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DOE OSTI2026

Charge accumulation and solvation in $β$-NiOOH: Surface chemistry of an OER catalyst from ML-aided simulations

Electrochemical water splitting is a key technology for a sustainable energy transition, providing a route to store surplus electricity from renewable sources. A central bottleneck is the sluggish oxygen evolution reaction (OER), which drives the search for catalysts that are active, stable, and inexpensive enough for large-scale deployment. Within this context, pure and doped NiO x H y combine high activity with low cost, making them prime candidates for alkaline OER. Yet, despite extensive study, the atomistic structure of NiOOH under operando conditions and the associated reaction mechanisms remain debated. Here, we investigate the structural complexity of pure β-NiOOH, the scaffold for its doped derivatives. We systematically investigate the oxidation of the surface adsorbates via proton-coupled electron transfer steps across relevant facets and sites, identifying the most probable sequence of deprotonation events. Our results reveal asymmetric charge accumulation on Wulff-relevant surfaces and show how applied potential can promote morphological restructuring. Explicit solvation is included through machine-learning interatomic potential molecular dynamics of the NiOOH/water interface, which allows us to resolve the hydrophobic and hydrophilic character of different surfaces and the associated interfacial water structure. Together, these insights demonstrate how surface chemistry and solvation jointly govern the stability of NiOOH and the accumulation of surface charge, with possible implications for catalytic performance.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2016

Necessity of capillary modes in a minimal model of nanoscale hydrophobic solvation

Modern theories of the hydrophobic effect highlight its dependence on length scale, emphasizing the importance of interfaces in the vicinity of sizable hydrophobes. We recently showed that a faithful treatment of such nanoscale interfaces requires careful attention to the statistics of capillary waves, with significant quantitative implications for the calculation of solvation thermodynamics. Here, we show that a coarse-grained lattice model like that of Chandler [Chandler D (2005) Nature 437(7059):640-647], when informed by this understanding, can capture a broad range of hydrophobic behaviors with striking accuracy. Specifically, we calculate probability distributions for microscopic density fluctuations that agree very well with results of atomistic simulations, even many SDs from the mean and even for probe volumes in highly heterogeneous environments. This accuracy is achieved without adjustment of free parameters, because the model is fully specified by well-known properties of liquid water. As examples of its utility, we compute the free-energy profile for a solute crossing the air-water interface, as well as the thermodynamic cost of evacuating the space between extended nanoscale surfaces. These calculations suggest that a highly reduced model for aqueous solvation can enable efficient multiscale modeling of spatial organization driven by hydrophobic and interfacial forces.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2024

Interfacial solvation-structure regulation for stable Li metal anode by a desolvation coating technique

Rechargeable lithium (Li) metal batteries face challenges in achieving stable cycling due to the instability of the solid electrolyte interphase (SEI). The Li-ion solvation structure and its desolvation process are crucial for the formation of a stable SEI on Li metal anodes and improving Li plating/stripping kinetics. This research introduces an interfacial desolvation coating technique to actively modulate the Li-ion solvation structure at the Li metal interface and regulate the participation of the electrolyte solvent in SEI formation. Through experimental investigations conducted using a carbonate electrolyte with limited compatibility to Li metal, the optimized desolvation coating layer, composed of 12-crown-4 ether-modified silica materials, selectively displaces strongly coordinating solvents while simultaneously enriching weakly coordinating fluorinated solvents at the Li metal/electrolyte interface. This selective desolvation and enrichment effect reduce solvent participation to SEI and thus facilitate the formation of a LiF-dominant SEI with greatly reduced organic species on the Li metal surface, as conclusively verified through various characterization techniques including XPS, quantitative NMR, operando NMR, cryo-TEM, EELS, and EDS. The interfacial desolvation coating technique enables excellent rate cycling stability (i.e., 1C) of the Li metal anode and prolonged cycling life of the Li||LiCoO 2 pouch cell in the conventional carbonate electrolyte (E/C 2.6 g/Ah), with 80% capacity retention after 333 cycles.

