically cooled CH 3 NO 2 – ·(H 2 O) n=1–6 clusters. The OH stretching bands evolve with a surprisingly large discontinuity at n = 6, which features the emergence of an intense, strongly red-shifted band along with a weaker feature that appears in the region assigned to a free OH fundamental. Very similar behavior is displayed by the perdeuterated carboxylate clusters, RCO 2 – ·(H 2 O) n=5–7 (R = CD 3 CD 2 ), indicating that this behavior is a general feature in the microhydration of the triatomic anionic domain and not associated with CH oscillators. Electronic structure calculations trace this behavior to the formation of a “book” isomer of the water hexamer that adopts a configuration in which one of the water molecules resides in an acceptor–acceptor–donor (AAD) (A = acceptor, D = donor) H-bonding site. Excitation of the bound OH in the AAD site explores the local network topology best suited to stabilize an incipient –XO 2 H–OH–(H 2 O) 2 intracluster proton-transfer reaction. These systems thus provide particularly clear examples where the network shape controls the potential energy landscape that governs water network-mediated, intracluster proton transfer. The CH stretching bands of the CH 3 NO 2 – ·(H 2 O) n=1–6 clusters also exhibit strong solvatochromic shifts, but in this case, they smoothly blue-shift with increasing hydration with no discontinuity at n = 6. Furthermore, this behavior is analyzed in the context of the solute-ion polarizability response and partial charge transfer to the water networks.

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

High-Temperature Reaction Kinetics of the e aq – and HO 2 • Radicals with Iron(II) Ions in Aqueous Solutions

Pulsed electron radiolysis was used to determine the chemical reaction kinetics and Arrhenius parameters for iron(II) reactions in aqueous solutions under irradiation. The second-order Fe 2+ reactions with the hydrated electron (e aq – ) and the perhydroxyl radical (HO 2 • ), arising from water radiolysis, were measured to high temperatures using custom-built flow-through cells with a multichannel optical detection system. The reaction with the HO 2 • radical was found to proceed via the formation of a metal-ion adduct species, Fe 2+ –HO 2 • . Additionally, the adduct’s molar extinction coefficient and its first-order decay rate coefficients are reported.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2024

Photoelectron Spectroscopy and Computational Study on Microsolvated [B 10 H 10 ] 2– Clusters and Comparisons to Their [B 12 H 12 ] 2– Analogues

Microhydrated closo-Boranes have attracted great interests due to their superchaotropic activity related to well-known Hofmeister effect and important applications in biomedical and battery fields. In this work, we report a combined negative ion photoelectron spectroscopy and quantum chemical investigation on hydrated closo-decaborate clusters [B 10 H 10 ] 2- ·nH 2 O (n = 1 – 7) with a direct comparison to their analogues [B 12 H 12 ] 2- ·nH 2 O and free water clusters. A single H 2 O molecule is found sufficient to stabilize the intrinsically unstable [B 10 H 10 ] 2- dianion. The first two water molecules strongly interact with the solute forming B-H···H-O dihydrogen bonds while additional water molecules show substantially reduced binding energies. Unlike [B 12 H 12 ] 2- ·nH 2 O possessing highly structured water network with the attached H 2 O molecules arranged in a unified pattern by maximizing B-H···H-O dihydrogen bonding, distinct structural arrangements of the water clusters within [B 10 H 10 ] 2– ·nH 2 O are achieved with the water cluster networks from trimer to heptamer resembling free water clusters. Such a distinct difference arises from the variations in size, symmetry, and charge distributions between these two dianions. Finally, the present finding again confirms the structural diversity of hydrogen-bonding networks in microhydrated closo-boranes and enrich our understanding of aqueous borate chemistry.

