Hydride Formation Research Articles

Interaction between Hydrogen and Magnesium Films: From Hydrogenochromism to Applications.

Hydrogen, as a promising clean energy carrier, underscores the critical need for reliable detection technologies to ensure its safe and efficient use. Magnesium (Mg) thin films, with their hydrogenochromic properties, are particularly well-suited for hydrogen sensing applications due to their dramatic optical transitions. However, practical implementation faces challenges in achieving both rapid response and durability under cyclic conditions. To overcome these limitations, advanced interfacial tuning techniques have been developed to optimize hydrogen diffusion pathways and reinforce structural resilience. This review focuses on the scientific mechanism governing the interaction between Mg-based thin films and hydrogen, highlighting their suitability as hydrogen sensors with superior hydrogenochromic characteristics. Controllable manufacturing methods allow precise control over the alloy composition and microstructure of Mg-based thin films, facilitating the construction of phases and interfaces conducive to support efficient hydride formation, ultimately improving hydrogen response performance. Recent advancements in microstructure engineering, refined in situ characterization techniques, and promising optical applications drive the rapid development of Mg-based thin films.

Platinum hydride formation during cathodic corrosion in aqueous solutions.

Cathodic corrosion is an electrochemical phenomenon that etches metals at moderately negative potentials. Although cathodic corrosion probably occurs by forming a metal-containing anion, such intermediate species have not yet been observed. Here, aiming to resolve this long-standing debate, our work provides such evidence through X-ray absorption spectroscopy. High-energy-resolution X-ray absorption near-edge structure experiments are used to characterize platinum nanoparticles during cathodic corrosion in 10 mol l-1 NaOH. These experiments detect minute chemical changes in the Pt during corrosion that match first-principles simulations of X-ray absorption spectra of surface platinum multilayer hydrides. Thus, this work supports the existence of hydride-like platinum during cathodic corrosion. Notably, these results provide a direct observation of these species under conditions where they are highly unstable and where prominent hydrogen bubble formation interferes with most spectroscopy methods. Therefore, this work identifies the elusive intermediate that underlies cathodic corrosion.

Effect of Hydride Types on the Fracture Behavior of a Novel Zirconium Alloy Under Different Hydrogen-Charging Current Densities.

Hydrogen embrittlement is a critical issue for zirconium alloys, which receives long-term attention in their applications. The formation of brittle hydrides facilitates crack initiation and propagation, thereby significantly reducing the material's ductility. This study investigates the tensile properties and hydride morphology of a novel zirconium alloy under different hydrogen-charging current densities ranging from 0 to 300 mA/cm2, aiming to clarify the influence of hydrides on the fracture behavior of the alloy. The mechanical property results reveal that, as the hydrogen-charging current density increases from 0 to 100 mA/cm2, the maximal elongation decreases from 24.99% to 21.87%. When the current density is further increased from 100 mA/cm2 to 200 mA/cm2, the maximal elongation remains basically unchanged. However, a substantial drop in elongation is observed as the hydrogen-charging current density rises from 200 mA/cm2 to 300 mA/cm2, decreasing from 20.77% to 15.18%, which indicates a marked deterioration in hydrogen embrittlement resistance. Subsequently, phase compositions, fracture morphology, and hydride types in the fracture region of tensile specimens were characterized. The morphology and quantity of hydrides change with increasing hydrogen-charging current density. When the hydrogen-charging current density reaches 100 mA/cm2, the δ-phase hydrides form, which significantly reduces the ductility of the zirconium alloy. At a hydrogen-charging current density of 200 mA/cm2, metastable ζ-phase hydrides are formed, resulting in negligible variations in the alloy's mechanical properties. However, when it comes to 300 mA/cm2, stable δ-phase hydrides with diverse morphologies form, leading to a pronounced degradation in tensile performance. Finally, by integrating mechanical tests with microstructural characterization, the influence of hydrides formed under different hydrogen-charging current densities on the zirconium alloy was analyzed. With increasing hydrogen-charging current density, the maximal elongation of the specimens gradually decreases, while the tensile strength steadily increases. At a hydrogen-charging current density of 300 mA/cm2, a larger amount of hydrides is formed, and the hydride type transitions completely from a mixture of δ-phase and ζ-phase hydrides to entirely δ-phase hydrides. The formation of lath-like δ-phase hydrides induces twinning structures, resulting in further lattice mismatch, which significantly reduces the maximal elongation of the zirconium alloy. Additionally, the morphology of the δ-phase hydrides changes from slender needle-like structures to lath-like structures, leading to a notable increase in internal stress, which in turn further enhances the tensile strength of the specimens.

