Hydride Formation Research Articles

Evaluation of lithium as a tritium storage medium for betavoltaics

Lithium foils were demonstrated to absorb surrogate protium for tritium-powered betavoltaics. 20 μm thick lithium foils were hole-punched from a ribbon of electrodeposited lithium on copper foil. The lithium foils were loaded with hydrogen in a custom Sievert apparatus where the pressure drop showed full hydriding at a hydrogen pressure of 2 bar and at all loading temperatures above the lithium melting point at 190, 200, 225, 250, and 300. Lithium hydride formation was confirmed with Raman spectroscopy after hydrogen loading. The kinetics of experimental hydride formation was compared to the diffusion-limited Mintz–Bloch model. While the Mintz–Bloch model showed good fit with the experimental loadings, the model overpredicted the loading kinetics starting at 250 °C and at higher temperatures. The overprediction was either caused by lithium hydride outgassing due to some reduction with some residual lithium hydroxide created from brief air exposure when sealing the lithium in the reactor or a transition from diffusion-limited hydride growth to surface or metal–hydride interface-limited hydride growth.

SHINERS Study of Chloride Order-Disorder Phase Transition and Solvation of Cu(100).

Shell-isolated nanoparticle enhanced Raman spectroscopy (SHINERS) and density functional theory (DFT) are used to probe Cl- adsorption and the order-disorder phase transition associated with the c(2 × 2) Cl- adlayer on Cu(100) in acid media. A two-component ν(Cu-Cl) vibrational band centered near 260 ± 1 cm-1 is used to track the potential dependence of Cl- adsorption. The potential dependence of the dominant 260 cm-1 component tracks the coverage of the fluctional c(2 × 2) Cl- phase on terraces in good agreement with the normalized intensity of the c(2 × 2) superstructure rods in prior surface X-ray diffraction (SXRD) studies. As the c(2 × 2) Cl- coverage approaches saturation, a second ν(Cu-Cl) component mode emerges between 290 and 300 cm-1 that coincides with the onset and stiffening of step faceting where Cl- occupies the threefold hollow sites to stabilize the metal kink saturated Cu <100> step edge. The formation of the c(2 × 2) Cl- adlayer is accompanied by the strengthening of ν(O-H) stretching modes in the adjacent non-hydrogen-bonded water at 3600 cm-1 and an increase in hydronium concentration evident in the flanking H2O modes at 3100 cm-1. The polarization of the water molecules and enrichment of hydronium arise from the combination of Cl- anionic character and lateral templating provided by the c(2 × 2) adlayer, consistent with SXRD studies. At negative potentials, Cl- desorption occurs followed by development of a sulfate νs(S═O) band. Below -1.1 V vs Hg/HgSO4, a new 200 cm-1 mode emerges congruent with hydride formation and surface reconstruction reported in electrochemical scanning tunneling microscopy studies.

Electrochemical Hydrogen Charging on Corrosion Behavior of Ti-6Al-4V Alloy in Artificial Seawater

This study employs advanced electrochemical and surface characterization techniques to investigate the impact of electrochemical hydrogen charging on the corrosion behavior and surface film of the Ti-6Al-4V alloy. The findings revealed the formation of γ-TiH and δ-TiH2 hydrides in the alloy after hydrogen charging. Prolonging hydrogen charging resulted in more significant degradation of the alloy microstructure, leading to deteriorated protectiveness of the surface film. This trend was further confirmed by the electrochemical measurements, which showed that the corrosion resistance of the alloy progressively worsened as the hydrogen charging time was increased. Consequently, this work provides valuable insights into the mechanisms underlying the corrosion of Ti-6Al-4V alloy under hydrogen charging conditions.

