H-atom Adsorption Research Articles

Enhancing catalytic efficiency: InSe quantum dots’ role in hydrogen evolution reaction

This study investigates the structural, electronic, and adsorption properties of InSe quantum dots. We focus on hydrogen atom adsorption and its implications on quantum stability chemical parameters and the hydrogen evolution reaction (HER). Optimized structures reveal distinct atomic interactions post-H adsorption, affecting bond lengths, dihedral angles, and bond angles. Adsorption energies confirm spontaneous H-adsorption across various sites, highlighting preferences for specific interactions. Electronic properties analysis showcases significant shifts in energy levels, energy gaps, and chemical parameters following H-atom adsorption, indicating a transition towards more insulating states. The catalytic performance for HER is assessed through calculated free energy changes (ΔG), demonstrating superior catalytic activity. Comparison with a Pt catalyst underscores the potential of these quantum dots as efficient HER catalysts. For instance, the ΔG value decreases to 0.005 eV in InSe-quantum dots passivated with F- and H-atoms at the edges. These findings contribute to understanding the role of InSe quantum dots in enhancing the HER reaction, offering insights for potential application in electrocatalysis and energy conversion.

Hydrogen adsorption on fcc metal surfaces towards the rational design of electrode materials

The successful large-scale implementation of hydrogen as an energy vector requires high performance electrodes and catalysts made of abundant materials. Rational materials design strategies are the most efficient means of reaching this goal. Here we present a study on the adsorption of H-atoms onto fcc transition metal surfaces and propose descriptors for the rational design of electrodes and catalysts by means of correlations between fundamental properties of the materials and among other properties, their experimentally measured performance as hydrogen evolution electrodes (HEE). A large set of quantum mechanical modelling data at the DFT level was produced, covering the adsorption of H-atoms onto the most stable surfaces (100), (110) and (111) of: Ag, Au, Co, Cu, Ir, Ni, Pd, Pt and Rh. For each material and surface, a coverage dependent set of minimum energy structures was produced and chemical potentials for adsorption of H-atoms were obtained. Averaging procedures are here proposed to approach modelling to the experiments. Several correlations between the computed data and experimentally measured quantities are done to validate our methodology: surface plane dependent adsorption energies, chemical potentials and experimentally determined surface energies and work functions. We search for descriptors of catalytic activity by testing correlations between the DFT data obtained from our averaging procedures and experimental data on HEE performance. Our methodology allows us to obtain linear correlations between the adsorption energy of H-atoms and the exchange current density (i0) in a HEE, avoiding the volcano-like plots. We show that the chemical potential has limitations as a descriptor of i0 because it reaches an early plateau in terms of i0. Simple quantities obtained from database data such as the first stage electronegativity (χ) as devised by Mulliken has a strong linear correlation i0. With a quantity we denominate modified second-stage electronegativity (χ2m) we can reproduce the typical volcano plot in a correlation with i0. A theoretical and conceptual framework is presented. It shows that both χ and χ2m, that depend on the first ionization potential, second ionization potential and electron affinity of the elements can be used as descriptors in rational design of electrodes or of catalysts for hydrogen systems.

In Situ Construction of Built-In Opposite Electric Field Balanced Surface Adsorption for Hydrogen Evolution Reaction.

Achieving a balance between H-atom adsorption and binding with H2 desorption is crucial for catalyzing hydrogen evolution reaction (HER). In this study, the feasibility of designing and implementing built-in opposite electric fields (OEF) is demonstrated to enable optimal H atom adsorption and H2 desorption using the Ni3(BO3)2/Ni5P4 heterostructure as an example. Through density functional theory calculations of planar averaged potentials, it shows that opposite combinations of inward and outward electric fields can be achieved at the interface of Ni3(BO3)2/Ni5P4, leading to the optimization of the H adsorption free energy (ΔGH*) near electric neutrality (0.05eV). Based on this OEF concept, the study experimentally validated the Ni3(BO3)2/Ni5P4 system electrochemically forming Ni3(BO3)2 through cyclic voltammetry scanning of B-doped Ni5P4. The surface of Ni3(BO3)2 undergoes reconstruction, as characterized by Grazing Incidence Wide-Angle X-ray Scattering (GIWAXS) and in situ Raman spectroscopy. The resulting catalyst exhibits excellent HER activity in alkaline media, with a low overpotential of 33mV at 10mA cm-2 and stability maintained for over 360 h. Therefore, the design strategy of build-in opposite electric field enables the development of high-performance HER catalysts and presents a promising approach for electrocatalyst advancement.

