Hydrogen Adatoms Research Articles

Multiscale functionalized graphene origami metamaterials enable programming thermoelectric performance of flexible energy harvesters

Origami engineering stands out as one of the prominent approaches for fine tuning the multiphysical properties of energy materials. Employing first-principle calculations at the nanoscale, we explore the mechano-thermoelectric properties of graphene origami metamaterials functionalized by hydrogen (H), nitrogen (N), oxygen (O), and fluorine (F) adatoms. Our computational results reveal that functionalizing carbon (C) atoms induce buckling in the pristine graphene, transitioning carbon atoms from sp2 (for pristine graphene sheet) to hybridized sp3 orbital to fold the graphene origami. The functionalized graphene origami metamaterials, adopting the Miura-ori architecture, exhibit anisotropic mechanical properties and an unprecedented negative Poisson's ratio (NPR) of up to −0.8. Non-symmetrical functionalization breaks the inherent symmetry of graphene, resulting in a robust non-zero electronic band gap. This characteristic makes the graphene origami metamaterial a compelling contender for thermoelectric applications, since they offer an electronic figure of merit that exceed 200 at room temperature (Graphene-H), surpassing that of the majority of 2D thermoelectric materials can offer. Resorting to the finite element approach, we explore the origami-based thermoelectric legs in nanogenerators at mesoscale. The folding capability of origami architectures offer tunable heat insulation in order to realize next generation of thermoelectric legs. Compared to conventional cuboid leg thermoelectric nanogenerators, thermoelectric conversion efficiency of origami metamaterials can be two orders of magnitude higher; an enhancement that is significantly governed by their folding angle. The underlying principles governing the multiphysics performance of multiscale origami-based thermoelectric materials impart novel design concepts for customizing the thermoelectric performance of shape-changing low-dimensional metamaterials and energy-related devices.

Observation of Kekulé vortices around hydrogen adatoms in graphene

Fractional charges are one of the wonders of the fractional quantum Hall effect. Such objects are also anticipated in two-dimensional hexagonal lattices under time reversal symmetry—emerging as bound states of a rotating bond texture called a Kekulé vortex. However, the physical mechanisms inducing such topological defects remain elusive, preventing experimental realization. Here, we report the observation of Kekulé vortices in the local density of states of graphene under time reversal symmetry. The vortices result from intervalley scattering on chemisorbed hydrogen adatoms. We uncover that their 2π winding is reminiscent of the Berry phase π of the massless Dirac electrons. We can also induce a Kekulé pattern without vortices by creating point scatterers such as divacancies, which break different point symmetries. Our local-probe study thus confirms point defects as versatile building blocks for Kekulé engineering of graphene’s electronic structure.

Theoretical study of CO2 hydrogenation to methanol on modified Au/In2O3 catalysts: Effects of hydrogen spillover and activation energy prediction for hydrogen transfer

With the increasing attention in environmental issues caused by CO2 emissions, methanol conversion by CO2 hydrogenation is an effective strategy to solve this existing energy dilemma. The rationale behind hydrogen spillover on methanol synthesis is unraveled via density functional theory (DFT) calculations in this work, furthermore, the activation energy of hydrogen transfer process as affected by spillover is also summarized in a general paradigm for facilitating the understanding of hydrogenation characteristics. The results demonstrate that the spillover strategy significantly facilitates the hydrogenation reaction by supplying available hydrogen adatoms. This effect is particularly pronounced during the stage when OH is formed directly at the substrate site and combines with H to produce H2O, leading to a substantial reduction in activation energy from the initial 3.74 eV to 0.78 eV. In addition, a comprehensive predictive model for the kinetic characteristics of hydrogen spillover process is established based on the machine learning algorithm and SISSO guidance. By employing the combined approach of SISSO and neural network, we have achieved a stable prediction performance for activation energy with R2 = 0.99 and RMSE = 0.07 eV. The variable of ChgFSAu is identified as the most representative factor in describing the activation energy, demonstrating a correlation coefficient of -0.60. The extended multidimensional expression of DistAu further highlights its close connection to activation energy, achieving an RMSE value of 0.41 eV. To sum up, this work elucidates the possible thoughts of catalyst design with spillover effect and gives reference for the description screening towards the chemical reactions similar to hydrogen spillover.

