Electronegativity Of Metal Research Articles

Phosphorus Regulates Coordination Number and Electronegativity of Cobalt Atomic Sites Triggering Efficient Photocatalytic Water Splitting.

Optimizing the local electronic structure of a single-atom catalyst (SAC) is crucial for efficient photocatalytic hydrogen evolution reactions. This study synthesized a Co-P4/g-C3N4 heterostructure by selective phosphidation of the Co metal-organic framework/graphitic carbon nitride (Co-MOF/g-C3N4), converting the Co-O6 configuration into a highly electronegative, coordinatively unsaturated Co-P4 configuration anchored to a carbon matrix. P-doping induces strong charge redistribution, shifting the d-band center toward the Fermi level, transforming the Co sites from an electron-deficient state to an electron-rich state, and resulting in a significant reduction in the free energy barrier for HER to -0.08 eV. The Co-P4/g-C3N4 heterostructure demonstrated a HER rate of 13.51 mmol g-1 h-1, approximately 4.82-8.35 times greater than those of photocatalysts loaded with noble metals. The apparent quantum efficiency (AQE) was 28.45% at 380 nm. The synergistic effect of the low coordination number and high electronegativity metal sites significantly enhances the photocatalytic HER performance.

Screening Ir-Free Trimetallic Alloys with Consideration of Metal Electronegativity and Oxophilicity toward Ammonia Electrooxidation

Screening Ir-Free Trimetallic Alloys with Consideration of Metal Electronegativity and Oxophilicity toward Ammonia Electrooxidation

Systematic study of first-row transition metals chlorides as reaction accelerators for Mg/ MgH2 for hydrogen storage application

Mg has been proposed as a possible hydrogen storage material. However, Mg necessarily requires the addition of a suitable material with catalytic activity to improve hydriding and dehydriding reactions. Some chlorides of transition metals have been tested as improvers of hydriding/dehydriding reactions in Mg/MgH2. However, experimental preparation and tested conditions are dissimilar among different published reports. A systematic study of first-row transition metal chlorides as additives is presented here to understand the various factors affecting the hydriding/dehydriding reactions in Mg/MgH2 prepared and tested under the same conditions. The added transition metal chlorides (TMClx, x = oxidation state) include metals in oxidation states +4, +3, and +2 whenever commercially available. Additional chlorides, such as ZrCl4 and AlCl3, were included for comparison. The mixtures of Mg-TMClx were produced employing cryogenic ball milled and characterized by i) temperature-programmed hydriding and dehydriding, ii) X-ray photoelectron spectroscopy at Mg, transition metals, and chlorine 2p edges, iii) X-ray diffraction, and iv) scanning electron microscope. The best additives are VCl3>TiCl4>NiCl2>AlCl3. In contrast, the worst additives among the first-row transition metal chlorides were CrCl2, ZnCl2, and CuCl2. They do not improve at all the hydrogen uptake kinetics of pure Mg. Chemical state, side reactions, crystal structure, and morphology were discussed as factors affecting the behavior of the hydriding and dehydriding reactions. A complex interrelationship among these factors is observed. However, the electronegativity of the transition metal and an interaction of the type Mg-TM-Cl, are proposed as the main factors for the observed improvement of hydriding and dehydriding reactions.

The effect of Al and Zr content on corrosion of AlNiCoCuZr high-entropy alloys in a 5 wt% NaCl solution

High-entropy alloys are attractive structural materials for the design of apparatus for various chemical technologies due to their relative ease of production, corrosion resistance and high values of mechanical properties (hardness, strength). In the present work, the influence of aluminum and zirconium content on the corrosion resistance of Al(20−35)-Ni(5−15)-Co(15−30)-Cu(20−35)-Zr(5−40) high-entropy alloys was studied experimentally for the first time. Corrosion tests were performed in a 5 wt% NaCl aqueous solution during 1500 h at 298 K. It is established that the electronegative metals included in the alloy - Al and Zr are passivation components and with increasing their content in AlNiCoCuZr composition the corrosion rate in the studied conditions is decreased. It is shown that degradation of alloys occurs mainly as a result of nickel and cobalt hydroxide formation, the solubility of which is several orders of magnitude higher than that of aluminum hydroxide and zirconium hydroxide.

