Electron-electron Interaction Research Articles

Stability, Chemical Bonding, and Electron Lone Pair Localization in AsN at High Pressure by Density Functional Theory Calculations.

The covalent bonding framework of crystalline single-bonded cubic AsN, recently synthesized under high pressure and high temperature conditions in a laser-heated diamond anvil cell, is here studied by means of density functional theory calculations and compared to single crystal X-ray diffraction data. The precise localization of the nonbonding electron lone pairs and the determination of their distances and orientations are related to the presence of characteristic structural motifs and space regions of the unit cell dominated by repulsive electronic interactions, with the relative orientation of the electron lone pairs playing a key role in minimizing the energy of the structure. We find that the vibrational modes associated with the expression of the lone pairs are strongly localized, an observation that may have implications for the thermal conductivity of the compound. The results indicate the thermodynamic stability of the experimentally observed structure of AsN above ∼17 GPa, provide a detailed insight into the nature of the chemical bonding network underlying the formation of this compound, and open new perspectives to the design and high pressure synthesis of new pnictogen-based advanced materials for potential applications of energetic and technological relevance.

Electronic metal-support interactions for defect-induced Ru/Co-Sm2O3 mesosphere to achieve efficient NaBH4 hydrolysis activity

Crafting resilient catalysts that promote H2 production through the hydrolysis of hydrogen storage materials like sodium borohydride stands paramount for the impending hydrogen economy. In this study, we propose a versatile metal–organic framework (MOF)-assisted approach to systematically explore the impact of electron-metal support interaction (EMSI) of Ru-modified Co-Sm2O3 (Ru/Co-Sm2O3) on H2 evolution from NaBH4 hydrolysis. Strategic annealing at 800 °C induces cobalt vacancies on the Ru/Co-Sm2O3 surface, optimizing the exposure of active sites and amplifying mass-charge transfer efficiency. Consequently, the defect-enriched Ru/Co-Sm2O3 showcases an impressive hydrogen generation rate (HGR = 0.430 mol min−1 gcatalyst−1) and outstanding cycling resilience, eclipsing the performance of most contemporary catalysts. Experimental findings reveal that Sm can not only adjust the Ru lattice spacing to accommodate more BH4−, but also modulate the Co vacancy concentration, thus bolstering the charge transport and ameliorating the catalyst's electrical conductivity. DFT calculations confirm that the Michaelis-Menten/Eley-Rideal mechanism is more appropriate to explain the hydrolysis of NaBH4.

Robust and efficient hydrogen production performance using nitrogen- and phosphorus-doped microalgal carbon-based metal-free carbon composite

Carbon-based metal-free catalysts are attracting attention in different applications. However, these metal-free carbon materials do not have sufficient active sites, resulting in low catalytic activity. Therefore, modification of metal-free carbon materials with appropriate approaches is important. The simultaneous doping of different electronegative heteroatoms has a positive effect on catalytic performance due to the synergistic effect caused by the electronic interactions between different atoms compared to mono-doping. In this study, Spirulina platensis, a microalgae species that is easy to culture, was used as the carbon source. First, ammonia (NH3) and phosphoric acid (H3PO4) activation were used to modify the surface of activated carbon obtained from Spirulina platensis by KOH activation (SPAC). Thus, the SPAC surface is enriched with N(SPAC-N) and P atoms whose electronegativity is different from carbon. These modified carbon particles (SPAC-N-P) were used as a metal-free catalyst to increase the H2 production rate from NaBH4 methanolysis. XRD, TEM, TG/DTG, FTIR and XPS analyses were used for the characterization of the obtained catalysts. FTIR and XPS analyses showed successful incorporation of N, P and O atoms. HGR values of 5737, 6104 and 13,052 mL min−1gcat−1 by SPAC, SPAC-N and SPAC-N-P catalysts were obtained, respectively. There is a significant increase in the catalytic performance of the catalysts obtained with both NH3 and H3PO4 activations.

Revealing Hydrogen Spillover on 1T/2H MoS2 Heterostructures for an Enhanced Hydrogen Evolution Reaction by Scanning Electrochemical Microscopy.