Organoselenium Ligand Enabled Selective Electron Tuning for Switchable Hydrogen Evolution Reaction.

Unraveling the electronic structure of metal complexes can bring various catalytic possibilities for hydrogen evolution reaction (HER).However, the electronic effect of metal and ligands modulating and switching the reaction center for HER has yet to be comprehensively analyzed.Herein, we report nickel selenoether electrocatalysts which show tunable reaction centers (nickel or ligand) for HER using mild weak acetic acid in less deprotonating DMF solvent.Synthesized nickel selenoether electrocatalysts which follow a ligand-centered pathway demonstrated remarkably high turnover frequency (kobs) upto 14000 s-1 with 93% Faradaic Efficiency (F.E.).Whereas Ni-electrocatalyst having N-donor and selenoether ligands follow a metal-centered HER and show kobs value of 2110 s-1 with F.E. of 98%. A kinetic isotopic effect (KIE) study using CD3CO2D provides kH/kD = 0.49 and 13.01 values for two types of catalysts suggestive of metal-centered and ligand-centered catalytic behavior, respectively.Also, EPR studies revealed nickel-centered and ligand-centered radicals in two types of Ni-electrocatalysts. Mechanistically, the EPR, CV, and DFT computation studies suggest that the electron density of the selenoether ligand plays a crucial role by acting as an electron reservoir in deciding the reaction pathways, whether hydride formation occurs at metal-centered leading to Ni-H intermediate or ligand-centered pathways for HER.

Phthalimidine Synthesis via Iridium-Catalyzed Reductive Lactamization.

Herein, we report a sustainable and efficient method for the synthesis of structurally diverse phthalimidines from 2-formylbenzoic acid and primary amines using an iridium-catalyzed reductive lactamization strategy. The advantages of this method, such as the use of water-ethanol as a solvent, broad substrate scope, high catalyst efficiency (S/C up to 10000), good scalability, and easy purification, enable it to be a practical approach to phthalimidines. It is suggested that iridium hydride formation is involved in the rate-limiting step. Synthetic applications for the late-stage functionalization of medicinally relevant molecules are also demonstrated.

Effects of hydrogen on microstructure evolution and mechanical properties of TB8 titanium alloy.

The influence of varying hydrogen content on the microstructure, mechanical properties, and fracture behavior of the metastable β titanium alloy TB8 after hydrogen charging has been investigated in this study. Several characterization methods, including optical microscopy (OM), x-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), were employed to comprehensively analyze the alloy. The results show that with the addition of hydrogen, hydrogen mainly accumulated at grain boundaries in the form of hydrides. The β phase diffraction peak shifted to a lower angle, which can be attribute to hydrogen-induced lattice distortion. As the hydrogen content increases, γ-TiH hydrides and ε-TiH2 hydrides were observed. Ultimate tensile strength of the alloy firstly increased from 982 MPa to 1636 MPa, and then decreased to 1432 MPa. Uniform elongation decreased from 33% to 19%. Fracture mode transitioned from ductile to brittle with increasing hydrogen. In summary, we hope the outcome of this work could provide important insights toward the hydrogen charging influences the microstructure, mechanical properties, and fracture behavior of the TB8 titanium alloy.

