Hydrogen Adsorption Research Articles

Cation vacancy modulated Cu3P-CoP heterostructure electrocatalyst for boosting hydrogen evolution at high current densities and coupling Zn-H2O battery

Exploiting highly efficient, cost-effective and stable electrocatalysts is key to decreasing hydrogen evolution reaction (HER) kinetics energy barrier. Herein, the alkaline HER kinetics energy barrier can greatly reduce by the joint strategies of the cation vacancy and heterostructure engineering, which is seldom explored and remains ambiguous. In this study, an efficient and stable copper foam-supported Cu3P-CoP heterostructure electrocatalyst with cation vacancy defects (defined as Cu3P-CoP-VAl/CF) was designed for HER via the successive coprecipitation, electrodeposition, alkali etching and phosphorization treatments. As anticipated, the as-obtained Cu3P-CoP-VAl/CF electrocatalyst reveals a remarkable catalytic activity for HER with a low overpotential of 205 mV at a current density of 100 mA·cm−2, a high turnover frequency value of 1.05 s−1 at an overpotential of 200 mV and a small apparent activation energy (Ea) of 9 kJ·mol−1, while shows superior long-term stability at large current densities of 100 and 240 mA·cm−2. Systematic experiment and characterization data demonstrate that the formed cation vacancy could optimize the Ea, leading to the decrease of the kinetic barriers of Cu3P-CoP/CF heterostructure, as well as the established heterogeneous interface induced a synergistic effect between biphasic components on boosting the kinetics toward HER. The results of density functional theory disclose that the synergistic effect of Cu3P-CoP heterostructure could decrease the energy barrier and optimize Gibbs free energy of hydrogen adsorption, resulting in the enhancement of intrinsic catalytic activity of Cu3P-CoP-VAl/CF. More significantly, the alkali-cell assembled by Cu3P-CoP-VAl/CF (cathode) and RuO2/CF (anode) behaves outstanding water splitting performance, delivering a current density of 10 mA·cm−2 at a relatively small applied voltage of 1.58 V, along with encouraging long-term durability. In addition, the alkaline Zn-H2O battery with Cu3P-CoP-VAl/CF as the cathode has been fabricated for the simultaneous generation of electricity and hydrogen, which displays a large power density of up to 4.1 mW·cm−2. The work demonstrates that rational strategy for the design of competent electrocatalysts can effectively accelerate the kinetics of HER, which supplies valuable insights for practical applications in overall water splitting.

Enhancing hydrogen adsorption through optimized magnesium dispersion on fibrous nano-silica scaffold: Kinetic and thermodynamic studies

Silica material, particularly, fibrous nano-silica (FNS) is one of the potential scaffolds for hydrogen storage, however, low hydrogen adsorption limits its application. To improve its adsorption capacities, the incorporation of active metal, particularly magnesium (Mg), was prepared. FNS with well-developed pore structures and a good surface area were synthesized. Various amounts of Mg (1–5 wt%) were infiltrated into the FNS. To study the effect of metal loading, the adsorbents were characterized by their chemical structure, crystal phase, morphology/elemental composition, and textural properties. Subsequently, hydrogen adsorption studies were conducted where different reaction conditions, including metal loading, catalyst loading, and temperature were studied. Furthermore, kinetic and thermodynamic studies were conducted based on the Langmuir and Van't Hoff models. The results of the characterizations show that the Mg metal was well dispersed into the porous FNS with no significant changes in the original structure. The optimum adsorption of 1.90 wt% was achieved at 1.0 wt% Mg loading, 0.1 g catalyst loading, and 423 K temperature. Kinetic studies demonstrated that the adsorption process fits the pseudo-second-order reaction. The 1%Mg/FNS adsorbents showed good reusability where 5 runs were conducted with <5 % loss in activity. Therefore, this result indicated that infiltration of Mg into the silica is one of the most active approaches in improving the hydrogen adsorption capacities of FNS.