Catalytic selectivity of nanorippled graphene.

Experiments have shown that nanoscale ripples in a graphene membrane exhibit unexpectedly high catalytic activity with respect to hydrogen dissociation. Nonetheless, the catalytic selectivity of nanorippled graphene remains unknown, which is an equally important property for assessing a catalyst's potential and its fit-for-purpose applications. Herein, we examine the catalytic selectivity of nanorippled graphene using a model reaction of molecular hydrogen with another simple but double-bonded molecule, oxygen, and comparing the measurement results with those from splitting of hydrogen molecules. We show that although nanorippled graphene exhibits a high catalytic activity toward hydrogen dissociation, the activity for catalyzing the hydrogen-oxygen reaction is quite low, translating into a strong catalytic selectivity. The latter reaction involves the reduction of oxygen molecules by the dissociated hydrogen adatoms, which requires additional energy cost and practically determines the selectivity. In this sense, the well-established information about reactions in general of atomic hydrogen with many other species in the literature could potentially predict the selectivity of nanorippled graphene as a catalyst. Our work provides implications for the catalytic properties of nanorippled graphene, especially its selectivity. The results would be important for its extension to a wider range of reactions and for designer technologies involving hydrogen.

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.

Dynamic Behavior of Intermediate Adsorbates to Control Activity and Product Selectivity in Heterogeneous Catalysis: Methanol Decomposition on Pt/TiO2(110).

Dynamic behavior of intermediate adsorbates, such as diffusion, spillover, and reverse spillover, has a strong influence on the catalytic performance in oxide-supported metal catalysts. However, it is challenging to elucidate how the intermediate adsorbates move on the catalyst surface and find active sites to give the corresponding products. In this study, the effect of the dynamic behavior of methoxy intermediate on methanol decomposition on a Pt/TiO2(110) surface has been clarified by combination of scanning tunneling microscopy (STM), temperature-programmed desorption (TPD), and density functional theory (DFT) calculations. The methoxy intermediates were formed by the dissociative adsorption of methanol molecules on Pt nanoparticles at room temperature followed by spillover to the TiO2(110) support surface. TPD results showed that the methoxy intermediates were thermally decomposed at >350 K on the Pt sites to produce CO (dehydrogenation) and CH4 (C-O bond scission). A decrease of the Pt nanoparticle density lowered the activity for the decomposition reaction and increased the selectivity toward CH4, which indicates that the reaction is controlled by diffusion and reverse spillover of the methoxy intermediates. Time-lapse STM imaging and DFT calculations revealed that the methoxy intermediates migrate on the five-fold coordinated Ti (Ti5c) sites along the [001] or direction with the aid of hydrogen adatoms bonded to the bridging oxygens (Obr) and can move over the entire surface to seek and find active Pt sites. This work offers an in-depth understanding of the important role of intermediate adsorbate migration in the control of the catalytic performance in oxide-supported metal catalysts.

A Facile and Surfactant-Free Electrochemical Synthesis of PtIr Nanocubes towards Ammonia Electro-Oxidation

Noble metal Pt catalyst has been identified as excellent electrocatalysts for the ammonia oxidation reaction (AOR). However, Pt’s scarcity, expensiveness, and toxicity hinder its large-scale commercial application. Herein, we report a facile and surfactant-free electrochemical synthesis method for the production of PtIr nanocubes. The PtIr nanocubes were in situ synthesized on carbon paper, and no organic additives were used at any stage in the synthesis of the catalyst. The formation of PtIr nanocubes was attributed to the synergy of the electro-adsorption/desorption of O-containing species and the preferential adsorption of hydrogen adatoms on PtIr(100) with a lower surface free energy. The obtained PtIr nanocubes exhibit an outstanding specific activity (SA) value of 1.34 mA cm−2, which is 1.5 and 3.8 times higher than Pt nanocubes (0.90 mA cm−2) and PtIr nanospheres (0.35 mA cm−2), respectively. The enhanced SA of the PtIr nanocubes can be ascribed to the synergic effects of multiple factors, including the (100) sites of the PtIr nanocubes, the dehydrogenation ability of Ir with respect to ammonia molecules, the electronic effects, and the clean surface of the catalyst due to the use of a “green” synthesis method. This work provides an effective strategy for the “green” synthesis of high-efficiency Pt-based metal catalysts with controllable shapes.