Possible mechanism of hydride formation at interface

The theoretical aspects of the possible mechanism of hydride formation at the "metal-carbide inclusion" phase interface are considered. Hydrides create additional phase boundaries and constitute stress concentrators, which can lead to hydrogen embrittlement and delayed hydride cracking. This is important for high-alloy steels, for example, for bearing steels, operating under conditions of high-cycle surface loading and relatively elevated temperatures. A plane-stress model of surface loading has been developed in the ANSYS software package. Due to the calculations of the plane stresses state, it becomes possible to evaluate the probable places of hydrogen accumulation at the interface of the microstructural components phases of the material in the directions of plastic deformation development from the interface for possible hydride formation.

Heats of Formation on the Way from B2H6 to B20H16: Thermochemical Consequences of Multicenter Bonding in Ab initio and DFT Methods

The objective of this study is to evaluate the effectiveness of various computational methods in reproducing the experimental heats of formation of boron hydrides using the atomization energy ap- proach....

In situ interfacial reactions in hydride–oxide composite electrolytes for stable all-solid-state Li–metal batteries

Mechanochemical formation of hydride–oxide dual core–shell composite electrolytes is demonstrated for stable all-solid-state Li–metal batteries.

F-Block hydride complexes - synthesis, structure and reactivity.

Complexes formed between the heaviest and lightest elements in the periodic table yield the f-block hydrides, a unique class of compounds with wide-ranging utility and interest, from catalysis to light-responsive materials and nuclear waste storage. Recent developments in syntheses and analytics, such as exploiting low-oxidation state metal ions and improvements in X-ray diffraction tools, have transformed our ability to understand, access and manipulate these important species. This perspective brings together insights from binary metal hydrides, with molecular solution phase studies on heteroleptic complexes and gas phase investigations. It aims to provide an overview of how the f-element influences hydride formation, structure and reactivity including the sometimes-surprising power of co-ligands to tune their behaviour towards a variety of applications.

Effect of pre-deformation on hydrogen diffusion and hydrogen induced damage in commercially pure titanium

This work aims to elucidate the interaction between hydrogen atoms and pre-introduced dislocations in commercially pure titanium (CP-Ti). Positron annihilation spectroscopy supplemented by the first-principle calculations was utilized to reveal the effects of dislocation densities on the formation of hydride types and the concentration of hydrogen-induced defects in CP-Ti. Results show that, in the hydrogen-charged sample with 40 % deformation, hydrogen-induced damage gradually decreases when the hydrogen enters the sample at a depth of about 350 nm. This finding suggests that the high-density dislocations present in deformed specimens effectively trap hydrogen atoms and inhibit their diffusion, which ultimately mitigate damage within the samples. γ-TiH and δ-TiH2 hydrides are observed in the hydrogen-charged sample. The thermal desorption spectroscopy results show that the desorption amount of deuterium decreases from 1.14 × 1018 D/cm2 to 5.10 × 1017 D/cm2 with an increase in dislocation density because dislocations inhibit the diffusion of deuterium. In samples with higher deformation, the high dislocation density inhibits the formation of δ-TiH2 hydrides and promotes the formation of γ-TiH hydrides, which significantly reduce the hardening of samples. These results provide insight into the interaction of hydrogen with pre-introduced defects and provide strong theoretical support for the development and improvement of more damage-resistant materials.