Optimizing hydrogen permeation properties of WS2-Ni composite coatings on pipeline steel for improved hydrogen protection

Tungsten disulfide (WS2) has broad applications due to its unique molecular structure and outstanding physicochemical properties. In particular, the physical barrier properties of WS2 make it suitable to act as barriers against hydrogen. Herein, WS2-Ni composite coatings are prepared by electrodeposition to mitigate hydrogen-induced damage of X70 pipeline steel. The influence of the WS2 concentration on the hydrogen resistance of coating is assessed by electrochemical hydrogen permeation test, hydrogen adsorption simulation, slow strain rate tensile test (SSRT), and fracture analysis. As the WS2 concentration increases, the distributions of WS2 in the coatings transition from sparse to uniform and then agglomeration, while the grain size of Ni decreases initially and then decreases. These microstructural changes impact the hydrogen adsorption sites and diffusion paths, leading to a non-linear relationship between the hydrogen permeation resistance and WS2 concentration. This similar concentration dependence is also observed from the hydrogen embrittlement (HE) resistance of coatings, suggesting that enhancing the hydrogen permeation resistance can improve the HE resistance. This study highlights the great potential of WS2 as an effective barrier against hydrogen permeation, and the results provide insights into the hydrogen protection mechanism of pipeline steel.

Indirect determination of free chlorine in seawater by cyclic voltammetry using graphite–epoxy composite electrode: Hydrogen adsorption capacity of graphite–epoxy composite is one–third of that of platinum

A new possibility of indirect determination of free chlorine using a graphite–epoxy composite(GEC) electrode instead of Pt disk electrode was suggested by interpreting the relationship between the peak current of the oxidation peak for hydrogen generated through water electrolysis in CV and the amount of the free chlorine. The linear response range of concentration was 0.06–0.2 mg∙L−1 with correlation coefficient of 0.9951 (n = 5) and the sensitivity of 1225 μA cm−2 mg−1 L. The limit of detection (LOD) calculated from the 3σ IUPAC criteria was 1.2 × 10−2 mg L−1. The relative standard deviation (RSD) to 0.06 mg L−1 was 4.65%(n = 10). The results show that the amount of free chlorine in the disinfected seawater can be indirectly determined by using a GEC electrode without influence of interferences unlike a Pt disk electrode. On the other hand, in this paper, a new method is proposed to evaluate the relative hydrogen adsorption capacity by the sensitivity of GEC electrode compared with that of Pt disk electrode. During the investigation of the hydrogen adsorption on the surface of the working electrode, we obtained the result that the hydrogen adsorption capacity of GEC is one-third of that of platinum.

Constructing the synergistic active sites of nickel bicarbonate supported Pt hierarchical nanostructure for efficient hydrogen evolution reaction

Constructing synergistic active sites and optimizing the cooperative adsorption energies for hydrogen and hydroxyl based intermediates are two essential strategies to improve the sluggish kinetics of hydrogen evolution reaction (HER) in alkaline medium. However, it is still in its infancy to simultaneously achieve these goals, especially for designing a well-defined carrier with multiple hydroxyl adsorption sites. Herein, the Ni(HCO3)2 nanoplates (NHC) with horizontal interfaces sites of Ni-terminated NiO, NiOOH, NiCOO, and Ni(OH)2 were employed as the hydroxyl adsorption active sites, which could anchor Pt particles with hydrogen adsorption active sites, constructing the synergistic active sites (NHC-Pt) for HER catalysis. Evidenced by X-ray photoelectron spectroscopy (XPS) and extended X-ray absorption fine structure (EXAFS), the NHC could affect the chemical state and electronic structure of Pt particles by forming bond of Pt-O which could reduce the reaction energy barriers, facilitate the adsorption of hydrogen and establishment of H–H bond. Furthermore, density functional theory (DFT) theoretical calculation revealed that the related process of hydroxide was the rate-determining step. It is demonstrated the hydroxyl group presents the lowest energy barrier for desorption in the process of HER when the gradual desorption process could be described as a migration from Ni(HCO3)2·OH directly or via other Ni-based systems formed after partial decomposition of nickel hydrocarbonate to Ni(OH)2···OH with following desorption. As a result, the NHC-Pt hierarchical nanostructure demonstrated superior activity towards HER in a pH-universal solution. This enhancement can be attributed to the optimized electronic structure of Pt, the migration of hydroxyl group on NHC substrates, and the synergistic effects between the NHC carrier and Pt particles.