Electronegativity Impact on metal (Copper, Iron, Zinc) Lewis acid catalysts in the Biginelli Reaction: A Comparative Study

The Biginelli reaction is a very practical multi-component reaction, and the products 3,4-Dihydropyrimidine-2(1H)-ones (DHPMs) play an important role in the pharmacy scope. Herein, CuCl2, FeCl3, and ZnCl2 were used to investigate the catalytic activity differences among these metal Lewis acid catalysts for the Biginelli reaction under controlled conditions. Based on reaction mechanism, we believe that highly electronegative metals are beneficial for activating imines and enol intermediates, thereby increasing reaction yields.

Recent Advances in Halogen-Metal Exchange Reactions.

ConspectusThe halogen-metal exchange reaction is a very powerful method for preparing functionalized organometallic reagents in the fields of organic and organometallic chemistry. Since its inception, significant interest has been directed toward the on-demand development of new halogen-metal exchange reactions, primarily through the upgrading of exchange reagents. The enduring quest for optimal reactivity, superior functional group compatibility, and innovative synthetic applications of exchange reagents remains a fundamental objective. In the past several years, the emergence of some significant discoveries in halogen-metal exchange reactions has proclaimed a renaissance to this field. This Account outlines the latest advances within the domain contributed by the Knochel group, including the main points as follows.The stereoretentive I/Li exchange on stereodefined secondary alkyl iodides was developed for the synthesis of nonstabilized chiral secondary alkyllithium reagents. This provided a straightforward method to access chiral organolithium reagents, which can be trapped by various electrophiles or transmetalated with other metals such as copper, zinc, and magnesium, thus enabling the stereoselective synthesis of a series of functionalized compounds and natural products.Faster halogen-magnesium and halogen-zinc exchanges in toluene were realized using a novel kind of exchange reagent complexed with lithium alkoxide. These highly efficient exchange reactions are much faster than traditional ones and performed in an industrially friendly solvent. These advantages are of great value in practical synthesis, paving the way for new developments in this evolving area.Halogen-lanthanide exchanges and their novel applications in organic synthesis were established. These new exchanges introduced the lanthanide metals into halogen-metal exchange reactions for the first time, thereby opening new avenues in synthetic chemistry. Building on these achievements, a comparative analysis of the exchange reaction rates by kinetic study has quantified the relationship between the electronegativity of metals and the rates of halogen-metal exchanges.Br/Na exchange in continuous flow was achieved using a hexane-soluble exchange reagent, 2-ethylhexylsodium. This approach effectively circumvented the poor solubility of the organosodium reagent, which has proven to be of significant practical value and greatly enhanced the synthetic utility of the organosodium reagent in organic synthesis.These remarkable breakthroughs as mentioned above are fueled mainly by upgrading the exchange reagents, resulting in the development of new halogen-metal exchange reactions and innovative applications in organic synthesis. Given the importance of halogen-metal exchanges in synthetic chemistry, the pursuit of other types of exchange reactions, particularly those involving new metals, will be in continuous demand. This Account provides a timely summary of recent progress and will undoubtedly inspire further advances to drive this research field forward.

Tuning electronegativity environment of asymmetric oxygen vacancies in Sb-SnO2 promotes electrofiltration oxidation at low potential

Development of a 3D self-standing porous anode that can efficiently generate •OH at low potential remains exceptionally challenging for the electrofiltration technology. Herein, we propose a local microenvironment regulation strategy for precisely tuning electronegativity of asymmetric oxygen vacancy (Ov) via Ce atoms in microchannels of Sb-SnO2 anode to boost •OH generation. Both H2O and O2 adsorption on the Ce–Ov–Sn sites can be improved, and the asymmetric sites along with electrophilic O2 synergistically withdrew electrons from adsorbed H2O. Consequently, a 9.2 folds increase in the •OH yield is achieved for Ce-Sb-SnO2 compared with Sb-SnO2 at 1.62 V vs. SHE. Integrating Ce-Sb-SnO2 anode into electrofiltration system, the removal efficiency of 2,4-dichlorophenol reached 99.0 % (k = 0.233 min−1) with only 0.02 kWh·m−3 under high water flux of 1500 L·m−2·h−1. This work inspires us to design metal oxide electrodes from the view of tuning metal electronegativity differences and vacancies to achieve high performance.