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

Formation of Water Networks on Anionic Perylene

We present infrared photodissociation spectra of hydrated perylene anion clusters with up to four water molecules, as well as electronic structure calculations based on density functional theory. Water molecules form weak hydrogen bonds to the π system of the perylene anion. For clusters with more than one water molecule, water−water hydrogen bonds are formed, which generally appear to be stronger than water−π hydrogen bonds, especially for the trihydrate and tetrahydrate. The resulting water networks exist as water subclusters on the surface of the carbon frame of perylene. Here, we observe temperature-dependent dynamic effects, which highlight large amplitude motions of the water network and the shallowness of the potential energy surfaces governing the structures of these clusters.

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

Hydrolysis Reaction Pathways of Thorium Oxide Nanoclusters

Density functional theory benchmarked by correlated molecular orbital theory is used to develop a fundamental and predictive understanding of the interaction of thorium oxide nanoclusters with gas phase water to provide insight into nuclear-waste storage, production of thorium nuclear reactor fuels, and reprocessing of spent fuel. The structures of Th n O 2n (n = 3 – 6) clusters and their interactions with water have been studied at the B3LYP, MP2, and CCSD(T) levels. Hydrolysis is initiated by the formation of Lewis acid-base adducts, with relative H 2 O binding energies (physisorption) ranging from −15 kcal/mol to −22 kcal/mol. The initial H 2 O physisorption energy is ca. −21 kcal/mol regardless of the cluster size and is consistent with the experimentally obtained initial adsorption energy on a thorium dioxide surface. The physisorption enthalpies for additional water molecules can be affected by the presence of terminal groups OH groups generated by proton transfer to a Th-O near the site of adsorption. The hydrolysis products (chemisorption) form either bridging or terminal hydroxides. More exothermic hydrolysis steps were predicted for the formation of terminal hydroxides as compared to the formation of bridging hydroxides. Here, the calculated transition state barriers for transfer of protons from bound water complexes to form the chemisorption products are very low. Overall, water readily reacts with thorium oxide clusters preferring hydroxide products over hydrated complexes. First and second order fits were predicted for the combined physisorption and chemisorption energies for the hydrolysis of thorium oxide clusters. Finally, ionization energies and electron affinities were calculated as were HOMO-LUMO gaps to provide additional insights into the properties of the thorium oxide and hydroxide clusters.

Adsorption↗
DOE OSTI2026

Uranium Hexafluoride Hydrolysis Reaction Dynamics from Cryogenic Layering, FTIR Spectroscopy, and Isotopic Substitution

The first direct evidence that the hydrolysis reaction of uranium hexafluoride (UF 6 ) follows multiple competing pathways which are driven by the ratio of water to UF 6 , temperature, and isotopic composition is presented. Using temperature dependent infrared spectroscopy, it is shown the hydrolysis can be prevented at temperatures below 150 K, and that water-rich environments promote the formation of uranium oxyfluoride intermediates. Spectral shifts reveal isomeric transitions and the growth of polymeric species, with reaction reversibility observed at high water concentrations. Additionally, controlled heating rates affect the emergence of intermediates. The final particulate product consistently forms as uranyl fluoride hydrate, though its morphology and spectral signature vary with reaction conditions and annealing. These findings help clarify long-standing uncertainties surrounding UF 6 hydrolysis.

Chemical reactions↗
DOE OSTI2021

Pushing and Pulling: A Dual pH Trigger Controlled by Varying the Alkyl Tail Length in Heme Coordinating Peptide Amphiphiles

Some organisms in nature that undergo anaerobic respiration utilize 1D nanoscale arrays of densely packed cytochromes containing the molecule heme. The assemblies can be mimicked with 1D nanoscale fibrils composed of peptide amphiphiles designed to coordinate heme in dense arrays. To create such materials and assemblies it is critical to understand the assembly process and what controls the various aspects of hierarchical assembly. MD simulations suggest that shorter alkyl chains on the peptide lead to more dynamic structures than the peptides with longer chains that yield kinetically trapped states. The hydration parameters manifest themselves experimentally through the observation of a dual pH trigger which controls the peptide assembly rate, the heme binding affinity, and heme organization kinetics. Great strides in understanding the relative complexity of the self-assembly process in relation to incorporating a functional moiety like heme opens up many possibilities in developing abiotic assemblies for bioelectronic devices and assemblies