Hydride formation in open thin film metal hydrogen systems: Cahn-Hilliard-type phase-field simulations coupled to elasto-plastic deformations

Hydride formation in open thin film metal hydrogen systems: Cahn-Hilliard-type phase-field simulations coupled to elasto-plastic deformations

Kinetic study of catalytic formic acid dehydrogenation by in situ UV-vis spectroscopy

We developed an in situ UV-vis spectroscopy method to study formic acid dehydrogenation kinetics. This method revealed hydride formation and H2 evolution rates, highlighting the need to enhance both steps to improve catalyst activity.

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 provides information about the electronic and local geometric structural properties of newly developed electrocatalysts, especially when it is 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 (CL), as well as to the (partial) shielding of the CL with electrochemically evolved bubbles trapped within its pores. These limitations can be tackled by performing such spectrochemical measurements with low-loaded (and thus thin) electrodes, which call for the acquisition of XAS spectra in fluorescence mode and using an X-ray beam incidence angle of ≤0.1° with regards to the working electrode's substrate plane in a grazing-incidence (GI) configuration. Thus, in this work, we introduce a new spectroelectrochemical flow cell that allows one to perform such measurements in this GI mode and verify its functionality by tracking the potential-induced formation of palladium hydride (PdHx) in a Pd nanoparticle-based electrocatalyst. A time resolution of 10 s per spectrum was achieved with a very low Pd-loading of only 30 μgPd/cm2. Moreover, the implementation of an ion-conductive membrane to separate the working- and counter-electrode compartments enables the quantification of reaction products, which, in the case of gaseous species, can be detected in a time-resolved manner by means of mass spectrometry. Chiefly, this allows us to determine the electrocatalytic activity and selectivity of a given material in the same cell configuration used for the spectroscopic measurements and assures a reliable comparison among the results derived from both techniques.

Numerical computations on thermal performance of large-scale Ti-Mn-based metal hydride storage reactor via open source CFD software

Certain metals and metal alloys can absorb hydrogen through an exothermic chemical reaction, resulting in the formation of metal hydrides. To maintain a rapid charging rate, the produced heat must be extracted as rapidly as it is generated. This study was attempted to evaluate the heat transfer enhancement in a cylindrical hydrogen storage reactor equipped with a central tube for large-scale applications using a 3D transient model. Finite-volume simulations are carried out using the open-source software package OpenFOAM to systematically investigate the impacts of material thermophysical properties, cooling media, and heat exchanger design on the heat transfer behaviors and hydrogen storage rate. The reactor’s performance was evaluated in terms of temperature and total hydrogen mass history profiles, in addition to pressure drop. The findings indicated that the charging time was improved by roughly 86%, compared to the case without thermal enhancement to attain 90% hydrogen storage capacity. A diminished pressure drop was observed between the water-based Al2O3 nanofluid with 5 vol% concentration and pure water at lowered coolant flow velocities, hence enhancing pumping power efficiency. Moreover, the results demonstrated that the storage rate is markedly improved by enhancing the effective thermal conductivity of the hydride bed, increasing the heat exchange area, accelerating the coolant flow rate, and lowering its temperature. The outcomes highlighted the possibility of advancing the current metal hydride reactor for practical application.

Hydride-Induced Reconstruction of Pd Electrode Surfaces: A Combined Computational and Experimental Study.

Designing electrocatalysts with optimal activity and selectivity relies on a thorough understanding of the surface structure under reaction conditions. In this study, experimental and computational approaches are combined to elucidate reconstruction processes on low-index Pd surfaces during H-insertion following proton electroreduction. While electrochemical scanning tunneling microscopy clearly reveals pronounced surface roughening and morphological changes on Pd(111), Pd(110), and Pd(100) surfaces during cyclic voltammetry, a complementary analysis using inductively coupled plasma mass spectrometry excludes Pd dissolution as the primary cause of the observed restructuring. Large-scale molecular dynamics simulations further show that these surface alterations are related to the creation and propagation of structural defects as well as phase transformations that take place during hydride formation.