The in situ characterization of the heterostructure active sites during the hydrogen evolution reaction (HER) process and the direct elucidation of the corresponding catalytic structure-activity relationships are essential for understanding the catalytic mechanism and designing catalysts with optimized activity. Hence, exploring the underlying reasons behind the exceptional catalytic performance necessitates a detailed analysis. Herein, we employed scanning electrochemical microscopy (SECM) to in situ image the topography and local electrocatalytic activity of 1T/2H MoS2 heterostructures on mixed-phase molybdenum disulfide (MoS2) with 20 nm spatial resolution. Our measurements provide direct data about HER activity, enabling us to differentiate the superior catalytic performance of 1T/2H MoS2 heterostructures compared to other active sites on the MoS2 surface. Combining this spatially resolved electrochemical information with density functional theory calculations and numerical simulations enables us to reveal the existence of hydrogen spillover from the 1T MoS2 surface to 1T/2H MoS2 heterostructures. Furthermore, it has been verified that hydrogen spillover can significantly enhance the electrocatalytic activity of the heterostructures, in addition to its strong electronic interaction. This study not only contributes to the future investigation of electrochemical processes at nanoscale active sites on structurally complex electrocatalysts but also provides new design strategies for improving the catalytic activity of 2D electrocatalysts.

Selective Orbital Coupling: An Adsorption Mechanism in Single-Atom Catalysis.

Quantitative understanding of the chemisorption on single-atom catalysts (SACs) by their electronic properties is crucial for the catalyst design. However, the physical mechanism is still under debate. Here, the CO catalytic oxidation on single transition metal (i.e., Sc, Ti, V, Cr, Mn, Fe, Co, Ni) dopants is used as a theoretical model to explore the correlations between the characteristics of electronic structures and the chemisorption on SACs. For these metal dopants, their atomic d orbitals form several nondegenerate and localized electronic states that are found to be selectively coupled with the π* orbital of the adsorbed O2, which we defined as selective orbital coupling. Based on the selective orbital coupling, we find that the alignment between the selected d state and the π* state determines the bond strength, regardless of the electron occupation number of the selected d states; the electron transfer to form M-O bonding can be provided by the support. Such electron transfer can be related with the electronic metal-support interaction. We attribute the origin of the chemisorption mechanism to the coexistence of the localized orbital of the single transition metal and the continuous energy band of the Au support. Finally, we illustrate how this mechanism dominates the variation trend of the reaction barriers. Our results unravel a fundamental adsorption mechanism in SAC systems.

Synthesis of Co0·52Cu0·48/Cu@S–C arrays for the enhanced performance of hydrazine-assisted hydrogen production

The development of efficient bifunctional catalysts is the key technology to replace oxygen evolution reaction (OER) with hydrazine oxidation reaction (HzOR) with lower theoretical potential to achieve high efficiency and energy-saving hydrogen production. In this work, the Co0·52Cu0·48/Cu@S–C (−1.3 V) composite with flower-like array was prepared by two-step electrodeposition coupled pyrolysis method. The electrochemical measurements showed that the driving voltages of the optimal composite for HzOR and hydrogen evolution reaction (HER) are respectively −118 mV and 47 mV at a current density (j) of 10 mA cm−2. The excellent performance of Co0·52Cu0·48/Cu@S–C (−1.3 V) composite is attributed to the fact that the flower-like structure exposes more active areas and facilitates the diffusion of electrolyte, the strong electron interaction between Co0·52Cu0·48/Cu and S–C substrate, which can be verified by X-ray photoelectron spectroscopy (XPS), enhances the electrical conductivity, the Co0·52Cu0·48/Cu heterogeneous interface reduces the water dissociation barrier and facilitates the dehydrogenation kinetics of N2H4 determined by density functional theory (DFT) calculations. Due to the excellent performance of Co0·52Cu0·48/Cu@S–C (−1.3 V), the overall hydrazine splitting (OHzS) electrolytic cell was constructed with Co0·52Cu0·48/Cu@S–C (−1.3 V) as electrodes. The results showed the voltages required by the cell are 36, 210 and 282 mV at the current density values of 10, 100 and 200 mA cm−2 respectively, showing that Co0·52Cu0·48/Cu@S–C (−1.3 V) can be used for energy-saving hydrogen production by hydrazine assisted water electrolysis.