Ionicity and hydrogen affinity of water layers on metals.

The ability of metal surfaces to dissociate hydrogen molecules is key to many ways that metals react to their environment. Often, the barrier to dissociation is linked to the formation of surface hydrogen adatoms. Here, we show that hydrogen can be more strongly bound to water-covered surfaces in the form of hydronium ions than as adatoms. Density functional theory reveals that the hydronium binding is proportional to the surface electronic work function. For the case of Pt(111), a particularly high work function surface, the proton affinity of adsorbed water films can be 0.4eV larger than that of the bare metal surface. This binding is large enough to make the water films susceptible to the formation of hydroxyl and hydronium ion pairs. We present evidence from scanning tunneling microscopy for the existence of hydronium ions in water films on Pt(111). This new insight into the stability of hydronium-containing water layers provides a basis for more realistic models of the chemical reactivity of water films on metals.

Role of Electronic Structure on Nitrate Reduction to Ammonium: A Periodic Journey.

Electrocatalysis is a promising approach to convert waste nitrate to ammonia and help close the nitrogen cycle. This renewably powered ammonia production process sources hydrogen from water (as opposed to methane in the thermal Haber-Bosch process) but requires a delicate balance between a catalyst's activity for the hydrogen evolution reaction (HER) and the nitrate reduction reaction (NO3RR), influencing the Faradaic efficiency (FE) and selectivity to ammonia/ammonium over other nitrogen-containing products. We measure ammonium FEs ranging from 3.6 ± 6.6% (on Ag) to 93.7 ± 0.9% (on Co) across a range of transition metals (TMs; Ti, Fe, Co, Ni, Ni0.68Cu0.32, Cu, and Ag) in buffered neutral media. To better understand these competing reaction kinetics, we develop a microkinetic model that captures the voltage-dependent nitrate rate order and illustrates its origin as competitive adsorption between nitrate and hydrogen adatoms (H*). NO3RR FE can be described via competition for electrons with the HER, decreasing sharply for TMs with a high work function and a correspondingly high HER activity (e.g., Ni). Ammonium selectivity nominally increases as the TM d-band center energy (Ed) approaches and overcomes the Fermi level (EF), but is exceptionally high for Co compared to materials with similar Ed. Density functional theory (DFT) calculations indicate Co maximizes ammonium selectivity via (1) strong nitrite binding enabling subsequent reduction and (2) promotion of nitric oxide dissociation, leading to selective reduction of the nitrogen adatom (N*) to ammonium.

Mesoporous Silica Encapsulated Platinum-Tin Intermetallic Nanoparticles Catalyze Hydrogenation with an Unprecedented 20% Pairwise Selectivity for Parahydrogen Enhanced Nuclear Magnetic Resonance.

Supported noble metals offer key advantages over homogeneous catalysts for in vivo applications of parahydrogen-based hyperpolarization. However, their performance is compromised by randomization of parahydrogen spin order resulting from rapid hydrogen adatom diffusion. The diffusion on Pt surfaces can be suppressed by introduction of Sn to form Pt-Sn intermetallic phases. Herein, an unprecedented pairwise selectivity of 19.7 ± 1.1% in the heterogeneous hydrogenation of propyne using silica encapsulated Pt-Sn intermetallic nanoparticles is reported. This high level of selectivity exceeds that of all supported metal catalysts by at least a factor of 3. Moreover, the pairwise selectivity for alkyne hydrogenation is about 2 times higher than for alkene hydrogenation, an observation attributed to the higher coverage of the former and its effect on diffusion. Lastly, PtSn@mSiO2 nanoparticles exhibited improved coking resistance, and any loss of activity is shown to be fully reversible through high-temperature oxidation-reduction cycling.