The Mechanism of Titanium Hydride Formation on Grade-2 Titanium

ASTM Grade-2 titanium (Ti-2) is a commercially pure grade widely used for its corrosion resistance in extreme environments. Therefore, Ti-2 has found applications within industries such as oil and gas, chemical processing, and nuclear power, where it is used for components such as reaction vessels, piping, and heat exchangers. Challenges with the fabrication process result in relatively high amounts of iron in commercial materials such as Grade-2, Grade-7, and Grade-12, which all have a maximum tolerance of 0.3 wt.% iron.The amount of iron present in titanium has been shown to have a significant effect on the microstructure and corrosion behaviour[1]. For example, Fe will precipitate and form TixFe intermetallic particles (IMPs) along grain boundaries if the local solubility limit is exceeded. Many of the corrosion processes (e.g., crevice corrosion) that determine the long-term integrity of Ti are strongly affected by the presence of IMPs[1]. Another detrimental corrosion scenario is the formation of titanium hydride (TiHx), which can precipitate on the surface and/or in the bulk material when the hydrogen concentration is high enough. Formation of TiHx phases increases the susceptibility of the metal to cracking, as the hydride is less ductile than the metal and its formation results in a strain-inducing volume increase within the matrix. Despite the proven importance of IMPs to the corrosion behaviour of Ti, and the detrimental effects of hydride formation on the material’s integrity, a direct relationship between IMPs and TiHx formation is not well established. There is some evidence that titanium hydride formation initiates at IMPs[2], but a complete mechanistic understanding is missing.In this study, the initiation and propagation mechanism of TiHx formation on Ti-2 is being investigated over a 24-hour period. Hydrides were grown galvanostatically in a simulated crevice corrosion environment. The surface was analyzed at various times using field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), focused ion beam (FIB) milling, and X-ray diffraction (XRD). By visualizing TiHx within the matrix using FE-SEM, we determined that titanium hydride formation initiates at IMPs and then grows both laterally and vertically around the IMP. After reaching a depth of ~ 4 µm below the surface of the IMP, the hydride stops growing vertically but continues to spread laterally across the Ti grain face until full surface coverage is reached. Finally, a steady-state condition is reached, in which hydride is present as a uniformly distributed layer across the surface with a thickness of ~ 4 μm. Additionally, the electrochemical potential values during the galvanostatic hydride growth process and the amount of hydride detected using XRD both support the hypothesis of the hydride growing rapidly before reaching a limited thickness.[1] X. He, J. J. Noël, D. W. Shoesmith, Corrosion 2004, 60, 378–386.[2] Q. Tan, Z. Yan, H. Wang, D. Dye, S. Antonov, B. Gault, Scr. Mater. 2022, 213, 114640.

An Electrochemical Cell for Operando Grazing-Incidence X-Ray Absorption Spectroscopic Studies of Low-Loaded Electrodes

X-ray absorption spectroscopy (XAS) is a powerful technique that can provide element specific information on the local electronic and structural properties of newly developed electrocatalysts, especially when performed under operating conditions (i.e., operando). However, the large amounts of catalyst typically needed to achieve sufficiently high spectral quality and temporal resolution can result in working electrodes of several micrometers in thickness. This can in turn lead to an inhomogeneous potential distribution across the electrode, delamination and/or incomplete utilization of the catalyst layer, severe bubble formation and accumulation due to poor mass transport properties.[1, 2] In addition, the activity and selectivity of a catalyst are often measured in a different cell geometry (e.g., using rotating disk electrodes (RDEs)), leading to uncertainties in comparison with the results inferred from spectroscopic data.[3]To tackle these problems we have developed a new spectroelectrochemical XAS flow cell that enables spectral acquisition in fluorescence mode using an X-ray beam incidence angle of ≤ 0.1° with regards to the working electrode’s substrate plane, i.e., in a so called grazing incidence (GI) configuration (see Figure 1). In this acquisition configuration we successfully tracked the formation of palladium hydride with a time resolution of 10 seconds per spectrum while using a Pd-loading as low as 50 µgPd∙cm-2. Moreover, the careful design of the working electrode flow field allows the study of faradaic processes (e.g., O2-reduction) under mass-transport controlled conditions entailing currents comparable to those attained in RDE measurements (≤ 10 mA∙cm−2). The combination of these features with an ion-conductive membrane to separate the working- and counter-electrode compartments additionally enables the detection of gaseous products (e.g., from CO2-electroreduction) by degassing them out of the electrolyte and analyzing them in time-resolved fashion by means of mass spectrometry.[4] References Diklić, N., et al., Potential Pitfalls in the Operando XAS Study of Oxygen Evolution Electrocatalysts. ACS Energy Letters, 2022. 7(5): p. 1735-1740. Diercks, J.S., et al., Spectroscopy vs. Electrochemistry: Catalyst Layer Thickness Effects on Operando/In Situ Measurements. Angew Chem Int Ed Engl, 2023: p. e202216633. Diercks, J.S., et al., Interplay between Surface-Adsorbed CO and Bulk Pd Hydride under CO2-Electroreduction Conditions. ACS Catalysis, 2022: p. 10727-10741. Khanipour, P., et al., Electrochemical Real-Time Mass Spectrometry (EC-RTMS): Monitoring Electrochemical Reaction Products in Real Time. Angew Chem Int Ed Engl, 2019. 58(22): p. 7273-7277 Figure 1