ORR properties of PtM (M = Fe and Ni) ordered alloys with the effect of small molecules of cyanamide

Ordered Pt alloy electrocatalysts have a special geometric structure and exhibit excellent oxygen reduction reaction (ORR) catalytic performance. Herein, we successfully prepared PtFe/PtNi ordered alloy catalysts by thermal annealing method under the protection of the encapsulated shell formed by pyrolysis of cyanamide molecules as well as the effect of the N element entering into the alloy system to cause defects, and kept the average particle size below 4 nm. The ordered structure enhances the electronic interactions, keeps more Pt0 valence states present and improves the ORR catalytic activity. Under acidic conditions, the PtFe ordered alloy catalyst had a mass activity of 0.752 A mgPt−1 and a specific activity of 1.138 mA cmPt−2, both of which were superior to the commercial Pt/C and disordered PtFe alloy. Importantly, the strong interaction between ordered Pt and Fe prevents the leaching of Fe and maintains high mass activity after a long period of circulation. DFT calculations show that the ordered PtFe alloy has a low reaction energy barrier, which is favorable for ORR.

Interfacial Electronic Interactions Between Ultrathin NiFe-MOF Nanosheets and Ir Nanoparticles Heterojunctions Leading to Efficient Overall Water Splitting.

Creating specific noble metal/metal-organic framework (MOF) heterojunction nanostructures represents an effective strategy to promote water electrolysis but remains rather challenging. Herein, a heterojunction electrocatalyst is developed by growing Ir nanoparticles on ultrathin NiFe-MOF nanosheets supported by nickel foam (NF) via a readily accessible solvothermal approach and subsequent redox strategy. Because of the electronic interactions between Ir nanoparticles and NiFe-MOF nanosheets, the optimized Ir@NiFe-MOF/NF catalyst exhibits exceptional bifunctional performance for the hydrogen evolution reaction (HER) (η10 = 15mV, η denotes the overpotential) and oxygen evolution reaction (OER) (η10 = 213mV) in 1.0m KOH solution, superior to commercial and recently reported electrocatalysts. Density functional theory calculations are used to further investigate the electronic interactions between Ir nanoparticles and NiFe-MOF nanosheets, shedding light on the mechanisms behind the enhanced HER and OER performance. This work details a promising approach for the design and development of efficient electrocatalysts for overall water splitting.

Local gate control of Mott metal-insulator transition in a 2D metal-organic framework

Electron-electron interactions in materials lead to exotic many-body quantum phenomena, including Mott metal-insulator transitions (MITs), magnetism, quantum spin liquids, and superconductivity. These phases depend on electronic band occupation and can be controlled via the chemical potential. Flat bands in two-dimensional (2D) and layered materials with a kagome lattice enhance electronic correlations. Although theoretically predicted, correlated-electron Mott insulating phases in monolayer 2D metal-organic frameworks (MOFs) with a kagome structure have not yet been realised experimentally. Here, we synthesise a 2D kagome MOF on a 2D insulator. Scanning tunnelling microscopy (STM) and spectroscopy reveal a MOF electronic energy gap of ∼200 meV, consistent with dynamical mean-field theory predictions of a Mott insulator. Combining template-induced (via work function variations of the substrate) and STM probe-induced gating, we locally tune the electron population of the MOF kagome bands and induce Mott MITs. These findings enable technologies based on electrostatic control of many-body quantum phases in 2D MOFs.

Observation of current whirlpools in graphene at room temperature.

Electron-electron interactions in high-mobility conductors can give rise to transport signatures resembling those described by classical hydrodynamics. Using a nanoscale scanning magnetometer, we imaged a distinctive hydrodynamic transport pattern-stationary current vortices-in a monolayer graphene device at room temperature. By measuring devices with increasing characteristic size, we observed the disappearance of the current vortex and thus verified a prediction of the hydrodynamic model. We further observed that vortex flow is present for both hole- and electron-dominated transport regimes but disappears in the ambipolar regime. We attribute this effect to a reduction of the vorticity diffusion length near charge neutrality. Our work showcases the power of local imaging techniques for unveiling exotic mesoscopic transport phenomena.