Hydrogen adsorption and dissociation, together with a multifractal transition into graphene-based surfaces

Ab-initio molecular dynamics simulations, together with multifractal detrended fluctuation analysis (MF-DFA) were used to study hydrogen adsorption into a five-vacancy graphene surface. This surface was chosen because it presents active bonds, due to a lack of carbon ions and may thus be appropriate for molecular hydrogen adsorption and storage. Hydrogen dissociation and chemical hydrogen adsorption, together with a multifractal transition were observed at the beginning of molecular dynamics simulations. Multifractal phase transition is a consequence of hydrogen dissociation and adsorption and was observed in the multifractal spectrum, as a fishtail-like behavior. Once the molecular hydrogen was adsorbed and dissociated, a weak multifractal spectrum was observed in time-series. Weak multifractal behavior was adduced by comparing to fractional Brownian motion (FBM). Multifractal characterization indicates irregular signals and anti-persistence, caused by temperature. A fractional Brownian motion region for forecasting and benchmarking, based on statistical indicators and multifractal characterization of the test region is proposed. The results obtained in this investigation may be significant in the search for surfaces and strategies for hydrogen storage.

Synthesis of polymetallic oxide nanoarrays as efficient hydrogen evolution reaction electrocatalyst for alkaline seawater and urea splitting

Nowadays, with the depletion of traditional fossil resources, hydrogen energy comes into our eyes as a renewable and sustainable energy source. Electrocatalytic water splitting has been widely studied as an environmentally friendly method to produce hydrogen rapidly and large-scale. Since 96.5 % of the world’s abundant water resources are seawater, exploring an economical and efficient catalyst for seawater splitting is an attractive method to realize industrial hydrogen production. In this paper, polymetallic oxide Mn-MoWNi catalyst was in situ synthesized on nickel foam using one-step hydrothermal approach and composite strategy. The catalyst has excellent hydrogen evolution reaction (HER) performance in seawater and urea solution containing 1 M KOH. In 1 M KOH alkaline seawater solution, Mn-MoWNi only requires overpotential of 261 mV to drive the current density of 100 mA cm−2. When the current density of 100 mA cm−2 was reached in the alkaline solution of 1 M KOH + 0.5 M Urea, the overpotential of Mn-MoWNi catalyst was only 206 mV. After 15 h stability measurement in 1 M KOH alkaline seawater solution, the surface morphology of Mn-MoWNi was changed and corroded, indicating that its stability needs to be improved. Density functional theory calculations show that in Mn-MoWNi catalysts, MoO3 promotes the hydrogen adsorption ability of the material, while MnO2 promotes the electrical conductivity of the electrode, and both of them work synergistically with WO3 and NiWO4 to jointly improve the activity of the catalyst.

Lattice Strain with Stabilized Oxygen Vacancies Boosts Ceria for Robust Alkaline Hydrogen Evolution Outperforming Benchmark Pt.

Earth-abundant metal oxides are usually considered as stable but catalytically inert toward hydrogen evolution reaction (HER) due to their unfavorable hydrogen intermediate adsorption performance. Herein, a heavy rare earth (Y) and transition metal (Co) dual-doping induced lattice strain and oxygen vacancy stabilization strategy is proposed to boost CeO2 toward robust alkaline HER. The induced lattice compression and increased oxygen vacancy (Ov) concentration in CeO2 synergistically improve the water dissociation on Ovsites and sequential hydrogen adsorption at activated Ov-neighboring sites, leading to significantly enhanced HER kinetics. Meanwhile, Y doping offers stabilization effect on Ov by its stronger Y─O bonding over Ce─O, which endows the catalyst with excellent stability. The Y,Co-CeO2 electrocatalyst exhibits an ultra-low HER overpotential (27mV at 10mA cm-2) and Tafel slope (48mV dec-1), outperforming the benchmark Pt electrocatalyst. Moreover, the anion exchange membrane water electrolyzer incorporated with Y,Co-CeO2 achieves excellent stability of 500h under 600mA cm-2. This synergistic lattice strain and oxygen vacancy stabilization strategy sheds new light on the rational development of efficient and stable oxide-based HER electrocatalysts.