Modulating Electron Density of Boron-Oxygen Groups in Borate via Metal Electronegativity for Propane Oxidative Dehydrogenation.

The robust electronegativity of the [BO3]3- structure enables the extraction of electrons from adjacent metals, offering a strategy for modulating oxygen activation in propane oxidative dehydrogenation. Metals (Ni 1.91, Al 1.5, and Ca 1.0) with varying electronegativities were employed to engineer borate catalysts. Metals in borate lacked intrinsic catalytic activity for propane conversion; instead, they modulated [BO3]3- group reactivity through adjustments in electron density. Moderate metal electronegativity favored propane oxidative dehydrogenation to propylene, whereas excessively low electronegativity led to propane overoxidation to carbon dioxide. Aluminum, with moderate electronegativity, demonstrated optimal performance. Catalyst AlBOx-1000 achieved a propane conversion of 47.5%, with the highest propylene yield of 30.89% at 550 °C, and a total olefin yield of 51.51% with a 58.92% propane conversion at 575 °C. Furthermore, the stable borate structure prevents boron element loss in harsh conditions and holds promise for industrial-scale catalysis.

Realizing the Tailored Catalytic Performances on Atomic Pt-Promoted Transition Metal Moieties Implanted Layered Double Hydroxides for Water Electrolysis.

High-performance production of green hydrogen gas is necessary to develop renewable energy generation technology and to safeguard the living environment. This study reports a controllable engineering approach to tailor the structure of nickel-layered double hydroxides via doped and absorbed platinum single atoms (PtSA) promoted by low electronegative transition metal (Mn, Fe) moieties (PtSA-Mn,Fe-Ni LDHs). We explore that the electron donation from neighboring transition metal moieties results in the well-adjusted d-band center with the low valence states of PtSA(doped) and PtSA(ads.), thus optimizing adsorption energy to effectively accelerate the H2 release. Meanwhile, a tailored local chemical environment on transition metal centers with unique charge redistribution and high valence states functions as the main center for H2O catalytic dissociation into oxygen. Therefore, the PtSA-Mn,Fe-Ni LDH material possesses a small overpotential of 42 and 288 mV to reach 10 mA·cm-2 for hydrogen and oxygen evolution, respectively, superior to most reported LDH-based catalysts. Additionally, the mass activity of PtSA-Mn,Fe-Ni LDHs proves to be 15.45 times higher than that of commercial Pt-C. The anion exchange membrane electrolyzer stack of PtSA-Mn,Fe-Ni LDHs(+,-) delivers a cell voltage of 1.79 V at 0.5 A·cm-2 and excellent durability over 600 h. This study presents a promising electrocatalyst for a practical water splitting process.

Density functional model of threshold voltage shifts at High-K/Metal gates

A density functional analysis of oxide dipole layers used to set the threshold voltages in high-K/metal CMOS gate stacks is given in terms of the band alignments and chemical trends of these component oxide layers. The oxides SrO, La2O3, HfO2 and Al2O3 are found to have similar band gaps and form a ‘staircase’ of band alignments, allowing them to shift the metal electrode Fermi level in both n-type and p-type directions. This analysis supersedes previous largely empirical models based on metal oxide ion densities or electronegativity scales.