Methane dissociation mechanism on Ni–La1−xSrxScO3−α cermet for proton ceramic electrochemical devices

In this study, we investigated the methane dissociation mechanism over a Ni–La0.90Sr0.10ScO2.95 (Ni-LSS) cermet using hydrogen/deuterium (H/D) exchange with the gas phase equilibration in the framework of the H/D exchange types approach. The measurements were conducted in the temperature range of 100–450 °C at 200 Pa methane and hydrogen mixtures (5, 10, 20 and 95 mol% methane). The hydrogen heterogeneous exchange rate between methane and Ni-LSS was found to be 2 × 1011 atom. × cm−2 × s−1 at 300 °C and 200 Pa methane and hydrogen mixture (10 mol% methane) with activation barrier 0.03 ± 0.09 eV. The rate-determining step of H/D exchange between the Ni-LSS and the mixtures is supposed to be associated with the exchange between methane adsorbed species (CHx)a and hydrogen adatoms in the adsorption layer of the cermet. The methane dissociation on the cermet can lead to the formation of dimer molecules C2H6, C2H4 and C2H2 in the gas phase from (CHx)a (x = 1–3).

S = 1 antiferromagnetic electron-spin systems on hydrogenated phenalenyl-tessellation molecules for material-based quantum-computation resources

A resource state for measurement-based quantum computation is proposed using a material design of S = 1 antiferromagnetic spin chains. Specifying hydrogen adsorption positions on polymerized phenalenyl-tessellation molecules gives rise to formation of graphene zero modes that produce local S = 1 spins or S = 1/2 spins in the required order through exchange interactions. When the S = 1 antiferromagnetic Heisenberg models serve as quantum-computation resources, hydrogen adatoms inducing zero modes can also work as local electron-spin probes in nuclear spin spectroscopy, which could be used for controlling and measuring local spins.

Electrochemical Storage of Atomic Hydrogen on Single Layer Graphene.

If hydrogen can be stored and carried safely at a high density, hydrogen-fuel cells offer effective solutions for vehicles. The stable chemisorption of atomic hydrogen on single layer graphene (SLG) seems a perfect solution in this regard, with a theoretical maximum storage capacity of 7.7 wt %. However, generating hydrogenated graphene from H2 requires extreme temperatures and pressures. Alternatively, hydrogen adatoms can easily be produced under mild conditions by the electroreduction of protons in solid/liquid systems. Graphene is electrochemically inert for this reaction, but H-chemisorption on SLG can be carried out under mild conditions via a novel Pt-electrocatalyzed "spillover-surface diffusion-chemisorption" mechanism, as we demonstrate using dynamic electrochemistry and isotopic Raman spectroscopy. The apparent surface diffusion coefficient (∼10-5 cm2 s-1), capacity (∼6.6 wt %, ∼85.7% surface coverage), and stability of hydrogen adatoms on SLG at room temperature and atmospheric pressure are significant, and they are perfectly suited for applications involving stored hydrogen atoms on graphene.

Enhancement of spin-orbit coupling and magnetic scattering in hydrogenated graphene

Spin-orbit coupling (SOC) can provide essential tools to manipulate electron spins in two-dimensional materials like graphene, which is of great interest for both fundamental physics and spintronics application. In this paper, we report the low-field magnetotransport of in situ hydrogenated graphene where hydrogen atoms are attached to the graphene surface in continuous low temperature and vacuum environment. Transition from weak localization to weak antilocalization with increasing hydrogen adatom density is observed, indicating enhancing Bychkov-Rashba-type SOC in a mirror symmetry broken system. From the low-temperature saturation of phase breaking scattering rate, the existence of spin-flip scattering is identified, which corroborates the existence of magnetic moments in hydrogenated graphene.

Formation of Mobile Hydridic Defects in Zirconium Nitride Films with n-Type Semiconductor Properties

The incorporation of mobile hydridic defects was demonstrated for low-crystalline zirconium nitride (Zr3N4−δ) films deposited by radio frequency reactive sputtering under a flow of nitrogen-rich reactive gases. Extended X-ray adsorption fine structure analysis confirmed that the local coordination environment around the Zr atoms was very close to that of the orthorhombic Eu3O4 phase. Pristine Zr3N4−δ films exhibited n-type semiconductor behavior due to the presence of nitrogen vacancy donors with a carrier concentration of 1.4 × 1020 cm–3 and an electron mobility of 2.2 × 10–3 cm2 V–1 s–1 at room temperature. Electrochemical and spectroscopic measurements confirmed that Zr3N4−δ was readily hydrogenated upon exposure to H2 gas at 300 °C to form hydridic defects via electron donation to hydrogen adatoms. Hence, the hydrogenated film exhibited H– ion/electron mixed conductor behavior in a H2 atmosphere. These findings open the possibility for exploring new hydride ion conductors based on thermodynamically stable transition metal nitrides.