Electronic, magnetic and catalytic of the Janus monolayer transition-metal trichalcogenides

Nowadays, a booming research direction goes toward the newly two-dimensional (2D) layered materials known as metal phosphorus trichalcogenides, which have intrinsic magnetism. Janus 2D materials with mirror asymmetry display novel properties, providing great promise for application in sensors, catalysis, and electronics devices. Herein, the magnetic, electronic as well as the catalytic properties of Janus MPS1.5Se1.5 (M = Mn, Fe, Ni) monolayer trichalcogenides are systematically studied based on the first-principles calculations. We find that all the three Janus MPS1.5Se1.5 possess antiferromagnetic order, however with different antiferromagnetic configurations. Strain-driven magnetic phase transitions are found in FePS1.5Se1.5. Electronic calculations reveal that all the Janus MPS1.5Se1.5 (M = Mn, Fe, Ni) are semiconductors and the band gaps can be tuned by biaxial strain. We further show that the Janus FePS1.5Se1.5 with optima hydrogen adsorption free energy and good conductivity may be potential candidate for HER electrocatalyst.

Tailoring Hydrogen Evolution Reaction with single-atom catalysts on Ti[formula omitted]B MBenes: Insights from computational screening

The utilization of single-atom catalysts (SACs) in the context of the Hydrogen Evolution Reaction (HER) holds significant promise for advancing electrocatalysis. Upon implantation or anchoring on two-dimensional (2D) materials, these catalysts exhibit improved stability, selectivity, and reactivity. This study uses density functional theory-based computational techniques to demonstrate the potential of SACs embedded on novel 2D materials, such as MBenes. To assess their HER activity, the transition metals (TMs) are screened as SACs embedded in Ti2B monolayer. Our results indicate that the inclusion of a single TM can finely adjust hydrogen adsorption, resulting in a characteristic volcano-like pattern, and particularly Pd-Ti2B emerges as a standout candidate, with an optimal Gibbs free energy of −0.057 eV. Moreover, Pd-Ti2B exhibits a notable exchange current density of 1.25 × 10−4 Acm−2 surpassing that of numerous traditional metal catalysts, including Pt(111), by approximately 105%. Furthermore, we underscore the electronic characteristics contributing to the extraordinary electrocatalytic activity of a single TM atom encased in Ti2B, viz., Pd-Ti2B, for HER. This study contributes greatly to our understanding of electrocatalytic processes and facilitates the development of potent MBenes-based catalysts for hydrogen evolution.

Discovery of Self-Assembled 2D Ru/Si Superlattices Boosting Hydrogen Evolution.

2D heterostructuring is a versatile methodology for designing nanoarchitecture catalytic systems that allow for reconstruction and modulation of interfaces and electronic structures. However, catalysts with such structures are extremely scarce due to limited synthetic strategies. Here, a highly ordered 2D Ru/Si/Ru/Si… nano-heterostructures (RSHS) is reported by acid etching of the LaRuSi electride. RSHS shows a superior electrocatalytic activity for hydrogen evolution with an overpotential of 14mV at 10mA cm-2 in alkaline media. Both experimental analyses and first-principles calculations demonstrate that the electronic states of Ru can be tuned by strong interactions of the interfacial Ru-Si, leading to an optimized hydrogen adsorption energy. Moreover, due to the synergistic effect of Ru and Si, the energy barrier of water dissociation is significantly reduced. The well-organized superlattice structure will provide a paradigm for construction of efficient catalysts with tunable electronic states and dual active sites.

Phosphorous Vacancy and Built-In Electric Field Effect of Co-Doped MoP@MXene Heterostructures to Tune Catalytic Activity for Efficient Overall Water Splitting.