Study on hydrogen desorption of ZrCoH3 promoted by doping Hf and Ti with DFT

This work aims to provide new insights into the hydrogen evolution of ZrCoH3. The transition metal elements Hf and Ti are designed to be added to ZrCoH3 by occupying Co atoms, Zr atoms, and interstitial sites. The effects of Hf and Ti atoms on the hydrogen evolution of ZrCoH3 are investigated through a first-principles study. The results show that the doping of Hf and Ti atoms can effectively improve the hydrogen desorption ability of ZrCoH3, which is related to the weak Co–H covalent interaction in the doping system, metallic properties, and the formation of Hf/Ti–H bonds. Hf atom doping has the best catalytic effect on the dehydrogenation of ZrCoH3, and the Hf atom can easily enter the ZrCoH3 body to form the Zr16Co16HfH48 compound. Although the Zr15Co16HfH48 compound has a low hydrogen dissociation energy and exhibits good hydrogen desorption performance, it requires a high energy cost when Hf occupies the Zr site in practical applications. When doped with the same element, the occupancy energy and hydrogen dissociation energy are inversely related. The hydrogen dissociation energy of ZrCoH3 is negatively correlated with the electronegativity of the dopant atom, namely, the lower the electronegativity of the dopant atom, the smaller the hydrogen dissociation energy of the system. This study confirms by simulation calculations that the use of low electronegativity metals to recombine with ZrCoH3 is an effective way to achieve ZrCoH3 destabilization.

Unravelling the influence of surface functional groups and surface charge on heavy metal adsorption onto carbonaceous materials: An in-depth DFT study

Theoretical analyses were explored for the adsorption of heavy metals in aqueous systems, focusing on the influence of surface charge and functional groups of carbonaceous materials. The approach involved the meticulous assignment and interpretation of active adsorption bands, achieved through modelling of Fourier Transform Infrared (FT-IR) and X-ray Photoelectron Spectroscopy (XPS) spectra. Additionally, atomic charges were analyzed, utilizing their chemical properties to glean valuable insights into the atomic-level intricacies of the adsorption process. The structural parameters of the carbonaceous surface reveal that in unsaturated models, heavy metals preferentially adsorb onto neighboring carbons due to facilitated electron transfer. Conversely, adsorption predominantly occurs in saturated models within functional groups, except for interactions involving the phenolic group, where it occurs on the carbonaceous matrix. Overall, negative ΔG values were observed across a range of temperatures from 285 to 315 K, as evidenced by Gibbs free energy values ranging from −72.93 kcal/mol (Ni2+ on carboxylate) to −4.98 kcal/mol (Cd2+ on ketone), confirming the spontaneous and thermodynamic feasibility nature of the adsorption processes for heavy metals on biochar across all evaluated functional groups, following the trend Ni2+ > Zn2+ > Co2+ > Cd2+. These trends can be rationalized in terms of: a) the size-dependence, where smaller cations such as Ni2+ (0.69 Å) form more stable adsorption complexes than Cd2+ (0.95 Å); b) charge transfer, higher adsorption energy (-55.60 kcal/mol) corresponds to a greater magnitude of charge transfer (0.32e); and c) the electronegativity of the respective metals, which are as follows: 1.367 for Ni2+, 1.349 for Co2+ and 1.336 for Zn2+. Consequently, Ni2+ exhibits a greater propensity to accept electrons from oxygen biochar than Co2+ and Zn2+ atoms. Finally, the assignment of IR and XPS is challenging in the laboratory, facing several endeavours. Our findings indicate a notable shift in the C―O stretching signal from 1631 cm−1 (in the clean system) to 1652 cm−1 upon Cd2+ adsorption, with Co2+, Ni2+, and Zn2+ showing shifts to 1690 cm−1 and 1685 cm−1 for the latter two cases, respectively. Therefore, the theoretical signals reported in the current work are a helpful tool as benchmark data to address and complement further experimental information. Indeed, the modelling of IR and XPS fit with some experimental values for some representative cases, implying appropriate modelling of the above systems.

