Electron-electron Interaction Research Articles

Supported IrO2 Nanocatalyst with Multilayered Structure for Proton Exchange Membrane Water Electrolysis.

The design of a low-iridium-loading anode catalyst layer with high activity and durability is a key challenge for a proton exchange membrane water electrolyzer (PEMWE). Here, the synthesis of a novel supported IrO2 nanocatalyst with a tri-layered structure, dubbed IrO2@TaOx@TaB that is composed of ultrasmall IrO2 nanoparticles anchored on amorphous TaOx overlayer of TaB nanorods is reported. The composite electrocatalyst shows great activity and stability toward the oxygen evolution reaction (OER) in acid, thanks to its dual-interface structural feature. The electronic interaction in IrO2/TaOx interface can regulate the coverage of surface hydroxyl groups, the Ir3+/ Ir4+ ratio, and the redox peak potential of IrO2 for enhancing OER activity, while the dense TaOx overlayer can prevent further oxidation of TaB substrate and stabilize the IrO2 catalytic layers for improving structural stability during OER. The IrO2@TaOx@TaB can be used to fabricate an anode catalyst layer of PEMWE with an iridium-loading as low as 0.26mgcm-2. The low-iridium-loading PEMWE delivers high current densities at low cell voltages (e.g., 3.9Acm-2@2.0 V), and gives excellent activity retention for more than 1500h at 2.0Acm-2 current density.

S‐scheme MnO2/Co3O4 sugar‐gourd nanohybrids with abundant oxygen vacancies for efficient visible‐light‐driven CO2 reduction

Converting CO2 to carbon‐based fuels using solar energy via photocatalysis is a promising approach to boost carbon neutrality. However, the solar‐to‐chemical conversion efficiency is hampered by interconnected multiple factors including insufficient light absorption, low separation efficiency of photogenerated carriers as well as complex and sluggish surface reaction kinetics. Herein, we incorporate MnO2 nanowires and Co3O4 hollow polyhedrons with abundant oxygen vacancies (Vo) into MnO2/Co3O4 sugar‐gourd nanohybrids for boosting CO2 photoreduction. The MnO2/Co3O4 nanohybrids not only display strong absorption in the visible–near infrared region, but also facilitate the separation of photogenerated carriers in terms of S‐scheme transfer pathway, supplying abundant electrons for CO2 reduction reaction. Furthermore, the presence of VO enhances the separation efficiency of photogenerated carriers and promotes the chemical adsorption to CO2 molecules. In addition, the interfacial electronic interaction between MnO2 and Co3O4 also contributes to the chemical adsorption and activation to CO2. Owing to the synergy of S‐scheme transfer pathway and VO, the MnO2/Co3O4 hybrids exhibit greatly enhanced photocatalytic activity towards CO2 reduction under the irradiation of visible light in comparison with bare MnO2 and Co3O4, delivering a CO evolution rate of 15.9 umol g−1 h−1 with a 100% selectivity.

Enhanced Electrical Conductivity of Polyoxometalates by Bridging with Mixed‐Valent Multinuclear Platinum Complexes

AbstractPolyoxometalates (POMs) are nanosized molecular metal oxide anion clusters with tuneable structures and functionalities, and they exhibit a redox chemistry and catalytic activity in multielectron redox processes. These are typically poor electrical conductors (<10−10 Scm−1), which is attributed to negligible electronic interactions among anions in the solid state. Since the reduced electrons on the d0 metals in POMs are delocalized, electrical conductivity was improved when judicious pathways for the electrons were created by bridging the POMs. Utilized with the electronic interactions between bridging oxygen atoms with the highest occupied molecular orbital in the POMs and the metal dz2 orbitals in the multinuclear platinum complexes, and three mixed‐valent assemblies were synthesized and characterized. Simply mixing Keggin‐type or Dawson‐type POMs with tetranuclear or trinuclear platinum complexes in solution afforded three single crystals, and all three compounds were paramagnetic with mixed oxidation states and better conductivities at room temperature than the parent compounds.

Identification of a Weak Interaction between the Spin-Only 4f-Electronic System of Trivalent Gd Ion and a Photoexcited Cyclic π Electronic System.