Fragility crossover mediated by covalent-like electronic interactions in metallic liquids

Abstract Fragility is one of the central concepts in glass and liquid sciences, as it characterizes the extent of deviation of viscosity from Arrhenius behavior and is linked to a range of glass properties. However, the intervention of crystallization often prevents the assessment of fragility in poor glass-formers, such as supercooled metallic liquids. Hence experimental data on their compositional dependence are scarce, let alone fundamentally understood. In this work, we use fast scanning calorimetry to overcome this obstacle and systematically study the fragility in a ternary La-Ni-Al system, over previously inaccessible composition space. We observe fragility dropped in a small range with the Al alloying, indicating an alloying-induced fragility crossover. We use x-ray photoelectron spectroscopy, resistance measurements, electronic structure calculations, and DFT-based deep-learning atomic simulations to investigate the cause of this fragility drop. These results show that the fragility crossover can be fundamentally ascribed to the electronic covalency associated with the unique Al-Al interactions. Our findings provide insight into the origin of fragility in metallic liquids from an electronic structure perspective and pave a new way for the design of metallic glasses.

Coupling Interaction between Precisely Located Pt Single‐Atoms/Clusters and NiCo‐Layered Double Oxide to Boost Hydrogen Evolution Reaction

AbstractCatalysts based on Pt single atom (SA) on metal oxides have shown tremendous potentials for alkaline hydrogen evolution reaction (HER), but they are severely limited by insufficient electron interactions of Pt sites and supports. Herein, a new methodology is developed to precisely locate Pt SAs and Pt clusters into NiCo layered double oxide (LDO) nanosheets, achieved using a dual‐ion etching process with subsequent phase transformation method. Uniquely, the Pt SAs are inserted into LDO layers to form Pt─Co bonds by occupying partial Ni positions, significantly strengthening electron interactions with NiCo LDO and promoting activity of HER. Results from density functional theory calculations indicate that the H* species are preferentially absorbed onto O sites on top of these Pt SAs, which are coupled with their adjacent Pt clusters to accelerate water dissociation in the Volmer step. As‐obtained Pt─NiCo LDO exhibits a low overpotential of 92 mV at 10 mA cm−2 and a Tafel slope of 73 mV dec−1, an excellent stability over 105 hours at 60 mA cm−2, and its mass activity is 6 times higher than commercial 20% Pt/C. This study highlights essential functions of coupling interactions between Pt SAs/clusters and LDOs to boost HER for hydrogen energy production.

Structural and electronic transport properties of Zn- and Ga-doped Bi2-xSbxTe3-ySey topological insulator single crystals.

A comprehensive study of structural and magnetotransport properties of pristine Bi2-xSbxTe3-ySey (BSTS) single crystals and doped with Zn (BSTS:Zn) and Ga (BSTS:Ga) are presented here. Magnetic field dependent Hall resistivities of the single crystals indicate that the holes are the majority carriers. The field dependent resistivity curves at different temperatures of the crystals display cusp-like characteristics at low magnetic fields, attributed to two-dimensional (2D) weak antilocalization (WAL) effect. The Hikami-Larkin-Nagaoka (HLN) equation fit to the low field WAL effects at various temperatures reveal a phase coherence length (lϕ) that decreases as temperature increases. The variation of lϕ with temperature follows T-0.41 power law for BSTS:Zn, suggesting that the dominant dephasing mechanism is a 2D electron-electron (e-e) interactions. For pristine BSTS and BSTS:Ga, lϕ(T) is described by considering a coexistence of 2D e-e and electron-phonon (e-p) interactions in the single crystals. The temperature variation of the longitudinal resistance in BSTS:Ga is described by three-dimensional (3D) Mott variable range hoping model. In contrast, the transport mechanisms of both pristine BSTS and BSTS:Zn are described by a combination of 2D WAL/EEI models and 3D WAL.&#xD.