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

Structure of Sulfuric Acid Solutions Using Pair Distribution Function Analysis

Solvation and mesoscale ordering of sulfuric acid and other strong acid solutions leads to suppressed freezing points and strong rheological changes with varying concentration. While the solid-state structures are well-understood, studies focused on the evolving solvation structure in the solution phase have probed a limited concentration range (~1–6 M). This study applies a total scattering approach in both the wide-angle X-ray scattering (WAXS) and pair distribution function (PDF) regimes to elucidate the evolving solvation structure over its full range of acid concentration (0–18 M). The emergence of a prepeak in the WAXS regime at intermediate concentrations indicates a transition from noninteracting sulfate molecules in the dilute limit to sterically limited sulfates at concentrations near its deep eutectic point. Fits to the PDF data quantify this trend, showing a transition from octahedrally hydrated sulfates up to 6–7 M concentrations, followed by gradual dehydration, and eventually reaching a solution structure similar to that of water-in-salt electrolyte systems at high acid concentrations.

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

Development of $\mathrm{AMOEBA}$ Polarizable Force Field for Rare-Earth La 3+ Interaction with Bioinspired Ligands

Rare-earth metals (REMs) are crucial for many important industries, such as power generation and storage, in addition to cancer treatment and medical imaging. One promising new REM refinement approach involves mimicking the highly selective and efficient binding of REMs observed in relatively recently discovered proteins. However, realizing any such bioinspired approach requires an understanding of the biological recognition mechanisms. In this report we developed a new classical polarizable force field based on the AMOEBA framework for modeling a lanthanum ion (La 3+ ) interacting with water, acetate, and acetamide, which have been found to coordinate the ion in proteins. The parameters were derived by comparing to high-level ab initio quantum mechanical (QM) calculations that include relativistic effects. The AMOEBA model, with advanced atomic multipoles and electronic polarization, is successful in capturing both the QM distance-dependent La 3+ –ligand interaction energies and experimental hydration free energy. A new scheme for pairwise polarization damping (POLPAIR) was developed to describe the polarization energy in La 3+ interactions with both charged and neutral ligands. Simulations of La3+ in water showed water coordination numbers and ion–water distances consistent with previous experimental and theoretical findings. Water residence time analysis revealed both fast and slow kinetics in water exchange around the ion. This new model will allow investigation of fully solvated lanthanum ion–protein systems using GPU-accelerated dynamics simulations to gain insights on binding selectivity, which may be applied to the design of synthetic analogues.

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

Elucidating the Mechanism for the Reaction of $o$-Phthalaldehyde with Primary Amines in the Presence of Thiols

The use of o-phthalaldehyde (OPA) in combination with a thiol reagent is a common method for detecting primary amines in amino acids, peptides, and proteins. Despite its widespread use, the exact reaction mechanism has been debated since the 1980s. Here, we measure the kinetics of the reaction between OPA, alanine, and a dithiol (1,4-dithiolthreitol, DTT) as a function of pH and reagent concentration. Using these new measurements and accompanying kinetic models, we find evidence that the pH dependence of the kinetics arises from both the protonation states of alanine and DTT, the hydration state of OPA, and the unproductive equilibrium with DTT, all of which are pH-dependent. Importantly, these results support the mechanism originally proposed by Sternson [Rational design and evaluation of improved o-phthalaldehyde-like fluorogenic reagents. Anal. Biochem. 1985, 144, 233–246] and Wong [Reaction of o-phthalaldehyde with alanine and thiols: kinetics and mechanism. J. Am. Chem. Soc. 1985, 107, 6421–6422], in which the primary amine first reacts with OPA, followed by a reaction with the thiol to form the fluorescent isoindole product.