In-situ utilization of As(III) enhances selective recovery of heavy metals from acid mine drainage by hydroxyl-enriched Fe-Mn binary oxide

As(III), a common pollutant in acid mine drainage (AMD), can provide potential active sites for the adsorption of heavy metals on adsorbents. In this study, Pb(II), As(III), and Cu(II) were sequentially recovered from AMD using hydroxyl-enriched Fe-Mn binary oxide (O-FMO) via the in-situ utilization strategy of As(III). The results showed that the prepared O-FMO demonstrated better adsorption performance under acidic conditions than FMO. O-FMO exhibited an outstanding selectivity (＞99.6%) for the removal of Pb(II) and As(III) via the generation of insoluble As-Pb complex in AMD and the immobilized Pb and As could be subsequently separated using respective acid and alkaline solutions. Furthermore, the recovered O-FMO containing residual As could promote the selective removal of Cu(II) (Selectivity ＞98.4 %) from the treated AMD. Mechanism analysis revealed that the oxidized As(V) on the O-FMO played a dominant role in promoting metals adsorption via electrostatic interaction and complexation. Pb(II) can directly form a generally stable complex with H3AsO4 (As(V)) under acidic conditions, thereby replacing the Cu(II) and Cd(II) which only form acid-soluble complexes with H2AsO4-1 (As(V)). Besides, metal electronegativity affects the traits and the formation sequence of As-metal complexes. Hence, the recovery of metal(loid)s (purity > 98.4 %) from AMD following the order: Pb(II), As(III), and Cu(II) could be achieved by reutilizing O-FMO. This work offers a unique approach for AMD remediation by utilizing pollutants to treat pollution.

Stabilizing Highly Active Ru Sites by Electron Reservoir in Acidic Oxygen Evolution.

Proton exchange membrane water electrolysis is hindered by the sluggish kinetics of the anodic oxygen evolution reaction. RuO2 is regarded as a promising alternative to IrO2 for the anode catalyst of proton exchange membrane water electrolyzers due to its superior activity and relatively lower cost compared to IrO2. However, the dissolution of Ru induced by its overoxidation under acidic oxygen evolution reaction (OER) conditions greatly hinders its durability. Herein, we developed a strategy for stabilizing RuO2 in acidic OER by the incorporation of high-valence metals with suitable ionic electronegativity. A molten salt method was employed to synthesize a series of high-valence metal-substituted RuO2 with large specific surface areas. The experimental results revealed that a high content of surface Ru4+ species promoted the OER intrinsic activity of high-valence doped RuO2. It was found that there was a linear relationship between the ratio of surface Ru4+/Ru3+ species and the ionic electronegativity of the dopant metals. By regulating the ratio of surface Ru4+/Ru3+ species, incorporating Re, with the highest ionic electronegativity, endowed Re0.1Ru0.9O2 with exceptional OER activity, exhibiting a low overpotential of 199 mV to reach 10 mA cm-2. More importantly, Re0.1Ru0.9O2 demonstrated outstanding stability at both 10 mA cm-2 (over 300 h) and 100 mA cm-2 (over 25 h). The characterization of post-stability Re0.1Ru0.9O2 revealed that Re promoted electron transfer to Ru, serving as an electron reservoir to mitigate excessive oxidation of Ru sites during the OER process and thus enhancing OER stability. We conclude that Re, with the highest ionic electronegativity, attracted a mass of electrons from Ru in the pre-catalyst and replenished electrons to Ru under the operating potential. This work spotlights an effective strategy for stabilizing cost-effective Ru-based catalysts for acidic OER.

Simultaneous adsorption of anionic and cationic species on UiO-66 and MIL-125 MOFs: Mechanisms & selectivity