Magnetically retrievable carbon-wrapped CNT/Ni nanospheres as efficient catalysts for nitroaromatic reduction.

We present a facile strategy for synthesizing magnetically retrievable carbon-wrapped CNT/Ni nanospheres (C-wrapped CNT/Ni) that enhance the catalytic performance of metals for environmental pollutant reduction. Structural and compositional analyses using X-ray diffraction (XRD), Raman spectroscopy, energy-dispersive X-ray spectroscopy (EDS), and field emission scanning electron microscopy (FESEM) confirmed the phase purity, morphology, and structure of the C-wrapped CNT/Ni. XRD, Raman, and EDS data validate the formation of the nanospheres, while FESEM images reveal uniform Ni nanospheres wrapped with a carbon layer through interconnected, evenly dispersed CNTs. Initially, Ni nanoparticles were anchored onto multiwalled carbon nanotubes to form magnetic CNT/Ni nanospheres, which were then coated with a carbon layer to prevent aggregation, improve Ni particle stability, and introduce additional surface functionalities. The catalytic efficacy of C-wrapped CNT/Ni was assessed through the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). The reaction rate constant (k app = 0.6167 min-1) with C-wrapped CNT/Ni is approximately six times higher than that with bare Ni nanospheres (k app = 0.1056 min-1). This enhanced catalytic activity is attributed to the synergistic effect between the spherical Ni core and the wrapped carbon layer, mediated by the interconnected CNT, which promotes efficient hydride formation. Additionally, C-wrapped CNT/Ni demonstrates exceptional reusability in the 4-NP reduction process. The integration of these features within a single framework suggests its significant potential for diverse engineering and environmental applications.

On the role of hydrogen bond acceptors in electrocatalytic hydride formation

On the role of hydrogen bond acceptors in electrocatalytic hydride formation

Theoretical modeling of experimental isotherms for hydrogen storage in La0.9Ce0.1Ni5 alloy

This research reports the results of an experimental and numerical analysis of the La0.9Ce0.1Ni5 alloy's hydrogen absorption and desorption isotherms at three distinct temperatures (T = 313 K, 333 K, and 353 K). We first determined the morphological and structural properties, as well as the hydrogen storage isotherms, of the intermetallic La0.9Ce0.1Ni5 experimentally. The experimental isotherms were then compared to a mathematical model based on statistical physical theory. Due to the good agreement between the experimental isotherms and the proposed model, the insertion and release of hydrogen atoms (nα, nβ), geometric densities of receptor sites (Nαm, Nβm), and absorption-desorption energies (Pα, Pβ) were determined. Moreover, thermodynamic functions like enthalpy, entropy, Gibbs free energy, and internal energy were calculated using these parameters. The findings demonstrated that the intermetallic compound's CaCu5 structure promotes the formation of stable metal hydrides through attractive interactions, ensuring that hydrogen atoms are securely trapped in the metal lattice, thereby enhancing the material's hydrogen storage capacity.

DFT investigations of doping effects on the structural stability, thermal diffusion, and absorption/desorption kinetics in cubic, hexagonal, and monoclinic Mg2NiHx hydrides

The pseudo-potential plane-wave method, based on Density Functional Theory (DFT) and using the Generalized Gradient Approximation (GGA), is applied to investigate the effects of progressive hydrogen insertion on the structural stability and energetics of Mg2NiHx hydrides. The obtained results indicate that Mg2Ni crystallizes in the hexagonal (P6222) structure. Taking into account the site preference of H atoms, the progressive hydrogenation of Mg2Ni favors the formation of Mg2NiHx hydrides in cubic (Fm-3m) and monoclinic (C2/c) phases rather than the parent hexagonal phase. The alloying effects of Cu, Y, Si, Ti, Cr, and Fe on the structural stability and absorption/desorption kinetics of monoclinic Mg2NiH4 are also investigated. More particularly, systems with Cu and Si additions have the lowest desorption temperatures, as confirmed by Molecular Dynamic (MD) calculations. The thermal diffusion is well observed in all studied compounds. The corresponding average thermal diffusion coefficients are mainly attributed to hydrogen atoms and are increased by the addition of Cu. These trends are expected to have an important role in phase transitions observed during hydrogen insertion. The present study based on DFT and MD calculations shows that doped Mg2NiHx are promising hydrides with interesting kinetic behavior. The obtained results can be useful for future experimental studies devoted to improving hydrogen absorption/desorption temperatures, low energy costs, and high atomic hydrogen storage capacities in Mg2Ni.