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

Modeling the Behavior of Complex Aqueous Electrolytes Using Machine Learning Interatomic Potentials: The Case of Sodium Sulfate

Understanding the structure and thermodynamics of solvated ions is essential for advancing applications in electrochemistry, water treatment, and energy storage. While ab initio molecular dynamics methods are highly accurate, they are limited by short accessible time and length scales whereas classical force fields struggle with accuracy. Herein, we explore the structure and thermodynamics of complex monovalent-divalent ion pairs using Na 2 SO 4 (aq) as a case study by applying a machine learning interatomic potential (MLIP) trained on density functional theory (DFT) data. Our MLIP-based approach reproduces key bulk properties such as density and radial distribution functions of water. We provide the hydration structure of the sodium and sulfate ions in the 0.1–2 M concentration range and the one-dimensional and two-dimensional potentials of mean force for the sodium–sulfate ion pairing at the low concentration limit (0.1 M), which are inaccessible to DFT. At low concentrations, the sulfate ion is strongly solvated, leading to the stabilization of solvent-separated ion pairs over contact ion pairs. Minimum energy pathway analysis revealed that coordinating two sodium ions with a sulfate ion is a multistep process whereby the sodium ions coordinate to the sulfate ion sequentially. Finally, we demonstrate that MLIPs allow the study of solvated ions beyond simple monovalent pairs with DFT-level accuracy in their low concentration limit (0.1 M) via statistically converged properties from ns-long simulations.

anions↗
DOE OSTI2020

Probing Pore Size and Connectivity in Porous Silicas Using 13C MAS NMR Spectroscopy of Supercritical Methane

Measuring the pore size and pore-size distributions and exploring the fluid-exchange dynamics between different types of pores in porous materials remains a significant experimental challenge but is critical to understanding catalysis, chromatography, nutrient cycling, and a whole range of geochemical phenomena, including shale gas and tight gas extraction. Here, we present the results of 1D 13 C NMR and 2D exchange spectroscopy (EXSY) NMR investigations of a porous silica using supercritical methane (scCH 4 ) as a direct probe of pore size and fluid exchange between pore types. The results show that the 13 C chemical shift of scCH 4 adsorbed in nanometer-scale silica pores becomes more negative with increasing pore diameter, in agreement with trends reported for gas hydrates, zeolites, MOFs, and clays and other microporous (<10 nm pores) geochemical materials. These 13 C chemical shifts follow a natural log–linear trend with pore size in the vacuum-dried porous silicas studied here, allowing one to predict pore size based on the 13 C chemical shift in dry silica nanopores. The EXSY and 1D 13 C NMR results both show that CH 4 exchanges between pore and bulk fluid environments over rate scales from 0.01 to 1 kHz in vacuum-dried samples and that exchange dynamics must be considered when interpreting 13 C NMR of pore-adsorbed CH 4 . Introducing H 2 O to the system causes the 13 C chemical shift to become more negative with increasing H 2 O content as a result of H 2 O preferentially filling small pores, forcing CH 4 to occupy larger pores that are better connected to the bulk environment. Likewise, the 1D 13 C data show a decreased distribution of exchange rates between pore-adsorbed and bulk CH 4 in the presence of H 2 O.

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

Role of the Solvent–Surfactant Duality of Ionic Liquids in Directing Two-Dimensional Particle Assembly

Nanoparticle self-assembly plays a key role in formation of superlattices, which exhibit remarkable physical and chemical properties. However, controlling assembly remains a challenge partly due to a lack of understanding of the assembly dynamics and the difficulty in linking interfacial solution properties to interparticle forces. In this study, using liquid-cell transmission electron microscopy, self-assembly of gold nanoparticles (NPs) into superlattices in mixtures of water and ionic liquid (IL) was visualized, revealing a dual role of the IL in the assembly process. At intermediate concentrations, the IL acts as a surfactant stabilizing the particles at a well-defined equilibrium separation corresponding to the length of hydrogen bonded IL cations adsorbed onto neighboring NPs. Analysis of the interparticle forces reveals attractive long-range interactions of a van der Waals nature. At separations of 1-3 nm, interactions are dominated by attractive ion correlation and repulsive hydration forces giving rise to an energy minimum at 1.5 nm separation. The superlattice is further stabilized by hydrogen bonding, which shifts the equilibrium interparticle distance to 1.1 nm. In contrast, at higher concentrations, IL accumulates and forms a structured network in the gap between nanoparticles, where it acts as a solvent that eliminates the repulsive barrier and thus promotes particle coalescence. This solvent-surfactant duality of IL opens new opportunities for their use in directing particle assembly.