Metal-organic frameworks (MOFs) have attractive properties, including regular pore structure, high specific surface area, tunable surface properties, and abundant active sites. Such properties have boosted their recent development in many fields, including water treatment. In this study, MOFs composed of tetravalent metals (Ti4+ and Zr4+) and dicarboxylate linker (terephthalate – BDC) were modified using surface functionalization and/or pore structure through defect engineering to enhance adsorption properties. It has been shown that the Ti-containing materials (MIL-125) show a greater affinity for cationic species, while the Zr-containing samples (UiO-66) have a higher affinity for anionic species. Surface charge and electrostatic interactions could account for such a difference in adsorption properties. Zeta potential measurements showed that MIL-125 has a more negative surface charge for both non-functionalized and amino-functionalized versions, which favors the interaction with cationic molecules. On the other hand, UiO-66 has a more positive surface, which facilitates interactions with anionic molecules. Within each MOF family, the non-functionalized structures emerged as the best-performing materials. Specifically, MIL-125(H) and UiO-66(H)_5eq, with 5eq denoting the amount of H2O added during synthesis, showed superior performance. Furthermore, by performing simultaneous adsorption experiments with anionic and cationic contaminants, it was found that the adsorption of the anionic dye acid orange 7 (AO7) onto the UiO-66 framework is primarily based on specific interactions between the sulfonic group (-SO3-) within the AO7 molecule and the inorganic core Zr6O4(OH)4 of UiO-66. The interaction between MIL-125 and the cationic dye methylene blue (MB) was found to be more delocalized, based on electrostatic and π-π interactions between the benzene domains. Finally, except for MIL-125(H), all the tested MOFs showed high stability in water and in the adsorption process. The higher stability of UiO-66 over MIL-125 materials can be attributed to steric effects and lower metal electronegativity. Compared to MIL-125(H), the higher stability of MIL-125(NH2) is probably related to the formation of intramolecular hydrogen bonds.

Enhancing Ion Mobility in Solids with Physics-Informed and AI-Driven Descriptors

The field of sustainable energy storage and conversion has witnessed increasing interest in ionic conductors due to their potential applications in electrochemical devices such as electrodes and solid electrolytes. In this study, we employed a combination of density functional theory investigations and artificial intelligence techniques to develop a robust descriptor for ion mobility [1,2]. Our descriptor incorporates factors like structural distortions, electronegativity, ionic radii, and oxidation states. By investigating various charge carrier chemistries and the anion and cation chemistries of the host lattice, we discovered that migration barriers are interconnected through linear scaling relations. Building upon this descriptor, we conducted a comprehensive study that employed both theoretical and experimental approaches to identify cathode materials with enhanced mobility for Mg-ions. Our focus was on oxide spinels, and we employed periodic density functional theory calculations to analyze the migration of Mg2+ ions and evaluate the electronic, geometrical, and stability properties of different transition metals within the spinel structures. Our findings reveal that electronegative transition metals, such as Rh, facilitate high mobility of Mg-ions and promote favorable cathode functionality within oxide spinel frameworks [3]. Based on these insights, we identified MgRh2O4 as a promising candidate and proceeded to prepare and characterize it structurally. This study opens up new possibilities for utilizing functional cathode materials with improved transport properties in battery-related applications. [1] M. Sotoudeh and A. Groß JACS Au 2022, 2, 463–471.[2] M. Sotoudeh, M. Dillenz, A. Groß, Adv. Energy Sustainability Res. 2021, 2, 2100113. [3] M. Sotoudeh, M. Dillenz, J. Döhn, J. Hansen, S. Dsoke, A. Groß, Chem. Mater. 2023, 35, 4786–4797.

Single-atom Au-modified CeO2 catalyst: Structure and its catalytic performance in 2,4-diaminotoluene methoxycarbonylation reaction

In the reaction of dimethyl carbonate (DMC) and 2,4-diaminotoluene (TDA), Au/CeO2 exhibits higher selectivity than CeO2 for dimethyl toluene-2,4-dicarbamate (TDC). However, its catalytic activity drops after H2 reduction (denoted as Au/CeO2-R). The characterization results illustrate that Au exists as a single atom with the primary species as Auδ+ in Au/CeO2, forming CexAu1−xO2 structure similar to solid solution. Whereas for Au/CeO2-R catalyst, Au mainly exists as Au0, forming the Au-O-Ce structure on CeO2 surface. Significantly, the strong interaction between Au and CeO2 increases Ce3+ and oxygen vacancies content, as well as modulates their acidic property. However, the catalytic activity of Au/CeO2-R is found to be lower than Au/CeO2 as the species formed by DMC dissociation on its surface are not easily desorbed. Other transition metals supported on CeO2 are also prepared, wherein Pt/CeO2 and Pd/CeO2 exhibit good TDC selectivity. In the end, the electronegativity and catalytic activity of metals are correlated.