Developing cost-effective, durable bifunctional electrocatalysts is crucial but remains challenging due to slow hydrogen/oxygen evolution reaction (HER/OER) kinetics in water electrolysis. Herein, a combined engineering strategy of phosphorous vacancy (Vp) and spontaneous built-in electric field (BIEF) is proposed to design novel highly-conductive Co-doped MoP@MXene heterostructures with phosphorous vacancy (Vp-Co-MoP@MXene). Wherein, Co doping regulates the surface electronic structure and charge re-distribution of MoP, Vp induces more defects and active sites, while BIEF accelerates the interfacial charge transfer rate between Vp-Co-MoP and MXene. Therefore, the synergistic integration of Vp-Co-MoP/MXene efficiently decreases activation energy and kinetic barrier, thus promoting its intrinsically catalytic activity and structural stability. Consequently, the Vp-Co-MoP@MXene catalyst displays low overpotentials of 102.3/196.5 and 265.0/320.0mV at 10/50mA cm-2 for HER and OER, respectively. Notably, two-electrode electrolyzers with the Vp-Co-MoP@MXene bifunctional catalysts to achieve 10/50mA cm-2, only need low-cell voltages of 1.57/1.64V in alkaline media. Besides, experimental and theoretical results confirm that the hetero-structure effectively reduces hydrogen adsorption free energy and rate-determining-step energy barrier of OER intermediates, thereby greatly boosting its intrinsically catalytic activity. This work verifies an effective strategy to fabricate efficient non-precious bifunctional electro-catalysts for water splitting via combination engineering of phosphorous vacancy, cation doping, and BIEF.

Enhanced acidic hydrogen evolution reaction kinetics via nitrogen-doped iridium nanosheet with optimized hydrogen adsorption energy

The hydrogen evolution reaction (HER) is influenced by the adsorption/desorption of hydrogen intermediates on active sites. Nitrogen doping is a way to alter the electronic structure and boost the activity of metal electrocatalysts although the mechanism remains controversial. Here, nitrogen is incorporated into face-centered cubic iridium nanosheets (N-fcc-Ir-NSs) through the ammonia reduction of metastable two-dimensional pristine trigonal iridium oxide. With a nitrogen content of only 0.8 wt%, N-fcc-Ir-NSs exhibit a low overpotential of 19 mV at −10 mA cmgeo-2 and a Tafel slope of 18.6 mV dec-1 in sulfuric acid. The doped nitrogen reduces hydrogen adsorption energy by modulating the electronic structure of iridium atoms, and the combined effects of iridium sites with strong hydrogen adsorption energy and iridium sites near the nitrogen atoms with weak hydrogen adsorption energy improve the HER activity. Moreover, the presence of nitrogen causes iridium to donate more electrons to hydrogen and promotes hydrogen desorption.

Coordinated Adsorption/Desorption Kinetics Enabled by Surface Sulfur Decoration Over Mo2C for Boosted Hydrogen Evolution Reaction

AbstractMaintaining a consistently high current density growth rate in the hydrogen evolution reaction is highly challenging because the limited mass transfer rate at the electrode/electrolyte interface will make the adsorption reaction as the rate‐determining step associated with a low hydrogen coverage, exhibiting a Tafel slope &gt;120 mV dec–1. Therefore, maximizing the current density range in which the desorption reaction is the rate‐determining step, can significantly reduce the overpotential. Herein, a surface sulfur decoration strategy is presented to modify the molybdenum carbide electrocatalyst and achieve coordinated adsorption/desorption kinetics, leading to a dominant Volmer–Heyrovsky mechanism across a wide range of current densities. Both experimental and theoretical results validate the surface charge redistribution induced by sulfur decoration, which subtly optimizes the Gibbs free energy of hydrogen adsorption and enhances the in‐plane polarization field. As a result, the as‐obtained surface sulfur‐decorated molybdenum carbide electrocatalyst exhibits coordinated adsorption/desorption kinetics and efficient hydrogen delivery, ultimately surpassing the commercial Pt/C electrocatalyst for high‐efficiency hydrogen evolution.

MIL-101(Fe) supported Au-Cu nanoalloy for enhanced electrochemical nitrogen fixation in gas–liquid-solid three-phase reactor