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

Quantitative Cu Counting Methodologies for Cu/SSZ-13 Selective Catalytic Reduction Catalysts by Electron Paramagnetic Resonance Spectroscopy

Here, two Cu/SSZ-13 selective catalytic reduction (SCR) catalysts with distinct Si/Al ratios and isolated Z2Cu and ZCuOH distributions are prepared for in situ electron paramagnetic resonance (EPR) spectroscopic studies. These in situ studies include dehydration, titration of dehydrated samples with NO+O 2 and NH 3 , titration of NH 3 saturated samples with NO+O 2 , and finally steady-state standard NH 3 -SCR reaction. During dehydration, EPR active hydrated ZCuOH loses H 2 O ligands and becomes EPR silent due to a pseudo Jahn-Teller effect; a portion of ZCuOH also undergoes autoreduction to ZCu(I) species, a process that also induces EPR invisibility. During NO+O 2 treatment of dehydrated samples, ZCu(I) species are oxidized to Cu(II)-NO 3 - species, regaining EPR visibility. During NH3 titration, EPR silent dehydrated ZCuOH can also regain EPR visibility by coordinating with NH 3 ligands. During NO+O 2 titration of NH 3 -saturated samples, EPR active Cu contents first decrease due to Cu(II) reduction to Cu(I), and then increase due to Cu(II)-NO 3 - species formation. However, the Cu(II)-NO 3 - formation chemistry is substantially slower for the Si/Al = 36 catalyst. In steady-state SCR studies, the EPR active content decreases with increasing temperature in the kinetically controlled low-temperature regime and becomes largely invariant in mass-transfer limited regime. Importantly, Cu sites in the SCR more active Si/Al = 6 catalyst display substantially higher EPR visibility than the SCR less active Si/Al = 36 catalyst at any reaction temperatures tested. The higher Cu loading for the former catalyst is believed to be key for this difference.

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

Effect of Background Electrolyte Composition on the Interfacial Formation of Th(IV) Nanoparticles on the Muscovite (001) Basal Plane

Understanding the impact of actinide nanoparticle (NP) formation is important to assess radionuclide mobility in the environment. We combined surface X-ray diffraction (SXRD) and in situ AFM to investigate the previously reported unusual electrolyte effects on Th uptake on mica. At low [Th] (0.1 mM), interfacial structures show a broad Th electron density (~50 Å). A linear decrease of Th uptake with decreasing hydration enthalpy of the electrolyte cation (Li+, K+, NH4+, and Cs+) indicates a competitive effect between Th and the electrolyte cation. Na+ is a clear outlier from this trend. In situ AFM imaging confirms the results. Particles show a vertical size of ~1–2 nm and larger lateral dimensions of ~10–20 nm, which is typical for particles formed at interfaces (heterogeneous nucleation). At high [Th] = 1 and 3 mM, all investigated electrolytes (ACl, A = Li+, Na+, K+) show similar Th uptake, indicating a much smaller impact of electrolyte composition. The interfacial structures are dominated by a high Th loading at a distinct distance (~6.5 Å) from the surface. Therefore, the main retention mechanism at high [Th] is suggested to be the sorption of Th NPs aggregated from Th oligomers present in solution (homogeneous nucleation).