An electronic interaction between the spin-only 4f-electronic system and the photoexcited π cyclic system has been identified in the anionic bis(phthalocyaninato)gadolinium(III) complex [Pc2Gd]- by using variable-temperature variable-magnetic-field magnetic circular dichroism (VTVH MCD). Two positive MCD A-term patterns, corresponding to the QH and QL absorption bands, were observed to increase in intensity as the temperature decreased, indicating a ferromagnetic-type interaction between spin angular momentum S of the 4f system and orbital angular momentum L of the photoexcited π system. A theoretical model incorporating the S-L interaction constant CSL was fitted to the VTVH MCD spectra, confirming the presence of a weak interaction, whose intensity was determined as CSL = 0.27 cm-1 for QL and CSL = 0.02 cm-1 for QH. Ab initio calculations using the RASSCF and RASSI methods revealed that the inclusion of the excited state calculations with the spin multiplicity (2S + 1) of 6 was crucial for assigning ΔSL and CSL values. This underscores the essential role of the 6PJ term in accurately modeling the S-L interaction in [Pc2Gd]-.

Enhanced Electrical Conductivity of Polyoxometalates by Bridging with Mixed-Valent Multinuclear Platinum Complexes.

Polyoxometalates (POMs) are nanosized molecular metal oxide anion clusters with tuneable structures and functionalities, and they exhibit a redox chemistry and catalytic activity in multielectron redox processes. These are typically poor electrical conductors (<10-10 Scm-1), which is attributed to negligible electronic interactions among anions in the solid state. Since the reduced electrons on the d0 metals in POMs are delocalized, electrical conductivity was improved when judicious pathways for the electrons were created by bridging the POMs. Utilized with the electronic interactions between bridging oxygen atoms with the highest occupied molecular orbital in the POMs and the metal dz2 orbitals in the multinuclear platinum complexes, and three mixed-valent assemblies were synthesized and characterized. Simply mixing Keggin-type or Dawson-type POMs with tetranuclear or trinuclear platinum complexes in solution afforded three single crystals, and all three compounds were paramagnetic with mixed oxidation states and better conductivities at room temperature than the parent compounds.

Advances in Spin‐Modulated Electrocatalysis of Oxygen Evolution Reaction

AbstractElectrochemical splitting of water for hydrogen generation has emerged as a potential strategy for transitioning towards renewable energy sources and mitigating the environmental impact of fossil fuel dependence. However, the efficiency of water splitting is mainly hindered by oxygen evolution reaction (OER) at the anode side, which involves kinetically sluggish four proton‐coupled electron‐transfer steps. Recent studies on OER demonstrate that a spin‐dependent mechanism governs the reaction kinetics, wherein the electronic exchange interactions in the catalytic activity of transition metals can provide a spin‐selective channel to filter out electron spins with the right orientation during the formation of O2. Maximizing efficiency and stability of such catalysts require optimization the geometric and electrical structures of transition metal systems. In addition, it is vital to understand the OER mechanism with spin considerations to be familiar with the connection between spin, charge, orbital, and lattice characteristics. This review focuses on current developments in understanding and the use of the spin‐related effect in the OER mechanism.

Interfacial Electronic Interactions Promoted Activation for Nitrate Electroreduction to Ammonia over Ag‐modified Co3O4

Electrocatalytic nitrate (NO3−) reduction to ammonia (NRA) offers a promising pathway for ammonia synthesis. The interfacial electronic interactions (IEIs) can regulate the physicochemical capabilities of catalysts in electrochemical applications, while the impact of IEIs on electrocatalytic NRA remains largely unexplored in current literature. In this study, the high‐efficiency electrode Ag‐modified Co3O4 (Ag1.5Co/CC) is prepared for NRA in neutral media, exhibiting an impressive nitrate conversion rate of 96.86%, ammonia Faradaic efficiency of 96.11%, and ammonia selectivity of ~100%. Notably, the intrinsic activity of Ag1.5Co/CC is ~81 times that of Ag nanoparticles (Ag/CC). Multiple characterizations and theoretical computations confirm the presence of IEIs between Ag and Co3O4, which stabilize the CoO6 octahedrons within Co3O4 and significantly promote the adsorption of reactants (NO3−) as well as intermediates (NO2− and NO), while suppressing the Heyrovsky step, thereby improving nitrate electroreduction efficiency. Furthermore, our findings reveal a synergistic effect between different active sites that enables tandem catalysis for NRA: NO3− reduction to NO2− predominantly occurs at Ag sites while NO2− tends to hydrogenate to ammonia at Co sites. This study offers valuable insights for the development of high‐performance NRA electrocatalysts.