Low-temperature electrocatalytic nitrogen fixation technology is a green artificial nitrogen fixation technology. Here, we designed and synthesized AuxCuy/MIL-101 series catalysts, i.e., using simple alloy engineering strategy, the synthesized AuCu nanoalloy particles were efficiently loaded onto MIL-101(Fe) by one-step co-reduction. Experiments and calculations show that (Ⅰ) MIL-101(Fe) as support not only enhances the N2 enrichment ability of catalysts, but also facilitates the high dispersion of AuCu nanoparticles. (II) In AuCu nanoalloy, the strong coupling between Au-Cu sites bridges its effective electron transfer, improves the charge structure of Au sites, thereby enhancing the Au 5d-N2 π* interaction, which not only facilitates the adsorption of N2 by catalysts, but also weakens the N≡N triple bond and reduces RDS (N2 → NNH*, 0.38 eV). (III) Au-Cu alloying increases the hydrogen adsorption free energy (0.76 eV), which weakens the competitive adsorption between H+ and N2 by catalysts, and optimizes the charge transfer efficiency of AuxCuy/MIL-101 catalysts. Therefore, the overall NH3 yield and FE of AuxCuy/MIL-101 catalysts are higher than those of MIL-101, Cu/MIL-101 and Au/MIL-101. After optimization, Au1Cu1/MIL-101 with the highest ECSA and suitable Rct has the highest NRR activity (NH3 yield: 161.07 μg h−1 mg-1cat., FE: 58.86 %), which exceeds most Au-based catalysts. Meanwhile, the in-situ FTIR test results further indicate that Au-Cu alloying can accelerate the cleavage of N≡N and the adsorption of N2 by catalysts. This study demonstrates that the gold-copper alloying strategy not only promotes Au 5d feedback to N≡N bond, reduces RDS but also increases ΔGH*, inhibits proton adsorption, ultimately promoting Au1Cu1/MIL-101 catalyst to perform highly efficient NRR performance.

Anchoring ZnIn2S4 nanosheets on cross-like FeSe2 to construct photothermal-enhanced S-scheme heterojunction for photocatalytic H2 evolution

Rational design of the morphology and heterojunction to accelerate the separation of electron-hole pairs has played an indispensable role in improving the photocatalytic hydrogen evolution. ZnIn2S4 (ZIS) has aroused considerable attention in solar-to-chemical energy conversion due to its remarkable photoelectrical properties and relatively negative energy band, whereas it still suffers from the severe photogenerated carrier recombination and catalyst aggregation. Herein, guided by density functional theory calculations, the constructed FeSe2@ZnIn2S4 (FS@ZIS) heterojunction model has a hydrogen Gibbs free energy closer to zero compared with pure ZIS and FS, which is beneficial for hydrogen adsorption and desorption on the photocatalyst surface. Therefore, a novel cross-like core–shell FS@ZIS Step-scheme (S-scheme) heterojunction was synthesized successfully by in-situ growing ZIS nanosheets on the surface of cross-like FS. The structure with cross-like core–shell morphology not only inhibits the agglomeration of ZIS to increase specific surface area, but also provides a tight interface with S-scheme heterojunction. Moreover, the S-scheme heterojunction with a tight interface can effectively separate electron-hole pairs, leaving photoinduced charges with higher potentials. Furthermore, FS@ZIS-20 possesses exceptional photothermal capabilities, enabling the conversion of optical energy from visible and near infrared light to heat, thereby further enhancing the photocatalysis reaction. As a result, the cross-like core–shell FS@ZIS S-scheme heterojunction exhibits an excellent photocatalytic hydrogen evolution rate (7.640 mmol g−1 h−1), which is 24 times higher than that of pure ZIS (0.319 mmol g−1 h−1) under visible and near infrared light. Furthermore, employing more in-depth density functional theory calculations further investigates the charge transfer pathway of the FS@ZIS S-scheme heterojunction. This work provides insights into the construction of S-scheme heterojunctions with core–shell structure and photothermal effect for photocatalytic evolution hydrogen.

Improving the hydrogen storage performance of metal-decorated tetragonal boron carbide monolayer: First-principles investigations

Recently, two-dimensional systems have attracted considerable interest from scientists, due to their high H2 storage capacity and excellent reversibility. In this context, by means of DFT computations, we predict a novel system known as boron carbide, which can be formed by replacing 50% carbon atoms with boron atoms in tetragonal-graphene. We investigate the hydrogen adsorption performance of pristine and functionalized t-B4C4 sheets with the metals Li/Sc/Ti. Results indicate that metal-decorated t-B4C4 exhibits significantly lower H2 adsorption energies compared to pristine t-B4C4. Moreover, the hydrogen storage capacities for Li/Sc/Ti@t-B4C4 are 13.32%, 10.03% and 9.74% respectively. Furthermore, the desorption temperature exceeds the critical temperature of H2. Based on activation energy, H2 can migrate quickly on the t-B4C4 sheet during the adsorption/desorption cycles. Our results indicate that t-B4C4 functionalized with Li/Sc/Ti-metals can be an efficient material for hydrogen storage.