Application of a Charge Plasma Tunnel FET with SiGe Pocket as an Effective Hydrogen Gas Sensor

In this article, we have investigated the potential applications of a charge plasma TFET with a source pocket (SP-CPTFET) as a hydrogen gas sensor. The Si0.6Ge0.4 source pocket and HfO2 gate dielectric together greatly enhance the drain current. The presence of an intrinsic silicon body in the channel and drain controls the leakage current. Palladium (Pd) is considered the top and bottom gate catalyst for hydrogen (H2) gas sensing. The flat band voltage and CV properties of the sensor change as a result of the adsorption of H-atoms at the Pd-HfO2 and Pd surfaces. As a result, the gate work-function () modulates, affecting the drain current. The electrical analysis of the sensor is carried out in terms of transfer characteristics, band energy, current ratio, interband tunneling rate, and electric field. Additionally, the suggested sensor’s drain current sensitivity and current ratio sensitivity are estimated for various H2 pressure concentrations. The scope of the investigation has been expanded to include the effect of variation in the H2 gas pressure, germanium mole fraction, temperature, pocket length, interface trap charges (ITC), oxide thickness variation, and comparison of different catalytic metals on the drain current performance. The reported sensor exhibits a much-improved drain current sensitivity and current ratio sensitivity compared to the CPTFET gas sensor.

Porous CeO2/Ni-Cu composite catalyst for electrocatalytic hydrogen evolution in alkaline medium

High-efficiency low-cost and long-term stable hydrogen evolution catalysts play a decisive role in the production of hydrogen energy. Different from many previous studies that use binder to adhere nanoparticles to electrode substates CeO2 nanoparticles are successfully introduced to a porous Ni-Cu substrate without binders in this work. The CeO2-modified Ni-Cu catalyst has abundant active sites which can promote the mass transfer and facilitate the Hatom adsorption of hydrogen evolution reaction. In addition the oxygen vacancies of CeO2 and the synergistic effect between Ce3+ and Ce4+ are manifested during the hydrogen evolution reaction. For producing hydrogen through water electrolysis results show that the obtained porous CeO2/Ni-Cu catalyst presents an overpotential of 72 mV at a current density of 10 mA·cm−2 as well as a long-term stability of more than 24 h. This work provides new idea for the development of the composite catalyst derived from non-precious metals with the stable structure for hydrogen evolution reaction in alkaline condition.

Tweaking Nickel with Minimal Silver in a Heterogeneous Alloy of Decahedral Geometry to Deliver Platinum‐like Hydrogen Evolution Activity

Five-fold intertwined Agx Ni1-x (x=0.01-0.25) heterogeneous alloy nanocrystal (NC) catalysts, prepared through unique reagent combinations, are presented. With only ca. 5 at % Ag (AgNi-5), Pt-like activity has been achieved at pH 14. To reach a current density of 10 mA cm-2 the extremely stable AgNi-5 requires an overpotential of 24.0±1.2 mV as compared to 20.1±0.8 mV for 20 % Pt/C, both with equal catalyst loading of 1.32 mg cm-2 . The turnover frequency (TOF) is as high as 2.1 H2 s-1 at 50 mV (vs. RHE). Site-specific elemental analyses show the Ag:Ni compositional variation, where the apex and edges of the decahedra are Ag-rich, thereby exposing Ni onto the faces to achieve maximum charge transport for an exceptional pH universal HER activity. DFT calculations elucidate the relative H-atom adsorption capability of the Ni centers as a function of their proximity to Ag atom.

Tunable band gap and enhanced ferromagnetism by surface adsorption in monolayer Cr2Ge2Te6

Two-dimensional (2D) van der Waals (vdW) materials have attracted significant attention for their promising applications in spintronic devices. Here, using first-principles calculations and renormalized spin-wave theory, we investigate the influence of surface adsorption (H and alkali metals) on the bandgap and ferromagnetism of monolayer ${\mathrm{Cr}}_{2}{\mathrm{Ge}}_{2}{\mathrm{Te}}_{6}$. We find that H-atom adsorption maintains the bandgap of ${\mathrm{Cr}}_{2}{\mathrm{Ge}}_{2}{\mathrm{Te}}_{6}$ around 0.95 eV but leads to a nearly indirect-to-direct band gap transition, while alkali-metal adsorption removes the bandgap and induces metallicity. More importantly, both H and alkali-metal adsorption surprisingly make the magnetic anisotropy energy four times larger than that of pristine ${\mathrm{Cr}}_{2}{\mathrm{Ge}}_{2}{\mathrm{Te}}_{6}$, leading to an increase of ${T}_{\mathrm{c}}$ by about 33%. Our findings of adsorption-controlled bandgap and magnetism in a 2D vdW magnet may open up opportunities for potential applications for new-generation magnetic memory storage, sensors, and spintronics.