Interfacial Electronic Interactions Promoted Activation for Nitrate Electroreduction to Ammonia over Ag-modified Co3O4.

Electrocatalytic nitrate (NO3-) reduction to ammonia (NRA) offers a promising pathway for ammonia synthesis. The interfacial electronic interactions (IEIs) can regulate the physicochemical capabilities of catalysts in electrochemical applications, while the impact of IEIs on electrocatalytic NRA remains largely unexplored in current literature. In this study, the high-efficiency electrode Ag-modified Co3O4 (Ag1.5Co/CC) is prepared for NRA in neutral media, exhibiting an impressive nitrate conversion rate of 96.86%, ammonia Faradaic efficiency of 96.11%, and ammonia selectivity of ~100%. Notably, the intrinsic activity of Ag1.5Co/CC is ~81 times that of Ag nanoparticles (Ag/CC). Multiple characterizations and theoretical computations confirm the presence of IEIs between Ag and Co3O4, which stabilize the CoO6 octahedrons within Co3O4 and significantly promote the adsorption of reactants (NO3-) as well as intermediates (NO2- and NO), while suppressing the Heyrovsky step, thereby improving nitrate electroreduction efficiency. Furthermore, our findings reveal a synergistic effect between different active sites that enables tandem catalysis for NRA: NO3- reduction to NO2- predominantly occurs at Ag sites while NO2- tends to hydrogenate to ammonia at Co sites. This study offers valuable insights for the development of high-performance NRA electrocatalysts.

Regulating Adsorption Behavior of Reactants on NiO/CuO/Co3O4 Surface by Electronic Effect to Promote Electrosynthesis

AbstractDeveloping efficient electrooxidation 5‐hydroxymethylfurfural (HMF) catalysts with high selectivity and fast reaction kinetic is challenging. The HMF oxidation reaction (HMFOR) involves the adsorption of HMF and OH− on the catalyst, thus understanding the adsorption behavior between the catalyst surface and reactants is vital. In this work, by studying the relationship between HMFOR performance and the adsorption behavior of reactants on different transition metal oxides (TMOs), it is discovered that the catalytic performance of TMOs is related to the adsorption capacity of OH− and HMF simultaneously. Subsequently, TMOs with different HMF and OH− adsorption abilities are coupled to further optimize the catalytic performance of HMFOR. Experimental and theoretical calculation results indicate that the electronic interactions between different TMOs can regulate the substrate adsorption behavior and electron transfer ability of the catalysts, which is beneficial for HMFOR. Among them, due to the strong interaction between the three components optimizes the adsorption capacity for HMF and OH−, NiO/CuO/Co3O4 exhibits the best HMFOR performance with FDCA selectivity of 99.6 % and formation rate of 16.45 mmol gcat−1 h−1. This work provides a design principle for HMFOR catalysts by modulating the adsorption behavior of reaction molecules.

Integrative catalytic pairs for efficient multi-intermediate catalysis.

Single-atom catalysts (SACs) have attracted considerable research interest owing to their combined merits of homogeneous and heterogeneous catalysts. However, the uniform and isolated active sites of SACs fall short in catalysing complex chemical processes that simultaneously involve multiple intermediates. In this Review, we highlight an emerging class of catalysts with adjacent binary active centres, which is called integrative catalytic pairs (ICPs), showing not only atomic-scale site-to-site electronic interactions but also synergistic catalytic effects. Compared with SACs or their derivative dual-atom catalysts (DACs), multi-interactive intermediates on ICPs can overcome kinetic barriers, adjust reaction pathways and break the universal linear scaling relations as the smallest active units. Starting from this active-site design principle, each single active atom can be considered as a brick to further build integrative catalytic clusters (ICCs) with desirable configurations, towards trimer or even larger multi-atom units depending on the requirement of a given reaction.

Origin of Magnetism in a Supposedly Nonmagnetic Osmium Oxide.