Neumann, J↗
DOE OSTI2022

Elucidating the Atomic Structures of the Gel Layer Formed during Aluminoborosilicate Glass Dissolution: An Integrated Experimental and Simulation Study

The altered glasses produced during aqueous dissolution of silicate and borosilicate glasses are among the most complex structures to understand at the atomic level due to their amorphous nature, random porosity and various levels of hydration. In this study, we gained insights of the complex atomic structures of altered aluminoborosilicate glasses by combining a range of experimental and computational approaches. The altered glasses were prepared by dissolution of three glasses with varying level of alumina in acid for 7 days. A comprehensive set of experimental [elemental analysis, high-energy X-ray diffraction, 29 Si and 27 Al solid-state nuclear magnetic resonance (NMR), and O 1s X-ray photoelectron spectroscopy (XPS)] and modeling (molecular dynamics (MD) simulations using non-reactive and reactive force fields) were used to study the atomic structures of these altered glasses. Elemental analysis showed that most of the B in the pristine glasses was leached into the solution and was not contained in the altered glass. The 29 Si and 27 Al solid-state NMR spectra revealed that the altered glasses have more polymerized silicate network as compared to those in the pristine glasses due to the reformation of linkages among Si and Al oxygen polyhedral in the altered glasses. The bridging and non-bridging (or hydroxyl O) atoms in the altered glasses were also quantified from their O 1s XPS spectra. Atomic structure models of the altered glasses were constructed by using MD simulations using the reactive force field based on the compositional information obtained from experiments. Various pore structures were generated using the charge-scaling (CS) method by using different initial densities and CS temperatures; the best CS parameters of each alternated glass were then determined by comparing with the experimental structure factors obtained from high energy X-ray diffraction. Pore and the atomic structures and vibrational properties around these pore surfaces were analyzed. Furthermore, these results from this comprehensive study thus provides a realistic insight into the pore morphology, atomic structure, and vibrational properties of altered glasses.

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

Selective Hydroxylation of In 2 O 3 as A Route to Site-Selective Atomic Layer Deposition

We report that several atomic layer deposition (ALD) processes are now known that leverage the distinct surface chemistry of two disparate substrates (e.g., metal vs oxide) to realize markedly different ALD nucleation rates in an approach referred to as area-selective ALD. In contrast, few ALD processes have been identified that allow selective reaction at distinct surface sites of a single material surface, in a process that might be called site-selective ALD (SS-ALD). We describe one potential strategy to discriminate among several distinct surface sites on bixbyite In 2 O 3 to achieve site selectivity. Using density functional theory, we predict the discriminant hydration and hydroxylation of In 2 O 3 terrace and step-edge sites that depend strongly on the substrate temperature at low water coverage. Infrared measurement of surface hydroxyls on In 2 O 3 nanoparticles supports the predicted temperature dependence. The in situ examination of MgO ALD nucleation also shows results consistent with the predicted temperature dependence of In 2 O 3 hydroxylation. Together, these findings suggest that a selective hydroxylation approach may be a viable route to SS-ALD on In 2 O 3 .

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

Dynamics of Electric Polarization and Relaxation of Ions at Humid Calcite Surfaces

Mobile ions at mineral surfaces can respond to an applied electric field, adopting a new distribution that effectively represents polarization of the electrical double layer. When the field is released, the ions relax to their equilibrium distribution. In both cases, the dynamics are characteristic of the interface. However, current models of electrokinetic phenomena are not sufficiently robust to accurately predict collective ion dynamics at structurally and chemically specific mineral–water interfaces. Here, in this study, we use electrostatic force microscopy (EFM) to investigate the dynamics of ion relaxation at hydrated calcite (104) surfaces at controlled relative humidity (RH). Electrically biased probes are used to polarize the distributions of calcium and carbonate ions that are intrinsic to this interface across a range of RH values. Polarization kinetics are tracked by monitoring the tip–sample force gradient during charging, and EFM imaging is used to characterize the spatial relaxation dynamics after the applied field is released. Electrostatic finite element modeling of the sample/probe system across length-scales from nanometers to millimeters reproduces the observed stretched exponential charging response. Together, these results allow us to estimate the ion diffusivities at the interface across a wide range of RH values. These diffusivities increase by roughly 5 orders of magnitude as the RH is increased from 5 to 90%, highlighting the critical role of adsorbed water for surface ion solvation that enables ion mobility.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