Evaluation of H-atom adsorption on wall surfaces with a plasma molecular beam scattering technique

Toward a precise modeling for wall chemical effects in flame-wall interactions, radical adsorption on different wall surfaces are directly evaluated through a newly-developed molecular beam scattering technique using a non-equilibrium plasma–driven beam source as well as an ultra-high vacuum chamber. Firstly, sensitivities of adsorption rates for each radical species to the wall chemical effect are examined through a series of numerical simulations with detailed gas/surface chemistry for a methane-air premixed flame. Since H-atom has a higher diffusivity and its adsorption significantly inhibits a chain branching reaction of H + O2 = O + OH, H is considered to be the most influential radical on the flame characteristics such as heat release rate or CO emission if compared to OH, O and CH3. Based on the sensitivity analysis, H adsorptions are quantified for quartz and SUS321 surfaces with the plasma molecular beam scattering measurements. It is confirmed that H atomic beam can be successfully produced through the plasma dissociation of H2 molecules. Then, the produced H beam is irradiated onto quartz and SUS321 surfaces at different wall temperatures Tw. It is found that H is adsorbed on the quartz and SUS321 surfaces, and reaction probabilities of H PH has its maxima at Tw ∼673 K for both surfaces. This is probably because that the recombination rate increases as Tw increases, while the desorption rate is also promoted and overcomes the recombination rate at Tw > 673 K. The PH for the SUS321 is in agreement with that in our previous combustion experiments and more precise value can be obtained by the present method.

Electronic structure tuning during facile construction of two-phase tungsten based electrocatalyst for hydrogen evolution reaction

Fabrication of effective electrocatalysts combining two pure phases including carbide and phosphide with a certain proportion by the clean and simple strategies still remain a challenge. Here we synthesized tungsten carbide/tungsten phosphide-coated N-doped carbon (W2C/WP@NC) by one-step pyrolysis process without participation of PH3. In this synthesis process phosphotungstic acid, a heteropolyacid provided P and W atoms while 2,6-diaminopyridine, a heterocyclic compound with strong alkalinity acted as C and N source. 2,6-diaminopyridine was carefully chosen because it made a contribution to the complete decomposition of phosphotungstic acid where WO42− and PO43− groups were formed which both were essential to formation of WP phases. An overpotential of 83 mV which was required to achieve a current density of 10 mA cm−2 in 0.5 M H2SO4 exhibited the high electrocatalytic activity of W2C/WP@NC catalyst in hydrogen evolution reaction (HER). The weight ratio of W2C to WP was calculated by Rietveld refinement and near edge X-ray absorption fine structure (XANES). W L3-edge XANES spectra of different samples confirmed that little amount of WP could tune the electron state on W species. The enhanced HER performance was attributed to the favorable electron distribution on W species in W2C/WP@NC which approached to the balance between H-atom adsorption and desorption.

Endohedral metallofullerenes (M@C60) as efficient catalysts for highly active hydrogen evolution reaction

The cage structure of C60 fullerenes with encapsulated metal atoms, i.e. endohedral fullerenes (M@C60) possess unique electronic properties with novel applications. By using density functional theory (DFT), we for the first time predict endohedral M@C60 (M=Na, K, Rb, Cs, Sc, Ti, Mn, Fe) fullerenes from 20 possible candidates as promising high performance hydrogen evolution reaction (HER) catalysts. For the pristine C60, the Gibbs free energy is too positive to prevent the adsorption of H-atoms on surface carbon atoms. However, when a metal atom is embedded in the C60 cage, the H-atom binding free energy on M@C60 can be optimized to ideal value for HER (ΔGH=0). The catalytic active site is non-metal C-atom and the HER performance of M@C60 are even better than those of the state-of-the-art Pt and MoS2 catalysts. The excellent catalytic activities are attributed to the charge transfer between the metal atom and C60 cage. Since the endohedral fullerenes can be easily realized in experiment, our findings highlight a new class of low-cost and efficient HER catalyst for experimental validation studies toward hydrogen production.