Computational unravelling of cathodic hydride formation on palladium surfaces

Palladium (Pd) is well-known for its role in catalyzing hydrogen-based reduction reactions, owing to its excellent catalytic activity and hydrogen storage ability. Its surface and subsurface structures under electrochemical conditions are vital in understanding the hydrogen evolution reaction (HER) mechanism at the Pd cathodes where the most active sites are located on ‘in situ’ formed Pd-hydride layers. In this work, we investigate the process of Pd-hydride formation as well as the step-by-step formation and stability of Pd-hydride/Pd interfaces under electrochemical conditions using first-principles calculations. Our results reveal that among the low-indexed surfaces (111), (110) and (100), the (111) surface is expected to be the most dominant surface in a Pd nanostructure in addition to being the most preferred surface for hydrogen adsorption. Based on calculated Pourbaix diagrams, we can identify the relevant regions close to the equilibrium electrode potential and pH for proton electroreduction and hydrogen evolution, where the Pd surfaces start to be covered by hydrogen adatoms, and when the electrode potential is decreased, there are clear thermodynamic indications for more and more subsurface hydride layers. Overall, the results provide insights into the stability and formation of hydrogen-containing Pd surfaces, forming PdH/Pd type interfaces. Our idealized model systems are a first step towards elucidation of relevant active sites on Pd.

Thermodynamic calculations using reverse Monte Carlo: A computational workflow for accelerated construction of phase diagrams for metal hydrides

Metal hydrides are promising candidates for hydrogen storage applications. From a materials discovery perspective, an accurate, efficient computational workflow is urgently required that can rapidly analyze/predict thermodynamic properties of these materials. In this paper, we develop a thermodynamic property estimation/phase diagram construction framework based on the lattice reverse Monte Carlo (RMC) method. We apply the technique to the nickel hydride (NiHx) system by calculating the pressure-composition-temperature (PCT) isotherm and constructing its phase diagram. Formation of nickel hydride entails significant volume expansion, strong interaction between hydrogen and the host atoms, lattice strain, and a phase transition. An attractive feature of our approach is that the entire phase diagram can be accurately constructed in few minutes by considering <10 configurations. In contrast, a popular technique based on grand canonical Monte Carlo would require sampling of several million configurations. The promising results obtained with our computational workflow suggest that the approach can be used in future for wider materials search and discovery.

Oxidation of iron by giant impact and its implication on the formation of reduced atmosphere in the early Earth

Giant impact–driven redox processes in the atmosphere and magma ocean played crucial roles in the evolution of Earth. However, because of the absence of rock records from that time, understanding these processes has proven challenging. Here, we present experimental results that simulate the giant impact–driven reactions between iron and volatiles (H 2 O and CO 2 ) using x-ray free electron laser (XFEL) as fast heat pump and structural probe. Under XFEL pump, iron is oxidized to wüstite (FeO), while volatiles are reduced to H 2 and CO. Furthermore, iron oxidation proceeds into formation of hydrides (γ-FeH x ) and siderite (FeCO 3 ), implying redox boundary near 300-km depth. Through quantitative analysis on reaction products, we estimate the volatile and FeO budgets in bulk silicate Earth, supporting the Theia hypothesis. Our findings shed light on the fast and short-lived process that led to reduced atmosphere, required for the emergence of prebiotic organic molecules in the early Earth.