Magnetically propagating Hund’s exciton in van der Waals antiferromagnet NiPS3

Magnetic van der Waals (vdW) materials have opened new frontiers for realizing novel many-body phenomena. Recently NiPS3 has received intense interest since it hosts an excitonic quasiparticle whose properties appear to be intimately linked to the magnetic state of the lattice. Despite extensive studies, the electronic character, mobility, and magnetic interactions of the exciton remain unresolved. Here we address these issues by measuring NiPS3 with ultra-high energy resolution resonant inelastic x-ray scattering (RIXS). We find that Hund’s exchange interactions are primarily responsible for the energy of formation of the exciton. Measuring the dispersion of the Hund’s exciton reveals that it propagates in a way that is analogous to a double-magnon. We trace this unique behavior to fundamental similarities between the NiPS3 exciton hopping and spin exchange processes, underlining the unique magnetic characteristics of this novel quasiparticle.

Electronic Metal-Support Interactions Boost *OOH Intermediate Generation in Cu/In2Se3 for Electrochemical H2O2 Production.

Two-electron oxygen reduction reaction (2e- ORR) is a promising method for the synthesis of hydrogen peroxide (H2O2). However, high energy barriers for the generation of key *OOH intermediates hinder the process of 2e- ORR. Herein, we prepared a copper-supported indium selenide catalyst (Cu/In2Se3) to enhance the selectivity and yield of 2e- ORR by employing an electronic metal-support interactions (EMSIs) strategy. EMSIs-induced charge rearrangement between metallic Cu and In2Se3 is conducive to *OOH intermediate generation, promoting H2O2 production. Theoretical investigations reveal that the inclusion of Cu significantly lowers the energy barrier of the 2e- ORR intermediate and impedes the 4e- ORR pathway, thus favoring the formation of H2O2. The concentration of H2O2 produced by Cu/In2Se3 is ~2 times than In2Se3, and Cu/In2Se3 shows promising applications in antibiotic degradation. This research presents a valuable approach for the future utilization of EMSIs in 2e- ORR.

Strong Interactions between Au Nanoparticles and BiVO4 Photoanode Boosts Hole Extraction for Photoelectrochemical Water Splitting

AbstractStrong metal‐support interaction (SMSI) is widely proposed as a key factor in tuning catalytic performances. Herein, the classical SMSI between Au nanoparticles (NPs) and BiVO4 (BVO) supports (Au/BVO‐SMSI) is discovered and used innovatively for photoelectrochemical (PEC) water splitting. Owing to the SMSI, the electrons transfer from V4+ to Au NPs, leading to the formation of electron‐rich Au species (Auδ−) and strong electronic interaction (i.e., Auδ−‐Ov‐V4+), which readily contributes to extract photogenerated holes and promote charge separation. Benefitted from the SMSI effect, the as‐prepared Au/BVO‐SMSI photoanode exhibits a superior photocurrent density of 6.25 mA cm−2 at 1.23 V versus the reversible hydrogen electrode after the deposition of FeOOH/NiOOH cocatalysts. This work provides a pioneering view for extending SMSI effect to bimetal oxide supports for PEC water splitting, and guides the interfacial electronic and geometric structure modulation of photoanodes consisting of metal NPs and reducible oxides for improved solar energy conversion efficiency.

Unified Treatment of Light Emission by Inelastic Tunneling: Interaction of Electrons and Photons beyond the Gap

Unified Treatment of Light Emission by Inelastic Tunneling: Interaction of Electrons and Photons beyond the Gap

Mobile infrastructure quality, regulatory quality, government effectiveness: Does e‐government development matter?