Efficient Catalysis of Hydrogen Evolution Reaction from WS2(1-x) P2x Nanoribbons.

The rational design of Earth abundant electrocatalysts for efficiently catalyzing hydrogen evolution reaction (HER) is believed to lead to the generation of carbon neutral energy carrier. Owing to their fascinating chemical and physical properties, transition metal dichalcogenides (TMDs) are widely studied for this purpose. Of particular note is that doping by foreign atom can bring the advent of electronic perturbation, which affects the intrinsic catalytic property. Hence, through doping, the catalytic activity of such materials could be boosted. A rational synthesis approach that enables phosphorous atom to be doped into WS2 without inducing phase impurity to form WS2(1-x) P2x nanoribbon (NRs) is herein reported. It is found that the WS2(1-x) P2x NRs exhibit considerably enhanced HER performance, requiring only -98 mV versus reversible hydrogen electrode to achieve a current density of -10 mA cm-2 . Such a high performance can be attributed to the ease of H-atom adsorption and desorption due to intrinsically tuned WS2 , and partial formation of NRs, a morphology wherein the exposure of active edges is more pronounced. This finding can provide a fertile ground for subsequent works aiming at tuning intrinsic catalytic activity of TMDs.

The effect of chemoinduced emf in CdTe films upon its interaction with atomic hydrogen

The effects of excitation of the transverse chemovoltage (chemo-emf) and nonequilibrium chemoconductivity in a CdTe film obtained by the “oblique deposition” method upon its interaction with atomic hydrogen are studied. Both effects are related to the nonthermal generation of electron-hole pairs in the semiconductor film caused by the energy released in chemical events of interaction between H atoms and the CdTe surface (the adsorption of atoms and formation of H2 molecules). The chemovoltage and chemoconductivity kinetics and the dependence of the steady-state values of the effects on the atomic-flux density and sample temperature are studied. It is established that the events of both H-atom adsorption and their recombination participate in the process of (e−h) pair generation. Analytical expressions for the chemovoltage and chemoconductivity are obtained. The numerical values of the parameters of interaction between H atoms and the CdTe surface and the effectiveness of (e−h) pair generation are estimated.

The effect of alloying on the H-atom adsorption on the (100) surfaces of Pd-Ag, Pd-Pt, Pd-Au, Pt-Ag, and Pt-Au. A theoretical study

Abstract The effect of alloying on the adsorption of atomic hydrogen was studied using density functional theory (DFT). In the study the (100) surfaces of Pd-Ag, Pd-Pt, Pd-Au, Pt-Ag, and Pt-Au alloys were considered by means of a cluster model. The structural and energetic properties of the H atom adsorbed on the Pd4Me (Me = Ag, Pt, Au) and Pt4Me (Me = Pd, Ag, Au) clusters were calculated and compared with the H-atom adsorption on monometallic clusters. The effect of alloying on the H-atom adsorption is evident for all the investigated bimetallic systems. However, it strongly depends on the second metal atom, Me, is placed in the surface layer or in the subsurface one. In general, the H atom adsorbed in a site containing the second metal exhibits different properties from those characteristic of its adsorption on Pd(100) and Pt(100). Hence, the modified interaction between atomic hydrogen and the alloyed surfaces may increase the selectivity of the catalytic hydrogenation reactions on such surfaces.

Electronic excitation in atomic adsorption on metals: A comparison of ab initio and model calculations

Results of calculations using time-dependent density functional theory and an analytic solution of the mean-field Newns–Anderson model are compared for the spectrum of electronic excitations generated by the adsorption of H-atoms on the Al(1 1 1) surface. It is shown that the main features of the spectra as a function of the incident energy of the H atoms are similar, but some details are not in quantitative agreement.