42 ENGINEERING↗

DOE OSTI2024

Building an ab initio solvated DNA model using Euclidean neural networks

Accurately modeling large biomolecules such as DNA from first principles is fundamentally challenging due to the steep computational scaling of ab initio quantum chemistry methods. This limitation becomes even more prominent when modeling biomolecules in solution due to the need to include large numbers of solvent molecules. We present a machine-learned electron density model based on a Euclidean neural network framework that includes a built-in understanding of equivariance to model explicitly solvated double-stranded DNA. By training the machine learning model using molecular fragments that sample the key DNA and solvent interactions, we show that the model predicts electron densities of arbitrary systems of solvated DNA accurately, resolves polarization effects that are neglected by classical force fields, and captures the physics of the DNA-solvent interaction at the ab initio level.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2022

Imaging Wavepackets in Real-Space & Disentangling Ultrafast Solvation Dynamics with High-Energy Ultrafast X-ray Scattering

The microscopic information of solute and solute-solvent motions can be measured using ultrafast diffuse x-ray scattering, and compared to molecular dynamics simulations, as demonstrated in studies of solvated molecular systems done in X-ray free-electron lasers. However, for the typical photon energies used in these experiments, the photon momentum transfer range was limited to lower Q values where the signals arising from different parts of the studied system overlap significantly. Recently, this limitation was greatly alleviated by extending the photon energy at the Linac Coherent Light-Source (LCLS), significantly increasing the accessible momentum transfer range. This improvement is transformative for ultrafast diffuse x-ray scattering measurements, enabling for the first time to disentangle the solute scattering difference signal, that persists to higher Q values, from the bulk solvent and solute-solvent cross-terms difference signals. In addition, it enhances the prediction ability of modeling and simulation methods such as the hybrid QM/MM approach. The extended Q range also opens the way to resolve in real-space details regarding coherent wavepackets motions beyond their center-of-mass positions. Here, we present the first results on high-energy (18keV) diffuse x-ray scattering in solution, demonstrating high fidelity time-resolved scattering and analysis of the photoexcited model photocatalysts PtPOP ([Pt2(POP)4]4-), and IrDimen ([Ir2(dimen)4]2+) in several solvents. These complexes provide ideal systems for demonstrating the ability of high-Q ultrafast scattering and QM/MM simulations to decompose ultrafast solvation dynamics into specific changes in the solute-solvent pair distribution function with a particular focus on how electronically excited states change the interaction between the solvent and photo-catalytically active metal sites. We introduce an approach to further utilize the high-energy capability and demonstrate a single-shot ultra-wide-angle X-ray Scattering modality using two perpendicular detectors, spanning a scattering angle range of more than 100 degrees, allowing to extend the accessible momentum transfer range up to Q~14 Å-1. We develop a model-free method to invert the x-ray scattering signals and enable the recovery of multiple pair-density motions that happen simultaneously, allowing us to directly measure in real-space nuclear wavepacket motions. . [1] Natan, Adi. "Real-Space Inversion and Super-Resolution of Ultrafast X-ray Scattering using Natural Scattering Kernels." arXiv preprint arXiv:2107.05576 (2021)

Natan, Adi↗

DOE OSTI2025

Solvated Ionic Liquid-based Electrolytes: Experimental Characterization, Atomistic Modeling and Applications in Energy Storage

This study aimed on understanding the molecular structure and transport mechanisms of high-concentration lithium electrolytes, with a particular focus on solvate ionic liquids (SILs) based on glyme solvents, for use in next-generation, high-voltage energy storage systems. The hypothesis is that the composition of the solvents in these electrolytes can be designed and adjusted to control cation solvation, enabling charge transport via an ion-hopping mechanism. This mechanism resembles Grotthuss conduction of protons in water and is independent of electrolyte viscosity. The experimental studies employed linear and nonlinear infrared spectroscopy (FTIR and 2D IR), electrochemical measurements, and vibrational probes.