Electronic properties tailoring of th-XN (X = B, al) by surface functionalization

Hydrogenation and fluorination is a significant method to tune the electronic properties of two-dimensional (2D) materials. This paper theoretically predicted and analyzed the effects and regulatory mechanisms of surface functionalization on the electronic properties of 2D semiconductor tetrahex Boron/Aluminium Nitride (th-BN/th-AlN). The density-functional theory (DFT) calculations were employed to study various trends of band structure, effective mass, and work function. The results show that the electronic properties of 2D th-BN/th-AlN are susceptible to the surface adsorption atom species and coverage. Interconversions between semiconductor and metal properties or indirect and direct band structures in 2D th-XN (X = B, Al) can be realized by hydrogen and fluorine surface adsorption. The band gap expands and the work function decreases after H atom is adsorbed on the surface, while the band gap first increases and then decreases and the work function expands after F is adsorbed on the surface. After functionalization, the effective mass of the hole will be reduced to even lighter than that of an electron in certain directions. The change mechanisms of electronic properties in th-BN/AlN is surface adsorbed atoms will cause sp2-hybridized atoms to turn into sp3-hybridized atoms, which leads to the polarized double bonds between adjacent atoms becoming a single σ bond. The chemical bond changing will result in the band near the Fermi level gradually disappearing.

The Effects of Hot Isostatic Pressing (HIP) and Heat Treatment on the Microstructure and Mechanical Behavior of Electron Beam-Melted (EBM) Ti-6Al-4V Alloy and Its Susceptibility to Hydrogen.

The effects of the secondary processes of Hot Isostatic Pressing (HIP) at 920 °C and Heat Treatment (HT) at 1000 °C of Electron Beam-Melted (EBM) Ti-6Al-4V alloy on the microstructure and hydrogen embrittlement (HE) after electrochemical hydrogen charging (EC) were investigated. Comprehensive characterization, including microstructural analysis, X-ray diffraction (XRD), thermal desorption analysis, and mechanical testing, was conducted. After HIP, the β-phase morphology changed from discontinuous Widmanstätten to a more continuous structure, 10 times and ~1.5 times larger in length and width, respectively. Following HT, the β-phase morphology changed to a continuous "web-like" structure, ~4.5 times larger in width. Despite similar mechanical behavior in their non-hydrogenated state, the post-treated alloys exhibit increased susceptibility to HE due to enhanced hydrogen penetration into the bulk. It is shown that hydrogen content in the samples' bulk is inversely dependent on surface hydride content. It is therefore concluded that the formed hydride surface layer is crucial for inhibiting further hydrogen penetration and adsorption into the bulk and thus for reducing HE susceptibility. The lack of a hydride surface layer in the samples subject to HIP and HT highlights the importance of choosing secondary treatment process parameters that will not increase the continuous β-phase morphology of EBM Ti-6Al-4V alloys in applications that involve electrochemical hydrogen environments.

Double loading of nickel phosphide surface for efficient hydrogen evolution reaction

Metal phosphide, as a highly conductive, chemically stable catalyst material, modulating its hydrogen adsorption is crucial to enhance hydrogen evolution reaction (HER) activity. In this study, we propose a double loading strategy to build Ag and AgP2 heterogeneous structures on Ni2P nanosheets (Ag-AgP2/Ni2P). This is the first application of AgP2 materials in HER. This innovative synthesis was achieved by liquid-phase adsorption of precursors and heat-treatment phosphorization, surface adsorbed AgNO3 is converted to Ag-AgP2 double loading at the same time as Ni2P formation. Density functional theory (DFT) calculations reveal that the double loading structure optimizes charge distribution and d-band center. Its hydrogen adsorption free energy is closer to electroneutrality than that of single loading and simple heterostructures. Benefiting from the special structure, Ag-AgP2/Ni2P exhibits excellent HER performance in alkaline media, requiring only 78 mV overpotential to reach 10 mA cm−2 and stability up to 200 h. This dual loading strategy broadens the perspective of heterogeneous electrocatalyst development.