A supposedly nonmagnetic 5d^{1} double perovskite oxide is investigated by a combination of spectroscopic and theoretical methods, namely, resonant inelastic x-ray scattering, x-ray absorption spectroscopy, magnetic circular dichroism, and multiplet ligand-field calculations. We found that the large spin-orbit coupling admixes the 5d t_{2g} and e_{g} orbitals, covalency raises the 5d population well above the nominal value, and the local symmetry is lower than O_{h}. The obtained electronic interactions account for the finite magnetic moment of Os in this compound and, in general, of 5d^{1} ions. Our results provide direct evidence of elusive Jahn-Teller distortions, hinting at a strong electron-lattice coupling.

Electrochemically Active MoO3/TiN Sulfur Host Inducing Dynamically Reinforced Built-in Electric Field for Advanced Lithium-Sulfur Batteries.

Although various electrocatalysts have been developed to ameliorate the shuttle effect and sluggish Li-S conversion kinetics, their electrochemical inertness limits the sufficient performance improvement of lithium-sulfur batteries (LSBs). In this work, an electrochemically active MoO3/TiN-based heterostructure (MOTN) is designed as an efficient sulfur host that can improve the overall electrochemical properties of LSBs via prominent lithiation behaviors. By accommodating Li ions into MoO3 nanoplates, the MOTN host can contribute its own capacity. Furthermore, the Li intercalation process dynamically affects the electronic interaction between MoO3 and TiN and thus significantly reinforces the built-in electric field, which further improves the comprehensive electrocatalytic abilities of the MOTN host. Because of these merits, the MOTN host-based sulfur cathode delivers an exceptional specific capacity of 2520mA h g-1 at 0.1 C. Furthermore, the cathode exhibits superior rate capability (564mA h g-1 at 5 C), excellent cycling stability (capacity fade rate of 0.034% per cycle for 1200 cycles at 2 C), and satisfactory areal capacity (6.6mA h cm-2) under a high sulfur loading of 8.3mg cm-2. This study provides a novel strategy to develop electrochemically active heterostructured electrocatalysts and rationally manipulate the built-in electric field for achieving high-performance LSBs.

Base Metals Induced Oxygen Migration and Adjustable Performance in Multifunctional Oxide Heterojunction Devices

AbstractThe chemical and electronic interactions at metal/oxide heterojunctions is pivotal in determining the electronic properties of oxide devices utilized in microelectronics, catalysis, and photovoltaic systems. In this study, interfacial oxidation migrations within a model heterostructure system, consisting of a La0.7Sr0.3MnO3 film overlaid by various metallic (Ti, Al, Cu, Ag, and Au) ultrathin layers are systematically investigated. It is experimentally demonstrated that at elevated deposition temperature, the oxygen‐active ultrathin overlayers of base metals such as Ti and Al significantly derive oxygen from the underlying La0.7Sr0.3MnO3 film, inducing a perovskite to brownmillerite phase transition in the underlying functional oxide film. Conversely, no structural transitions are observed for La0.7Sr0.3MnO3 film when it is capped by noble metals (Au, Ag), which possess relative high oxidation formation energy. These observations are crucial for the development of novel crystalline and electronic architectures in metal/oxide heterostructures, offering a refined approach to modulate interfacial reactivity without compromising the functionality of oxide‐based heterojunction devices.

Numerical tools for simulating low-energy electron interactions in experimental nanodosimetry applications

Radiation damages to genes and cells occur at the DNA level, and therefore they are directly related to the spatial distribution of events caused by radiation at nanometer scale. Nanodosimetry introduces new quantities to correlate the initial features of radiation interactions and the likelihood of late radiobiological effects by means of Monte Carlo codes and, experimentally, with gas-detectors operating at low pressure.Within this context, the aim of this work is to develop a numerical approach based on the implementation of different simulation tools to accurately describe the low energy electron transport processes within nanodosimetric devices. This approach was directly applied to perform a proof-of-concept study of the response of the electron collector of the STARTRACK nanodosimeter. Garfield++ was used to simulate the primary track structure of 5.8 MeV He-4 particles, while COMSOL Multiphysics was used to model the geometry and the electrostatic field of the electron collector. Available experimental data, measured with the STARTRACK nanodosimeter, were used to validate Garfield++ nanodosimetric spectrum before proceeding with the simulation of the electron transport stage in the drift volume, again performed with Garfield++. In order to verify the performance and reliability of the implemented codes, the nanodosimetric distributions were studied with the threefold objective of characterizing the time, space, and energy distributions of particles collected at the end of the drift volume. These results can offer a valuable insight into the overall working principle of nanodosimeters: this understanding can be pivotal in optimizing and refining the design of such devices, ultimately extending their effectiveness in particle track characterization during radiation therapy.