Improvement of Hydrogen Sensing Performances of Sol-Gel Derived Platinum Doped Tungsten Trioxide Gasochromic Films

Introduction Various hydrogen sensitive gasochromic materials, such as V2O5 [1], MoO3 [2], and Y-Mg [3], have been reported. Among them, Catalyst-loaded WO3 film has been intensively studied to apply to smart windows or optic hydrogen sensors. Although there are many fabrication methods of WO3, sol-gel method [4, 5] is relatively cost-effective, does not need a large-scale apparatus, can be operated easily, and makes it possible to fabricate metal oxide film on complex shape surface. However, the gasochromic performance and its long-term stability sensitively depends on fabrication conditions.In this study, the effect of calcination temperature on crystalline structure, chemical state and hydrogen response of Pt-loaded WO3 (Pt/WO3) fabricated by sol-gel method were evaluated. Then, degradation behaviors were tested under various conditions. Principle In the presence of hydrogen, Pt/WO3 is reduced into tungsten bronze through reactions (1) and (2). Hydrogen molecules dissociate on the surface of catalyst into hydrogen adatoms even at room temperature. Consequently, they react with WO3 through spill-over mechanism. In the recovery process, tungsten bronze is oxidized into initial WO3 by oxygen gas in air following reaction (3). With exposure to hydrogen gas, it is well known that WO3 turns into dark blue color. In this study, transmission loss is focused as a tool for evaluating the hydrogen sensing properties of tested materials. Method WO3 precursor solution was prepared by ion-exchange method. This solution was added to the Pt containing solution which was composed of H2PtCl6, ethanol, and surfactant to make molar ratio of Pt:W about 1:5. After mixing, Pt/WO3 precursor solution was spin-coated onto the quartz glass substrates at 500 rpm for 300 seconds. The film was dried for over 1 hour. Then, the films were calcined for 1 hour in air. Calcination temperature was set in the range from 250°C to 500°C. X-ray diffraction measurements of the hydrogen sensing films were performed with CuKα radiation. The accelerating voltage and current were 40 kV and 45 mA, respectively. Fig. 1 represents the experimental set-up of transmitted light intensity measurement. The fabricated Pt/WO3 film was set into a homemade gas chamber. The one end of fiber cable was coupled with 1.3 µm LED light source. The light transmitting through the film was monitored by the optical power meter. 4 vol.% H2 gas balanced with N2 gas was used as test gas in order to evaluate hydrogen sensitivity of the film. Air as recovery gas was fed into the chamber by using an air compressor. Results and Conclusions The results of XRD measurement of Pt/WO3 films calcined at various temperature are shown in Fig. 2. The broad peak around 21° appears in all results comes from the quartz glass substrate. A sharp peak appeared at 24.0° in the film calcined at 500°C. This peak indicates formation of crystalline WO3. This peak became smaller for film calcined at 400°C and disappeared below 350°C. It indicates that crystal structure of WO3 films calcined below 350°C were amorphous. On the other hand, any peak related to Pt did not appeared. It is surmised that Pt exists in the form of microcrystalline and is well dispersed in the WO3 film.Fig. 3 represents the optical transmittance changes of the fabricated Pt/WO3 films calcined at various temperature with exposure to hydrogen containing gas. The transmitted light intensity sensitively responded to hydrogen gas and immediately reached steady states. The recovery reaction by air readily proceeded. Although the sensitivity increased with increasing calcination temperature, the response speed became slower. It would be closely related to amount of Pt° formed as a result of decomposition reaction of H2PtCl6.In order to evaluate long-term stability of Pt/WO3 film in severe condition, the effect of sodium addition to Pt/WO3 film was tested. In this experiment, Pt/WO3 coated substrate covered with small NaCl salt particles was calcined at 500°C in air at 500°C for 1 hours. Fig. 4 represents the result of hydrogen sensing test of Na-doped Pt/WO3 film. No variation in optical transmittance was observed. XPS studies suggested that catalyst-poisoning compounds generated and therefore gasochromic property of the film was considerably degraded.