The Coupling of Synthesis and Electrochemistry to Enable the Reversible Storage of Hydrogen as Metal Hydrides.

Given its high gravimetric energy density and status as a clean fuel when derived from renewables, hydrogen (H2) is considered a premier candidate for energy storage; however, its low volumetric density limits its broader application. Chemical storage through the reversible incorporation of H2 into chemical bonds offers a promising solution to its low volumetric density, circumventing subpar energy densities and substantial infrastructure investments associated with physical storage methods. Metal hydrides are promising candidates for chemical storage because of their high gravimetric capacity and tunability through nanostructuring and alloying. Moreover, metal hydride/H2 interconversion may be interfaced with electrochemistry, which offers potential solutions to some of the challenges associated with traditional thermochemical platforms. In this Perspective, we describe anticipated challenges associated with electrochemically mediated metal hydride/H2 interconversion, including thermodynamic efficiencies of metal hydride formation, sluggish kinetics, and electrode passivation. Additionally, we propose potential solutions to these problems through the design of molecular mediators that may control factors such as metal hydride solubility, particle morphology, and hydride affinity. Realization of an electrochemically mediated metal hydride/H2 interconversion platform introduces new tools to address challenges associated with hydrogen storage platforms and contributes toward the development of room-temperature hydrogen storage platforms.

Direct Imaging of Electrochemical Palladium Hydride Formation from PdCoO2 for Highly Efficient Hydrogen Evolution Reaction

Active and reliable electrocatalysts are fundamental to renewable energy technologies.[1] PdCoO2 has recently been recognized as a promising catalyst for the hydrogen evolution reaction (HER) in acidic media.[2] This study unveils the activation mechanism of PdCoO2, highlighting two key processes: the leaching of Co atoms from the structure and the formation of palladium hydride (PdHx) nanoparticles.The former process is studied by operando measurement of Co dissolution and found to be kinetically related to the HER. Scanning electron microscopy cross-sections of PdCoO2 after prolonged HER reveal a thorough transformation towards the PdHx phase. The as-formed hydride nanoparticles were found to be stable up to anodic potentials of 0.8 V (with respect to reversible hydrogen electrode at pH = 1).The latter, i.e. the formation of hydrides, is confirmed through secondary ion mass spectrometry and quantitatively analyzed by atom probe tomography. By employing deuterium as a proxy for hydrogen, we identified the PdDx phase and determined a D/Pd atomic ratio of 0.28.Our findings highlight the critical role of palladium hydride formation in understanding the high performance of the HER catalyst derived from PdCoO2, offering insights into the design of more efficient electrocatalysts for renewable energy technologies.

Titanium Hydride Growth and Tix Fe Intermetallic Particle Dissolution on Grade-2 Titanium Under Simulated Crevice Corrosion Conditions