25 ENERGY STORAGE↗

DOE OSTI2022

The Solvation of the E. coli CheY Phosphorylation Site Mapped by XFMS

The Escherichia coli CheY protein belongs to a large bacterial response regulator superfamily. X-ray hydroxy radical foot-printing with mass spectroscopy (XFMS) has shown that allosteric activation of CheY by its motor target triggers a concerted internalization of aromatic sidechains. We reanalyzed the XFMS data to compare polar versus non-polar CheY residue positions. The polar residues around and including the 57D phosphorylated site had an elevated hydroxy radical reactivity. Bioinformatic measures revealed that a water-mediated hydrogen bond network connected this ring of residues with the central 57D. These residues solvated 57D to energetically stabilize the apo-CheY fold. The abundance of these reactive residues was reduced upon activation. This result was supported by the bioinformatics and consistent with the previously reported activation-induced increase in core hydrophobicity. It further illustrated XFMS detection of structural waters. Direct contacts between the ring residues and the phosphorylation site would stabilize the aspartyl phosphate. In addition, we report that the ring residue, 18R, is a constant central node in the 57D solvation network and that 18R non-polar substitutions determine CheY diversity as assessed by its evolutionary trace in bacteria with well-studied chemotaxis. These results showcase the importance of structured water dynamics for phosphorylation-mediated signal transduction.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2018

Do Better Quality Embedding Potentials Accelerate the Convergence of QM/MM Models? The Case of Solvated Acid Clusters

This study examines whether the use of more accurate embedding potentials improves the convergence of quantum mechanics/molecular mechanics (QM/MM) models with respect to the size of the QM region. In conjunction with density functional theory calculations using the ωB97X-D functional, various embedding potentials including the TIP3P water model, the effective fragment potential (EFP), and semi-empirical methods (PM6, PM7, and DFTB) were used to simulate the deprotonation energies of solvated acid clusters. The calculations were performed on solvated neutral (HA) and cationic (HB+) acids clusters containing 160 and 480 water molecules using configurations sampled from molecular dynamics simulations. Consistently, the ωB97X-D/EFP model performed the best when using a minimal QM region size. The performance for the other potentials appears to be highly sensitive to the charge character of the acid/base pair. Neutral acids display the expected trend that semi-empirical methods generally perform better than TIP3P; however, an opposite trend was observed for the cationic acids. Additionally, electronic embedding provided an improvement over mechanical embedding for the cationic systems, but not the neutral acids. For the best performing ωB97X-D/EFP model, a QM region containing about 6% of the total number of solvent molecules is needed to approach within 10 kJ mol−1 of the pure QM result if the QM region was chosen based on the distance from the reaction centre.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2026

Diffusion and Solvation Dynamics of Ions in Water: Beyond the Brownian Approximation

The coupled dynamics of ions and water molecules in their first hydration shell impact a variety of processes including ion diffusion, selective ion transport in water-filled nanopores, and the kinetics of ion-pairing, ion adsorption, and metal-ligand binding reactions. In this work, we study these coupled dynamics for alkali metals (Li, Na, K, Rb, Cs), alkaline Earth metals (Mg, Ca, Sr, Ba), and chloride through the lens of their dependence on ion isotopic mass. Results are validated against previous measurements of the isotopic mass-dependence of ion diffusion coefficients in water and previous ab initio calculations of ion high-frequency dynamics in water. We find that the vibrational power spectra of ions in water consistently exhibit either two or three peaks, i.e., ions have several rattling frequencies within their solvations shells as previously reported for a subset of the species examined here. These frequencies have different sensititivies to isotopic mass that may serve as signatures of ion solvation processes (such as the tendency of ions to orient their first-shell water molecules) and that also may relate to Hofmeister-like effects including the relative affinity of different metals for ribonucleic acid (RNA).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

NASA NTRS1969

Production of solvated electrons

Current research, both theoretical and experimental, relating to the production and kinetics of interactions of solvated electrons is reviewed. Particular attention is focused on solvated electrons generated by ionizing radiation in water, alcohols, and organic systems.

Thomas, J. K.↗

DOE OSTI2017

Systems and methods for producing metal clusters; functionalized surfaces; and droplets including solvated metal ions

The invention generally relates to systems and methods for producing metal clusters; functionalized surfaces; and droplets including solvated metal ions. In certain aspects, the invention provides methods that involve providing a metal and a solvent. The methods additionally involve applying voltage to the solvated metal to thereby produce solvent droplets including ions of the metal containing compound, and directing the solvent droplets including the metal ions to a target. In certain embodiments, once at the target, the metal ions can react directly or catalyze reactions.