High-Efficiency NO conversion via In-Situ grown covalent organic framework on g-C3N4 nanosheets with Single-Atom platinum photocatalyst

This study presents a chemically bonded Pt/TP-BPY-CN/g-C3N4 composite photocatalyst created through an in-situ growth method via Schiff base reaction between g-C3N4 and aldehyde-functionalized TP-BPY-COF. The −H-C-N-H- bonds formed at the g-C3N4 and TP-BPY-COF interface significantly boost electron communication, thereby substantially enhancing transfer efficiency between these two constituents. Besides, single-atom platinum incorporation via coordination establishes a Pt2+/Pt4+ redox cycle, aiding both oxidation and reduction of nitric oxide (NO). Consequently, the Pt/40TPBPY-CN composite achieves 65.3 % NO conversion, with almost 100 % oxidation selectivity towards NO3–. In-situ XPS analysis confirms the robust electron communication between TP-BPY-COF and g-C3N4 facilitated by −H-C-N-H- bonds, and the redox transformation between Pt2+ and Pt4+. In addition, DFT calculation provides a deeper insight into photocatalytic oxidation and reduction pathways, confirming an inhibition of N2 desorption. This research underscores the benefits of chemically bonded heterostructures for improved electronic interactions and highlights the efficacy of bifunctional single-atom platinum in photocatalysis.

Density functional theory and spectroscopic analysis of stigmasterol from Garcinia wightii: Deciphering its inhibitory potential against drug-resistant tuberculosis via insilico molecular docking and molecular dynamics simulations

This study investigates the molecular structure and electronic properties of stigmasterol, isolated from Garcinia wightii, using density functional theory (DFT) alongside experimental techniques including FT-IR, FT-Raman, UV–Vis, 1H and 13C NMR spectroscopy. Theoretical predictions are compared with experimental results, facilitated by vibrational energy distribution analysis for unambiguous vibrational wavenumber assignments. Natural bond orbitalanalyzes reveal donor-acceptor bond energies and electron densities, while Fukui functions identify reactive sites susceptible to electrophilic and nucleophilic attacks. Electronic properties are further explored through various analyzes, unveiling reactive surface sites. Non-covalent interactions are examined using reduced density gradient analysis. Assessment of absorption, distribution, metabolism, and excretion attributes aids in drug discovery efforts. Molecular docking studies against 20 target proteins for antitubercular screening show a stable glide score of -9.52 kcal/mol for the protein 4FDO (Mycobacterium tuberculosis DprE1 in complex with CT319). Molecular dynamics simulations over 100 ns indicate the stability of the ligand-protein complex, suggesting its potential as an antituberculosis agent. Stigmasterol's structural, vibrational, electronic, and topological properties are thoroughly investigated, revealing its ring skeleton with a flexible isooctyl side chain, adhering to C1 point group symmetry. Steric and stereo electronic interactions play crucial roles in conformation and binding to target proteins. Theoretical and experimental analyzes align, confirming the compound's bioactive properties. This comprehensive investigation underscores stigmasterol's potential as a tuberculosis treatment option, providing valuable insights into its structural characteristics and therapeutic possibilities.