ASTM Grade-2 titanium (Ti-2) is a commercially pure grade of titanium with a combination of high strength, excellent ductility, and elite corrosion resistance. That determines its use in diverse and demanding applications, including use as components in flue-gas desulphurization plants, exhaust systems in the automotive industry, and multiple components in marine equipment.Crevice corrosion and hydrogen embrittlement are the common failure mechanisms for Ti-2 components. Crevice corrosion involves the development of occluded cell corrosion conditions characterized by a solution consisting of low [O2] and low pH. Under these conditions, the hydrogen evolution reaction (HER) becomes the dominant cathodic reaction. The HER drastically affects crevice propagation and leads to the formation of titanium hydride (TiHx) phases. Such phases are responsible for Ti-2 hydrogen embrittlement by decreasing Ti ductility, leaving it susceptible to hydrogen-induced cracking under tensile stress even after cessation of crevice corrosion. Due to the roles of microstructural features in these processes, the hydrogen absorption and hydride formation behaviour of Ti-2 will vary on the surface and in the bulk material. Improving our understanding of the HER and hydride formation on titanium is crucial due to their importance in material failure scenarios.Iron, present as an impurity in Ti-2, has been shown to affect titanium's corrosion behaviour drastically1. Due to the formation of TixFe intermetallic particles (IMPs), iron affects crevice corrosion behaviour, HER kinetics, and hydride formation. With the much higher exchange current density of iron (io = 2.0-3.0 x 10-6 A/cm2)2,3 compared to titanium (io = 5.0-6.3 x 10-9 A/cm2)2,4, it is probable that the HER and hydride formation will preferentially occur on IMPs. Given the influence of TiHx on corrosion behaviour and the extreme applications of Ti-2, it is crucial to develop a relationship between our understanding of TiHx formation and microstructure.This research aims to develop a relationship between Fe content in Ti, the resulting microstructure, and their effect on hydride formation, leading to improved material selection criteria, alloy development, and performance. This study investigates the initiation and propagation mechanism of TiHx formation on Ti-2 over a 24-hour period. Hydrides were grown galvanostatically in a simulated crevice corrosion environment. The surface was analyzed at various time intervals using field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), focused ion beam (FIB) milling, X-ray diffraction (XRD), and time-of-flight secondary ion mass spectrometry (ToF-SIMS). By visualizing TiHx within the matrix using FE-SEM, we determined that titanium hydride formation initiates at IMPs and then the hydride grows in all directions around these sites. After reaching a depth of ~ 5 µm below the surface of the IMP, the vertical hydride growth ceases, but the hydride continues to spread laterally across the Ti grain face until it reaches full surface coverage. Under steady-state conditions, the hydride is present as a uniformly distributed layer across the surface, with a thickness of ~ 5 µm. The electrochemical potential values during the galvanostatic hydride growth process and the amount of hydride detected using XRD support the hypothesis that the hydride proliferates before reaching a limited thickness. Elemental maps obtained using ToF-SIMS validate the observation that hydrides initiate at IMPs and confirm that the features observed in FE-SEM are hydrides. Furthermore, the amount and type of hydrogen-containing species were measured to elucidate the dynamics of TiHx formation. References He X, Noël JJ, Shoesmith DW. Effects of iron content on microstructure and crevice corrosion of Grade-2 titanium. Corrosion. 2004;60(4):378-386.Trasatti S. Work function, electronegativity, and electrochemical behaviour of metals. III. Electrolytic hydrogen evolution in acid solutions. J Electroanal Chem. 1972;39(1):163-184.Abd Elhamid MH, Ateya BG, Weil KG, Pickering HW. Calculation of the Hydrogen Surface Coverage and Rate Constants of the Hydrogen Evolution Reaction from Polarization Data. J Electrochem Soc. 2000;147(6):2148.Bockris JO, Reddy AKN. Modern Electrochemistry. Plenum Press; 1970.