“Click” Chemistry Assisted Synthesis of Magnetite‐CNT Nanohybrid Supported Gold Nanoparticles for Enhanced Catalytic Reduction of 4‐Nitrophenol

AbstractThe magnetite (Fe3O4) nanoparticles were strategically tethered over carbon nanotube (CNT) templates by using UV light‐induced thiol‐yne “click” chemistry approach which was followed by immobilization of chitosan stabilized gold nanoparticles (Au NPs) onto this surface through electrostatic interactions. Their application as a magnetically recyclable catalyst was explored through the study of the model catalytic reaction of reduction of 4‐nitrophenol (4‐NP) in the presence of an excess of NaBH4. Kinetic studies on the reduction of 4‐nitrophenol revealed Au/Fe3O4−CNT ternary nanohybrids to serve as better catalytic systems compared to Au NPs. The catalytic reduction of 4‐NP was found to occur through the formation of active gold hydride (Au−H) species. The formation of Au−H species was facilitated by Au−Fe3O4 interaction through the transfer of hydride ions via dissociation of the B−H bond of the adsorbed borohydride ions [BH4]− and the heterolytic dissociation of molecular hydrogen (H2), produced on hydrolysis of NaBH4 on the surface of Au/Fe3O4. Moreover, the π–π interactions between the nitroaromatic ring of 4‐NP and the CNT surface are believed to facilitate their proximity. Further, on visible light irradiation, dissociation of H2 on the gold surfaces was enhanced by the localized surface plasmon resonance (LSPR)‐induced hot electrons.

Formation of silyl metal hydride, HMnSiH3 and silylidyne, H3ReSiH in the activation of silane by manganese and rhenium atoms

The reactions of laser ablated manganese and rhenium metal atoms with silane molecules in low temperature argon matrix were studied. The experimental and theoretical results indicate that the reaction happened after the metal atoms were excited to Mn(6P) or Re(6P) excited states upon photolysis. Combining the isotopic shifts of the infrared absorptions and quantum chemical calculations, the silyl metal hydride HMnSiH3 and the silylidyne H3ReSiH were identified in the argon matrix. The vibronic coupling between the ground state X2A' and the first excited state A2A'' leads to a bond angle H-Si-Re of 130.4° in the doublet ground state H3ReSiH.

Electrochemical hydrogen permeation in wrought and electron beam melted Ti-6Al-4V alloys

Ti-6Al-4V is one of the most widely used titanium alloys. However, it is susceptible to hydrogen embrittlement, e.g. due to hydride formation. Hydrogen permeability through Ti-based alloys is affected by the rapid formation of hydride or oxide surface layers as well as by trapping in the bulk alloy. Here, we analyze and compare the electrochemical hydrogen permeation (EHP) through wrought and electron beam melted (EBM) Ti-6Al-4V alloys. Hydrogen diffusion coefficients are calculated from the permeation current transients. The effective diffusion coefficient of hydrogen in the wrought alloy is found to be an order of magnitude higher than in the AM’ed alloy. The different microstructures of the wrought and EBM alloys are found to play an important role in hydrogen distribution and phase transformation in the alloy. In the EBM alloy, hydrogen is distributed more uniformly and, consequently, more pronounce phase transformations occur, eventually leading to brittle cracking. In the wrought alloy, on the other hand, hydrogen is distributed unevenly in the bulk of the membrane, forming hydride clusters, most probably at α/β interphase boundaries. These findings suggest that the EBM Ti-6Al-4V alloy is more susceptible to HE than its wrought counterpart.

An Investigation of Allyl-Substituted Bis(Diphosphine) Iron Complexes: Towards Precursors for Cooperative CO2 Activation.