Effect of Longer Waiting Time During OCP and Pre-Applied Cleaning Potential In Corrosion Analysis of Zinc Metal

Tafel analysis is a widely accepted technique for corrosion studies in electrochemistry. A general literature search for one of the electronegative metals, zinc, revealed serious deviations in corrosion results. In order to understand the reasons behind these deviations, zinc metal was investigated at macro and micro levels during and after the Tafel corrosion analysis. In-situ macro surface investigation during the OCP period and Tafel analysis were performed, and it was found that the zinc surface undergoes proceeding corrosion attack following the immersion in 3.5 wt.% NaCl solution. In-situ macro surface analysis exhibited that the pre-oxidation of the surface proceeds as nonuniform at local regions. SEM-EDS and XRD analysis proved that the particular crystal planes of the zinc form ZnO with increasing immersion time. A linear sweep voltammetry (LSV) technique was applied to detect the oxygen removal and starting hydrogen evolution potentials. Three identical Tafel experiments were performed on samples without any treatment, and another three consecutive Tafel experiments were performed on the samples which applied pre-reduction potential. Obtained results revealed that in-situ pre-applied reduction potential just before the Tafel analysis cleaned the surface and allowed uniform oxide formation, resulting in the lowest standard deviation of the calculated Tafel elements.

RuSe2-CoTe Heterogeneous Surfaces Coated with NC Layer for Excellent HER Performance under Alkaline Condition.

Electrocatalytic hydrogen production has been a promising high-purity hydrogen production technology, attracting a large number of researchers' research interest. Ru has a hydrogen binding capacity similar to Pt, but its price is far lower than Pt, making it a promising alternative to Pt. However, a single Se electronic structure modulation is not sufficient to enable RuSe2 to be used for practical applications on a large scale due to the lack of electrons. Therefore, choosing a suitable way to electronically modulate the Ru atoms in RuSe2 can effectively improve the activity of the catalyst. Cobalt telluride (CoTe) can significantly enhance electrocatalytic performance due to tellurium's low electronegativity and excellent metal properties. In this work, the NC layer possesses excellent electrical conductivity and CoTe acts as an electron donor to optimize the electronic structure locally and trigger electron transfer efficiently. The RuSe2-CoTe/NC electrode requires an overpotential of only 25.4 mV (10 mA cm-2), which is superior to that of RuSe2/NF (65 mV) and CoTe/NC (115 mV). Meanwhile, the Tafel slope of RuSe2-CoTe/NC (67.8 mV dec-1) was better than that of RuSe2/NF (113.6 mV dec-1) and CoTe/NC (209.5 mV dec-1), showing that the build-up of the superior heterojunction makes the RuSe2-CoTe/NC with better hydrogen evolution reaction (HER) reaction kinetics. In addition, after 30 h of long-term stability testing, no significant decrease in catalytic activity was observed, proving the good stability of the RuSe2-CoTe/NC catalyst.

Density functional analysis of oxide dipole layer voltage shifts in high κ/metal gate stacks

The mechanism of gate threshold voltage (VT) shifts observed in high κ/metal gate stacks is investigated by a density functional theory. This finds that VT depends on the band alignments and the chemical trends between the component oxide layers, such as HfO2, SrO, La2O3, Al2O3, and SiO2. Based on the electron counting rule, we have built three insulating SiO2/SrO, SiO2/La2O3, and SiO2/Al2O3 interfaces, all of which feature a clean bandgap. Two methods have been adopted to derive the band alignments between these four oxides, which are consistent with each other. The results show staggered, “staircase” band alignments and enable La2O3 and Al2O3 layers to shift the metal electrode Fermi level in opposite directions and to approach the Si conduction band and valence band edge positions, respectively. This analysis updates previous empirical models of this effect based on metal oxide ion densities or electronegativity scales and confirms that the oxide layer scheme is suitable for controlling the effective metal work functions in metal–oxide–semiconductor field-effect transistors.