Polymer-Gel-Derived PbS/C Composite Nanosheets and Their Photoelectronic Response Properties Studies in the NIR

Non-conjugated polymer-derived functional nanocomposites are one of the important ways to develop multifunctional hybrids. By increasing the degree of crosslinking, their photophysical properties can be improved. PbS is a class of narrow bandgap infrared active materials. To avoid aggregation and passivation of the surface defects of PbS nanomaterials, a large number of organic and inorganic ligands are usually used. In this study, PbS/C composite nanosheets were synthesized with Pb2+ ion-crosslinked sodium alginate gel by one-pot carbonization. The resulting nanosheets were coated on untreated A4 printing paper, and the electrodes were the graphite electrodes with 5B pencil drawings. The photocurrent signals of the products were measured using typical 650, 808, 980, and 1064 nm light sources. The results showed that the photocurrent switching signals were effectively extracted in the visible and near-infrared regions, which was attributed to the mutual passivation of defects during the in situ preparation of PbS and carbon nanomaterials. At the same time, the resulting nanocomposite exhibited electrical switching responses to the applied strain to a certain extent. The photophysical and defect passivation mechanisms were discussed based on the aggregation state of the carbon hybrid and the interfacial electron interaction. This material would have potential applications in broadband flexible photodetectors, tentacle sensors, or light harvesting interdisciplinary areas. This study provided a facile approach to prepare a low-cost hybrid with external stimulus response and multifunctionality. These results show that the interfacial charge transfer is the direct experimental evidence of interfacial interaction, and the regulation of interfacial interaction can improve the physical and chemical properties of nanocomposites, which can meet the interdisciplinary application. The interdisciplinary and application of more non-conjugated polymer systems in some frontier areas will be expanded upon.

Effect of A-site disorder and reduced grain size on low temperature resistivity minima and magnetoresistance behaviour in Nd0.7-xGdxSr0.3MnO3 (0 ≤ x ≤ 0.3)

ABSTRACT The present work provides a detailed investigation of the electronic- and magneto-transport properties of bulk and nanostructured Nd0.7-xGdxSr0.3MnO3 (x = 0, 0.1, 0.2 and 0.3) polycrystalline manganites. We have specially addressed the issue of the observed minimum in the temperature dependent resistivity of these manganites in the low temperature regime (<50 K). It is observed that increase of A-site disorder due to progressive substitution of Gd and decrease of grain size enhances the observed resistivity minima. Different theoretical models have been employed to analyze the resistivity data in the low temperature regime. It has been established that the quantum interference effect due to electron–electron interaction, most likely, is the dominant factor of the observed resistivity minimum and upturn in resistivity in the lower temperature regime. The effect of phase separation is also found to play a key role in the electronic-transport of the materials. Further the magnetoresistance is found to increase with the increase of Gd concentration as well as with the decrease of grain size in the low temperature regime. The origin of magnetoresistance has been critically analyzed.

Construction of iron-doped nickel cobalt phosphide nanoparticles via solvothermal phosphidization and their application in alkaline oxygen evolution

Multi-metallic phosphides offer the possibility to combine the strategies of surface reconstruction, electronic interaction and mechanistic pathway tuning to achieve high electrocatalytic oxygen evolution activity. Here, iron-doped nickel cobalt phosphide nanoparticles (FexCoyNi2-x-yP) with the crystalline NiCoP phase are for the first time synthesized by the solvothermal phosphidization method via the reaction between metal–organic frameworks and white phosphorus. When used to electrochemically catalyze oxygen evolution reaction (OER), the Fe0.4Co0.8Ni0.8P supported by nickel foam requires only 248 mV overpotential to achieve 10 mA cm−2 current densities, and is robust towards the long-term OER in 1 M KOH. The higher number of electrochemically active sites can account for the good OER activity, along with the improved intrinsic activity which is caused by the electron interaction that optimizes the adsorption energy of hydroxyl intermediates, and that increases the acidity of high-valent metal centers. The OER mechanistic pathway involves both adsorbate and lattice oxygen. Surface conversion is observed after OER in alkaline solution, and metal phosphide layer transforms to metal oxides and (oxy)hydroxides.

Bose–Einstein distribution temperature features of quasiparticles around magnetopolaron in Gaussian quantum wells of alkali halogen ions

Abstract We have applied strong coupling unitary transformation method combined with Bose–Einstein statistical law to investigate magnetopolaron energy level temperature effects in halogen ion crystal quantum wells. The obtained results showed that under magnetic field effect, magnetopolaron quasiparticle was formed through the interaction of electrons and surrounding phonons. At the same time, magnetopolaron was influenced by phonon temperature statistical law and important energy level shifts down and binding energy increases. This revealed that lattice temperature and magnetic field could easily affect magnetopolaron and the above results could play key roles in exploring thermoelectric conversion and conductivity of crystal materials.