36 MATERIALS SCIENCE↗

DOE OSTI2017

Systems and methods for producing metal clusters; functionalized surfaces; and droplets including solvated metal ions

36 MATERIALS SCIENCE↗

DOE OSTI2018

Systems and methods for producing metal clusters; functionalized surfaces; and droplets including solvated metal ions

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2019

Systems and methods for producing metal clusters; functionalized surfaces; and droplets including solvated metal ions

Cooks, Robert Graham↗

DOE OSTI2020

Systems and methods for producing metal clusters; functionalized surfaces; and droplets including solvated metal ions

36 MATERIALS SCIENCE↗

DOE OSTI2015

Improved Dielectric Solvation Model for Electronic Structure Calculations

This project was originally funded for the three year period from 09/01/2009 to 08/31/2012. Subsequently a No-Cost Extension was approved for a revised end date of 11/30/2013. The primary goals of the project were to develop continuum solvation models for nondielectric short-range interactions between solvent and solute that arise from dispersion, exchange, and hydrogen bonding. These goals were accomplished and are reported in the five peer-reviewed journal publications listed in the bibliography below. The secondary goals of the project included derivation of analytic gradients for the models, improvement of the cavity integration scheme, application of the models to the core-level spectroscopy of water, and several other miscellaneous items. These goals were not accomplished because they depended on completion of the primary goals, after which there was a lack of time for any additional effort.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

DOE OSTI2023

Electrolytes with Solvating Inner Sheath Engineering for Practical Na–S Batteries

Sodium–sulfur (Na–S) batteries with durable Na-metal stability, shuttle-free cyclability, and long lifespan are promising to large-scale energy storages. However, meeting these stringent requirements poses huge challenges with the existing electrolytes. Herein, a localized saturated electrolyte (LSE) is proposed with 2-methyltetrahydrofuran (MeTHF) as an inner sheath solvent, which represents a new category of electrolyte for Na–S system. Unlike the traditional high concentration electrolytes, the LSE is realized with a low salt-to-solvent ratio and low diluent-to-solvent ratio, which pushes the limit of localized high concentration electrolyte (LHCE). The appropriate molecular structure and solvation ability of MeTHF regulate a saturated inner sheath, which features a reinforced coordination of Na + to anions, enlarged Na + -solvent distance, and weakened anion-diluent interaction. Such electrolyte configuration is found to be the key to build a sustainable interphase and a quasi-solid–solid sulfur redox process, making a dendrite-inhibited and shuttle-free Na–S battery possible. With this electrolyte, pouch cells with decent cycling performance under rather demanding conditions are demonstrated.

25 ENERGY STORAGE↗

DOE OSTI2022

Uncovering the Solvation Structure of LiPF 6 –Based Localized Saturated Electrolytes and Their Effect on LiNiO 2 –Based Lithium–Metal Batteries

Electrolytes play a critical role in stabilizing highly reactive lithium-metal anodes (LMAs) and high-voltage cathodes for rechargeable lithium-metal batteries (LMBs). Localized high concentration electrolytes (LHCEs) have achieved remarkable success in the context of LMBs. However, the state-of-the-art LHCEs are based on LiFSI salt, which is prohibitively expensive. Here, the utility of low-cost LiPF 6 salt in localized saturated electrolytes (LSEs) with a series of solvents and diluents in LMBs with cobalt-free LiNiO 2 cathode is systematically explored. Experimental and theoretical analyses reveal that the unique solvation structure formed not only changes the distribution of solvents and anions but also alters the atom–atom distances within them, leading to different reduction and oxidation stabilities compared to low-concentration electrolytes. In addition, LSEs help form LiF-rich interphase layers on the LMA and LiNiO 2 cathode, protecting the electrodes from degradation during cycling. Different LSEs also lead to differences in lithium plating morphology and impedance buildup during cycling, impacting the performance of LMBs. Finally, the solvent and diluent must be carefully selected for compatibility with a lithium salt when developing LHCEs and LSEs for LMBs.

25 ENERGY STORAGE↗