Elucidating the Discharge Behavior of Aqueous Zinc Sulfur Batteries in the Presence of Molybdenum(IV) Chalcogenide Catalyst: The Criticality of Interfacial Electrochemistry.

The aqueous zinc-sulfur battery holds promise for significant capacity and energy density with low cost and safe operation based on environmentally benign materials. However, it suffers from the sluggish kinetics of the conversion reaction. Here, we highlight the efficacy of molybdenum(IV) sulfide (MoS) to reduce the overpotential of S-ZnS conversion in aqueous electrolytes and study the discharge products formed at the solid-solid and solid-liquid interfaces using experimental and theoretical approaches.

PH-sensitive adriamycin hydrochloride and oxaliplatin dual-loaded microspheres synergistically enhance local injections effect of hepatocellular carcinoma.

Chemotherapy is the primary palliative treatment for advanced hepatocellular carcinoma (HCC). However, the systemic delivery is associated with the drawbacks including a high risk of adverse effects and a low efficacy. Therefore, local injection therapy may be beneficial.

Emerging Atomistic Modeling Methods for Heterogeneous Electrocatalysis.

Heterogeneous electrocatalysis lies at the center of various technologies that could help enable a sustainable future. However, its complexity makes it challenging to accurately and efficiently model at an atomic level. Here, we review emerging atomistic methods to simulate the electrocatalytic interface with special attention devoted to the components/effects that have been challenging to model, such as solvation, electrolyte ions, electrode potential, reaction kinetics, and pH.

Accurate, Uncertainty-Aware Classification of Molecular Chemical Motifs from Multimodal X-ray Absorption Spectroscopy.

Accurate classification of molecular chemical motifs from experimental measurement is an important problem in molecular physics, chemistry, and biology. In this work, we present neural network ensemble classifiers for predicting the presence (or lack thereof) of 41 different chemical motifs on small molecules from simulated C, N, and O K-edge X-ray absorption near-edge structure (XANES) spectra. Our classifiers not only achieve class-balanced accuracies of more than 0.

Simulated sulfur K-edge X-ray absorption spectroscopy database of lithium thiophosphate solid electrolytes.

X-ray absorption spectroscopy (XAS) is a premier technique for materials characterization, providing key information about the local chemical environment of the absorber atom. In this work, we develop a database of sulfur K-edge XAS spectra of crystalline and amorphous lithium thiophosphate materials based on the atomic structures reported in Chem. Mater.

Deciphering phase evolution in complex metal oxide thin films via high-throughput materials synthesis and characterization.

Discovery of structure-property relationships in thin film alloys of complex metal oxides enabled by high-throughput materials synthesis and characterization facilities is demonstrated here with a case-study. Thin films of binary transition metal oxides (Ti-Zn) are prepared by pulsed laser deposition with continuously varying Ti:Zn ratio, creating combinatorial samples for exploration of the properties of this material family. The atomic structure and electronic properties are probed by spatially resolved techniques including x-ray absorption near edge structures (XANES) and x-ray fluorescence (XRF) at the Ti and Zn K-edge, x-ray diffraction, and spectroscopic ellipsometry.

Water Formation Reaction under Interfacial Confinement: AlSiO on O-Ru(0001).

Confined nanosized spaces at the interface between a metal and a seemingly inert material, such as a silicate, have recently been shown to influence the chemistry at the metal surface. In prior work, we observed that a bilayer (BL) silica on Ru(0001) can change the reaction pathway of the water formation reaction (WFR) near room temperature when compared to the bare metal. In this work, we looked at the effect of doping the silicate with Al, resulting in a stoichiometry of AlSiO.

Exfoliating silica bilayers via intercalation at the silica/transition metal interface.