Atomic Sulfur Filling Oxygen Vacancies Optimizes H Absorption and Boosts the Hydrogen Evolution Reaction in Alkaline Media

AbstractThe hydrogen evolution reaction (HER) usually has sluggish kinetics in alkaline solution due to the difficulty in forming binding protons. Herein we report an electrocatalyst in which sulfur atoms are doping in the oxygen vacancies (VO) of inverse spinel NiFe2O4 (S‐NiFe2O4) to create active sites with enhanced electron transfer capability. This electrocatalyst has an ultralow overpotential of 61 mV at the current density of 10 mA cm−2 and long‐term stability of 60 h at 1.0 Acm−2 in 1.0 M KOH media. In situ Raman spectroscopy revealed that S sites adsorb hydrogen adatom (H*) and in situ form S‐H*, which favor the production of hydrogen and boosts HER in alkaline solution. DFT calculations further verified that S introduction lowered the energy barrier of H2O dissociation. Both experimental and theoretical investigations confirmed S atoms are active sites of the S‐NiFe2O4.

Atomic Sulfur Filling Oxygen Vacancies Optimizes H Absorption and Boosts the Hydrogen Evolution Reaction in Alkaline Media.

The hydrogen evolution reaction (HER) usually has sluggish kinetics in alkaline solution due to the difficulty in forming binding protons. Herein we report an electrocatalyst in which sulfur atoms are doping in the oxygen vacancies (VO ) of inverse spinel NiFe2 O4 (S-NiFe2 O4 ) to create active sites with enhanced electron transfer capability. This electrocatalyst has an ultralow overpotential of 61 mV at the current density of 10 mA cm-2 and long-term stability of 60 h at 1.0 Acm-2 in 1.0 M KOH media. In situ Raman spectroscopy revealed that S sites adsorb hydrogen adatom (H*) and in situ form S-H*, which favor the production of hydrogen and boosts HER in alkaline solution. DFT calculations further verified that S introduction lowered the energy barrier of H2 O dissociation. Both experimental and theoretical investigations confirmed S atoms are active sites of the S-NiFe2 O4 .

Guiding the design of oxidation-resistant Fe-based single atom alloy catalysts with insights from configurational space.

The high activity and selectivity of Fe-based heterogeneous catalysts toward a variety of reactions that require the breaking of strong bonds are offset in large part by their considerable instability with respect to oxidative deactivation. While it has been shown that the stability of Fe catalysts is considerably enhanced by alloying them with precious metals (even at the single-atom limit), rational design criteria for choosing such secondary metals are still missing. Since oxidative deactivation occurs due to the strong binding of oxygen to Fe and reduction by adsorbed hydrogen mitigates the deactivation, we propose here to use the binding affinity of oxygen and hydrogen adatoms as the basis for rational design. As it would also be beneficial to use cheaper secondary metals, we have scanned over a large subset of 3d-5d mid-to-late transition metal single atoms and computationally determined their effect on the oxygen and hydrogen adlayer binding as a function of chemical potential and adsorbate coverage. We further determine the underlying chemical origins that are responsible for these effects and connect them to experimentally tunable quantities. Our results reveal a reliable periodic trend wherein oxygen binding is weakened greatest as one moves right and down the periodic table. Hydrogen binding shows the same trend only at high (but relevant) coverages and otherwise tends to have its binding slightly increased in all systems. Trends with secondary metal coverage are also uncovered and connected to experimentally tunable parameters.

Hydrogenation as a source of superconductivity in two-dimensional TiB2

Using first-principles calculations based on density functional perturbation theory, we demonstrate hydrogenation-induced superconductivity in monolayer TiB2H. Hydrogen adatoms destroy the Dirac state of monolayer TiB2 and monolayer TiB2H has a high vibration frequency. Monolayer TiB2H is a phonon-mediated superconductor. Monolayer TiB2H has a predicted [Formula: see text] of 8[Formula: see text]K, which further increases under external tensile strain. Thus, this study extends our understanding of superconductivity in two-dimensional (2D) materials and its potential applications.