AbstractThere is a great deal of interest in how mobile infrastructure quality, regulatory quality, and a nation's capacity to develop efficient e‐government systems affect government effectiveness. The literature ignores the part electronic government plays in either the regulatory quality‐government effectiveness or mobile infrastructure quality‐government effectiveness nexuses, despite the fact that existing research indicates that the effects of these factors on government effectiveness vary across nations. Secondary data for 52 African nations was extracted from World Governance Indicator (WGI), Mobile Connectivity Index (MCI), and United Nations E‐government Database to empirically investigate the mediating relationship of e‐governments using hypothesized model. The positivist paradigm is considered appropriate for this study because it focuses on validating and testing a hypothesized model. The results show a significant relationship between mobile infrastructure quality and e‐government development, regulatory quality and e‐government development, e‐government and government effectiveness. However, there was no significant relationship between mobile infrastructure quality and government effectiveness. Additionally, e‐government was found to mediate the relationship between regulatory quality and government effectiveness and the relationship between mobile infrastructure quality and government effectiveness. This suggests that government effectiveness is enhanced when a country is able to develop and implement a good electronic system. The successful implementation of e‐governance practices offers better delivery of services to citizens, improved interactions with business, citizen empowerment through access to information, greater convenience, and cost reductions. In addition, establishing protections and legal reforms will be needed to ensure, among other things, the privacy, security and legal recognition of electronic interactions and electronic signatures.

Significantly improved dehydrogenation of dodecyl-N-ethylcarbazole over supported PdFe bimetallic nanocatalysts via polydopamine surface modification of Al2O3

N-ethylcarbazole (NEC) has great application prospects in hydrogen storage due to its ability to dehydrogenate at lower energy and high hydrogen storage performance. Developing supported metal catalysts with high catalytic activity and stability is key to achieving large-scale application of LOHC hydrogen storage technology. In this paper, bimetallic FePd/Al2O3@PDA-GR catalysts used for the dehydrogenation process of 12H-NEC were prepared by stepwise reduction methods, including chemical reduction and galvanic replacement, using PDA-coated Al2O3 as the support. The characterization results showed that adding PDA could anchor the metal particles, improve the dispersion of metal particles on the support surface, and reduce the agglomeration phenomenon. The nanoparticles of bimetallic catalysts prepared by the galvanic replacement were small, with the particle size distribution of 0.86 nm-2.78 nm, and an average size of 1.52 nm. The large number of exposed active sites enabled the catalysts to reduce the dosage of Pd while still possessing excellent catalytic performance. And part of Pd was coated on Fe NPs in the Fe5Pd1/Al2O3@PDA-GR catalysts prepared by galvanic replacement, which improved the atom utilization of Pd. And there is an obvious electronic interaction between Fe and Pd. In the dehydrogenation process of 12H-NEC to NEC, The prepared FePd/Al2O3@PDA-GR catalyst exhibited excellent catalytic performance and had a significantly greater dehydrogenation efficiency than found in the literature, 95% for 1 h and 100% for 3 h at 180 °C. The temperature drop to 160 °C did not affect the dehydrogenation efficiency, which remained at 98.1% for 3 h. The prepared catalyst had good stability, and the dehydrogenation efficiency was 93.1% after five successive cycles.

Local charge rectification and electronic interactions in ZnIn2S4-x-Bi2MoO6-x heterojunction for enhancing synergistic piezo-photocatalytic hydrogen evolution and benzylamine oxidation

The synergistic utilization of vacancies and heterojunctions in piezo-photocatalysis holds great promise for mitigating the issue of charge recombination. However, the charge aggregation effect in vacancies and the disordered positive and negative charge centers in piezoelectric materials may potentially compromise the performance of synergistic piezo-photocatalysis. Here, the well-designed dual vacancies of ZnIn2S4-x and Bi2MoO6-x S-scheme heterojunction (BZ) was prepared for synergistic piezo-photocatalytic amines coupling to generate imines integrated with H2 production. Impressively, BZ-2 demonstrated an efficient N-benzylidenebenzylamine production rate of 4680 µmol g−1 h−1 and H2 formation rate of 4480 µmol g−1 h−1 without using any solvent or cocatalyst, where the formation rate of H2 is 10.25 times greater than that of ZnIn2S4-x. Experimental data and DFT calculations demonstrated that the presence of dual vacancies induces the formation of an interfacial Bi-S bond, which effectively regulates electronic interactions and rectifies charge disorder at the surface of the S-scheme heterojunction. Furthermore, this interfacial Bi-S bond acts as a strain center for providing a substantial electric field to drive charge transfer. Additionally, the electronic structural coupling contributes to lowering the activation energy and enhancing the reaction kinetics. This study offers profound insights into the relationship between atomic defects and S-scheme heterojunctions in piezo-photocatalysis, facilitating the design of high-efficiency materials.