In developing homogenous catalysts capable of CO2 activation, interaction with a metal center is often imperative. This work provides primary efforts towards the cooperative activation of CO2 using a Lewis acidic secondary coordination sphere (SCS) and iron via a paired theoretical/experimental approach. Specifically, this study reports efforts towards [Fe(diphosphine)2 (N2 )] as a CO2 -coordinated synthon where diphosphine=1,2-bis(di(3-cyclohexylboranyl)propylphosphino)ethane) (P2 BCy 4 ) or its precursor, 1,2-bis(diallylphosphino)ethane (tape). Initial efforts toward the {Fe(0)-N2 } complex were focused on deprotonation reactions of [Fe(diphosphine)2 (H)(NCCH3 )]+ and reduction of [Fe(tape)2 Cl2 ]. In the latter case, a mixture of intramolecularly π-bonded alkene and associated metallacyclic Fe(II)-H species were produced - heating this mixture provided the hydride as the major product. Notably, the interconversion of this pair counters that of related intermolecular reactions between [Fe(depe)2 ] (depe=1,2-bis(diethylphosphino)ethane) and ethylene, where hydride formation occurs subsequent to π-coordination; this has been probed by theoretical calculations. Finally, reactivity of the metallacyclic {Fe(II)-H} complex with CO2 was probed, resulting in a pair of isomeric ferra(II)lactones.

A microstructure-based modeling of delayed hydride cracking in Zr-2.5Nb pressure tube material

In this work, a microstructurally sensitive computational model is developed to simulate delayed hydride cracking (DHC) in Zr-2.5Nb alloy. The model is validated by comparing threshold stress intensity factor (KIH) predictions available in the literature. The anisotropy of Zr-2.5Nb is considered through microstructures containing grains and grain boundaries with different orientations and strengths at the mesoscale. A physically consistent damage model with evolving characteristics based on hydride formation is employed to simulate DHC. Results show that the grain anisotropy and grain boundary strength significantly affect the DHC, which may not be generally noticed in the traditional models.

Nitrogenase beyond the Resting State: A Structural Perspective.

Nitrogenases have the remarkable ability to catalyze the reduction of dinitrogen to ammonia under physiological conditions. How does this happen? The current view of the nitrogenase mechanism focuses on the role of hydrides, the binding of dinitrogen in a reductive elimination process coupled to loss of dihydrogen, and the binding of substrates to a binuclear site on the active site cofactor. This review focuses on recent experimental characterizations of turnover relevant forms of the enzyme determined by cryo-electron microscopy and other approaches, and comparison of these forms to the resting state enzyme and the broader family of iron sulfur clusters. Emerging themes include the following: (i) The obligatory coupling of protein and electron transfers does not occur in synthetic and small-molecule iron-sulfur clusters. The coupling of these processes in nitrogenase suggests that they may involve unique features of the cofactor, such as hydride formation on the trigonal prismatic arrangement of irons, protonation of belt sulfurs, and/or protonation of the interstitial carbon. (ii) Both the active site cofactor and protein are dynamic under turnover conditions; the changes are such that more highly reduced forms may differ in key ways from the resting-state structure. Homocitrate appears to play a key role in coupling cofactor and protein dynamics. (iii) Structural asymmetries are observed in nitrogenase under turnover-relevant conditions by cryo-electron microscopy, although the mechanistic relevance of these states (such as half-of-sites reactivity) remains to be established.

On the Shoulders of Giants-Reaching for Nitrogenase.

Only a single enzyme system-nitrogenase-carries out the conversion of atmospheric N2 into bioavailable ammonium, an essential prerequisite for all organismic life. The reduction of this inert substrate at ambient conditions poses unique catalytic challenges that strain our mechanistic understanding even after decades of intense research. Structural biology has added its part to this greater tapestry, and in this review, I provide a personal (and highly biased) summary of the parts of the story to which I had the privilege to contribute. It focuses on the crystallographic analysis of the three isoforms of nitrogenases at high resolution and the binding of ligands and inhibitors to the active-site cofactors of the enzyme. In conjunction with the wealth of available biochemical, biophysical, and spectroscopic data on the protein, this has led us to a mechanistic hypothesis based on an elementary mechanism of repetitive hydride formation and insertion.