The growth of the silica (SiO) bilayer (BL) films on transition metal (TM) surfaces creates a new class of two-dimensional (2D) crystalline, self-contained materials that interact weakly with the TM substrate. The BL-silica/TM heterojunction has shown unique physical and chemical properties that can lead to new chemical reaction mechanisms under the sub-nm confinement and broad potential applications ranging from surface protection, nano transistors, molecular sieves to nuclear waste removal. Novel applications of BL-silica can be further explored as a constituent of van der Waals assembly of 2D materials.

Valence-to-core X-ray emission spectroscopy of titanium compounds using energy dispersive detectors.

X-ray emission spectroscopy (XES) of transition metal compounds is a powerful tool for investigating the spin and oxidation state of the metal centers. Valence-to-core (vtc) XES is of special interest, as it contains information on the ligand nature, hybridization, and protonation. To date, most vtc-XES studies have been performed with high-brightness sources, such as synchrotrons, due to the weak fluorescence lines from vtc transitions.

Kinetic Limitations in Single-Crystal High-Nickel Cathodes.

High-nickel cathodes attract immense interest for use in lithium-ion batteries to boost Li-storage capacity while reducing cost. For overcoming the intergranular-cracking issue in polycrystals, single-crystals are considered an appealing alternative, but aggravating concerns on compromising the ionic transport and kinetic properties. We report here a quantitative assessment of redox reaction in single-crystal LiNi Mn Co O using operando hard X-ray microscopy/spectroscopy, revealing a strong dependence of redox kinetics on the state of charge (SOC).

Measuring Charge Transfer between Adsorbate and Metal Surfaces.

Charge transfer between dissimilar atoms is an essential step for many chemical processes such as corrosion and heterogeneous catalysis, but directly probing the charge transfer has been a challenge. Using the oxygen-copper system as an example, we show that synchrotron-based ambient pressure X-ray photoelectron spectroscopy can be employed to monitor the charge transfer between adsorbates and metal surfaces. It is shown that oxygen chemisorption on Cu surfaces results in an Auger process that differs from the photoexcitation-induced Coster-Kroning transition and can be used to derive the degree of charge transfer in combination with ab initio calculations.

Machine-Learning X-Ray Absorption Spectra to Quantitative Accuracy.

Simulations of excited state properties, such as spectral functions, are often computationally expensive and therefore not suitable for high-throughput modeling. As a proof of principle, we demonstrate that graph-based neural networks can be used to predict the x-ray absorption near-edge structure spectra of molecules to quantitative accuracy. Specifically, the predicted spectra reproduce nearly all prominent peaks, with 90% of the predicted peak locations within 1 eV of the ground truth.

Kinetic pathways of ionic transport in fast-charging lithium titanate.

Fast-charging batteries typically use electrodes capable of accommodating lithium continuously by means of solid-solution transformation because they have few kinetic barriers apart from ionic diffusion. One exception is lithium titanate (LiTiO), an anode exhibiting extraordinary rate capability apparently inconsistent with its two-phase reaction and slow Li diffusion in both phases. Through real-time tracking of Li migration using operando electron energy-loss spectroscopy, we reveal that facile transport in Li TiO is enabled by kinetic pathways comprising distorted Li polyhedra in metastable intermediates along two-phase boundaries.

Ultrathin Amorphous Titania on Nanowires: Optimization of Conformal Growth and Elucidation of Atomic-Scale Motifs.

Due to its chemical stability, titania (TiO) thin films increasingly have significant impact when applied as passivation layers. However, optimization of growth conditions, key to achieving essential film quality and effectiveness, is challenging in the few-nanometers thickness regime. Furthermore, the atomic-scale structure of the nominally amorphous titania coating layers, particularly when applied to nanostructured supports, is difficult to probe.

Determination of the structure and geometry of N-heterocyclic carbenes on Au(111) using high-resolution spectroscopy.

N-heterocyclic carbenes (NHCs) bind very strongly to transition metals due to their unique electronic structure featuring a divalent carbon atom with a lone pair in a highly directional sp-hybridized orbital. As such, they can be assembled into monolayers on metal surfaces that have enhanced stability compared to their thiol-based counterparts. The utility of NHCs to form such robust self-assembled monolayers (SAMs) was only recently recognized and many fundamental questions remain.