First-Principles Calculations of M<SUB>10</SUB>/Graphene (M = Au, Pt) Systems —Atomic Structures and Hydrogen Adsorption—

The usage of Au nano-particles as a catalytic electrode may be effective for the CO-poisoning problem in the anode of a proton-exchange membrane fuel cell (PEMFC), because Au nano-particles supported on metal oxides have novel catalytic activity of low-temperature CO oxidation or water gas-shift reaction. As the first step to examine this possibility, we have performed first-principles calculations of a Au 10 cluster on graphene as well as a Pt 10 cluster on graphene, based on the density functional theory (DFT). There are no strong interactions between the cluster and graphene such as substantial charge transfer or orbital hybridization, although the interaction for Pt is stronger than that for Au. We have further examined the H-atom adsorption on the clusters on graphene, and found that the adsorption energy is much larger for the Pt cluster than for the Au cluster. However, we have observed that the energy gain in the dissociation and adsorption from a H 2 molecule is indeed obtained for the Au small cluster in spite of no energy gain for the Au (111) surface.

Hydrogen-Adsorption Induced Atomic Rearrangement of a Pb Monolayer on Si(111)

We have observed interesting H-atom adsorption induced atomic rearrangements of a Pb monolayer on the Si(111) with a scanning tunneling microscope. A hexagonal ringlike pattern is formed around the point defect. The interactions among nearby H-adsorbed defects can even produce interferencelike superstructures. Phase boundaries are found to either enhance or suppress the formation of the interference pattern. These phenomena are produced by an intricate interplay between electronic and atomic interactions as perturbed by the adsorbed hydrogen atoms.

Interaction of hydrogen with metal oxides: the case of the polar ZnO(0 0 0 1) surface

The formation and structure of hydrogen adlayers on the Zn-terminated ZnO(0 0 0 1) surface have been investigated by various analytical techniques. Whereas low energy electron diffraction data showed virtually no change upon H-atom adsorption, the highly surface sensitive method of He-atom scattering revealed for small H-coverages the formation of a H(1×1) overlayer. Surprisingly, for larger exposures to hydrogen (both atomic and molecular) the surface becomes highly unstable. Even before completion of the H(1×1) overlayer the polar Zn–ZnO-surface restructures, most likely as a consequence of subsurface OH-formation. The defects formed in this restructuring process are found to strongly increase the sticking coefficient of hydrogen molecules.

Interaction of atomic hydrogen with potassium on MgO(100)

The adsorption of potassium and its interaction with hydrogen atoms on MgO(100) have been studied by thermal desorption spectroscopy (TDS). The desorption energy of adsorbed K atoms was found to decrease from 82.3 to 78.5 kJ mol−1 with increasing potassium coverage in the range of θK ≤ 1ML, which is attributed to the repulsive dipole interaction between adsorbed K atoms. At θK < 1ML, H-atoms are adsorbed and bound to the K adatoms on MgO(100), forming the HKO species. On multilayer K-covered surfaces, two hydrogen desorption peaks, α and α′, were observed due to the thermal decomposition of two possible bulk hydrides formed beneath the surface. The β peak in hydrogen desorption is probably related to the surface-adsorbed hydrogen species. In addition, hydrogen diffusion into the bulk during H-atom adsorption or thermal annealing has been observed.

A semiempirical quantum chemistry approach to possible structures and energies of hydrogen atoms adsorbed on Pt(100) and Pt(111) clusters at a simulated Pt/aqueous electrochemical interface

Extended Hueckel molecular orbital calculations for the adsorption of H-atoms in a simulated aqueous electrochemical environment on Pt(111) and Pt(100) clusters were made. Different adsorbate configurations were considered. H-atom adsorption on hollow sites coadsorbed with an on top OH-species for Pt(111), and H-atom adsorption on bridge sites for Pt(100) are favoured. At potentials lower than the hydrogen electrode equilibrium potential, H-adatom configurations involving subsurface Pt atoms can also be formed. For both Pt(111) and Pt(100), these structures are probably related to species involved in the H-atom electrosorption and hydrogen evolution reaction.

Enhanced metal depletions and interstellar H2 abundances

THE OAO 3 Copernicus ultraviolet satellite has provided important new data on the abundances of elements in the interstellar gas in the direction of many O and B-stars along lines of sight of low optical depth1–4. This information may make it possible to choose between the following theories of molecular hydrogen formation in interstellar clouds: (1) physical adsorption of H-atoms on to cold dielectric grains and their subsequent recombination and desorption5; (2) H2 recombination on graphite grains6; and (3) hydrogen recombination by non-activated chemisorption on transition metal grains7. Indirect methods of testing the above theories are essential because there is a glaring lack of experimental data, especially for processes (1) and (2). Also, it does not seem possible that in the near future radio astronomers will be able to measure the abundances of the various hydrogen ions (such as H2+ and H3+) that the above theories predict8.