Interplay of Surface Hydride, Hydrogen Evolution, and Oxygen Reduction on Cu(111)

Copper is presently the material of choice for hydrogenation reactions converting CO2 or CO to hydrocarbons and oxygenates although the identity and role of adsorbed reaction intermediates remains unresolved and understudied. Accordingly, the interactions between C, O, H, and molecules comprised thereof, with different Cu surfaces, defects and applied potentials are of substantial interest. This talk will focus on the dynamic interplay between surface hydride formation, hydrogen evolution reaction (HER), and oxygen reduction reaction (ORR) on Cu(111) in perchloric acid electrolyte using electrochemical mass spectrometry (EC-MS). Voltammetric EC-MS unveils a two-stage process for surface hydride formation, with recombination to H2 occurring at specific potentials. Controlled introduction of O2 into the cell does not disrupt hydride coverage, while its recombination potential correlates with the transition from mass-transport-limited ORR kinetics to mixed control ORR kinetics. Concurrent ORR accelerates steady-state HER onset, with a sharp increase in transient H2 production upon potential stepping. Furthermore, convolved voltammetric waves suggest surface restructuring due to O2 exposure post-ORR. These findings elucidate the complex interactions between surface species and electrochemical behavior, shedding light on Cu's catalytic selectivity and the impact of O2 on its electrochemical properties.

Nanoconfined Lanthanum Hydride Nanoconfinement in Functionalized Carbon Hosts

Metal hydrides with a high hydrogen content have long been considered for materials-based hydrogen storage and but are now attracting attention as potential high-temperature superconductors.1 Recently, we showed that cryo-milling lanthanum improves hydrogen diffusion, yielding a higher hydrogen-to-metal ratio of lanthanum hydride up to LaH4.2 Another strategy for improving the thermodynamics and hydrogen desorption kinetics of metal hydrides is nanoconfinement within porous hosts.3,4 However, this has not previously been achieved for lanthanum hydride (LaHx) due to the difficulty of isolating nanoparticles of La or La-hydrides.In this work we demonstrate that LaHx can be infiltrated into two porous carbons: nitrogen-doped CMK-3 (NCMK-3) and undoped CMK-3, both with average pore size 4-5 nm. Transmission electron microscopy (TEM) images reveal that LaHx species are distributed uniformly throughout these hosts in NCMK-3 and CMK-3 with rod and spherical morphologies, respectively. X-ray absorption spectroscopy (XAS) and X-ray photoelectron microscopy (XPS) were used to probe the coordination environment of the LaHx species and composition lanthanum and nitrogen. Sieverts measurements indicate that LaHx@NCMK-3 desorbs up to 0.7 wt % hydrogen, which is higher than the non-nitrogen functionalized CMK-3 (0.5 wt%H). Density Functional Theory (DFT) and ab initio molecular dynamics (AIMD) calculations predict that host-guest interaction energies are favorable for porous carbon with pyridinic, pyrolic, or pyridonic nitrogen defects on a graphene surface, consistent with experimental data. Moreover, high-pressure experiments were conducted to understand the tunability of hydrogen content in presence of ammonia borane as a hydrogen source. These revealed that the as-prepared materials underwent an increase in H:La ratio from 1.5 to 3.0 with pressure. Our results demonstrate that nitrogen-doped nanoporous carbons can confine lanthanum hydrides, favor higher H:La ratios, and could serve as a platform for developing superconducting materials at relatively low pressures (compared with diamond anvil cells) and temperatures. -W. Guan, R. J. Helmley, V. Viswanathan Combining pressure and electrochemistry to synthesize superhydrides PNAS 2021, 118, e2110470118.Duwal, V. Stavila, C. Spataru, M. Shivanna, P. Allen, T. Elmslie, T. C. Seagle, J. Jeffries, N. Velisavljevic, J. Smith, P. Chow, Y. Xiao, Y. Meng, M. Somayazulu, P. A. Sharma Enhancement of hydrogen absorption and hypervalent metal hydride formation in lanthanum using cryogenic ball milling Phys. Rev. Mater., 2024, submitted.Stavila, S. Li, C. Dun, M. A. T. Marple, H. E. Mason, J. L. Snider, et al. Angew. Chem. Int. Ed. 2021, 60, 25815-25824.Schneemann, L. F. Wan, A. S. Lipton, Y.-S. Liu, J. L. Snider, A. A. Baker, et al. ACS Nano 2020, 14, 10294-10304.