Identification of dopant site and its effect on electrochemical activity in Mn-doped lithium titanate.

Doped metal oxide materials are commonly used for applications in energy storage and conversion, such as batteries and solid oxide fuel cells. The knowledge of the electronic properties of dopants and their local environment is essential for understanding the effects of doping on the electrochemical properties. Using a combination of X-ray absorption near-edge structure spectroscopy (XANES) experiment and theoretical modeling we demonstrate that in the dilute (1 at.

Nonresonant valence-to-core x-ray emission spectroscopy of niobium.

The valence-to-core (V2C) portion of x-ray emission spectroscopy (XES) measures the electron states close to the Fermi level. These states are involved in bonding, thus providing a measure of the chemistry of the material. In this article, we show the V2C XES spectra for several niobium compounds.

Multi-Stage Structural Transformations in Zero-Strain Lithium Titanate Unveiled by in Situ X-ray Absorption Fingerprints.

Zero-strain electrodes, such as spinel lithium titanate (LiTiO), are appealing for application in batteries due to their negligible volume change and extraordinary stability upon repeated charge/discharge cycles. On the other hand, this same property makes it challenging to probe their structural changes during the electrochemical reaction. Herein, we report in situ studies of lithiation-driven structural transformations in LiTiO via a combination of X-ray absorption spectroscopy and ab initio calculations.

Supervised Machine-Learning-Based Determination of Three-Dimensional Structure of Metallic Nanoparticles.

Tracking the structure of heterogeneous catalysts under operando conditions remains a challenge due to the paucity of experimental techniques that can provide atomic-level information for catalytic metal species. Here we report on the use of X-ray absorption near-edge structure (XANES) spectroscopy and supervised machine learning (SML) for refining the 3D geometry of metal catalysts. SML is used to unravel the hidden relationship between the XANES features and catalyst geometry.

Reversible structure manipulation by tuning carrier concentration in metastable CuS.

The optimal functionalities of materials often appear at phase transitions involving simultaneous changes in the electronic structure and the symmetry of the underlying lattice. It is experimentally challenging to disentangle which of the two effects--electronic or structural--is the driving force for the phase transition and to use the mechanism to control material properties. Here we report the concurrent pumping and probing of CuS nanoplates using an electron beam to directly manipulate the transition between two phases with distinctly different crystal symmetries and charge-carrier concentrations, and show that the transition is the result of charge generation for one phase and charge depletion for the other.

Immobilization of single argon atoms in nano-cages of two-dimensional zeolite model systems.

The confinement of noble gases on nanostructured surfaces, in contrast to bulk materials, at non-cryogenic temperatures represents a formidable challenge. In this work, individual Ar atoms are trapped at 300 K in nano-cages consisting of (alumino)silicate hexagonal prisms forming a two-dimensional array on a planar surface. The trapping of Ar atoms is detected in situ using synchrotron-based ambient pressure X-ray photoelectron spectroscopy.

Surface Proton Transfer Promotes Four-Electron Oxygen Reduction on Gold Nanocrystal Surfaces in Alkaline Solution.

Four-electron oxygen reduction reaction (4e-ORR), a key pathway in energy conversion, is preferred over the two-electron reduction pathway that falls short in dissociating dioxygen molecules. Gold surfaces exhibit high sensitivity of the ORR pathway to its atomic structures. A long-standing puzzle remains unsolved: why the Au surfaces with {100} sub-facets were exceptionally capable to catalyze the 4e-ORR in alkaline solution, though limited within a narrow potential window.

Insights into the spurious long-range nature of local r-dependent non-local exchange-correlation kernels.

A systematic route to go beyond the exact exchange plus random phase approximation (RPA) is to include a physical exchange-correlation kernel in the adiabatic-connection fluctuation-dissipation theorem. In the previous study [D. Lu, J.