Electron-electron Interaction Research Articles

Detailed Reaction Mechanism of Anthracene‐Bridged bis‐(3‐Pyridiniumboronic Acid) Chemosensor with D‐Glucose

AbstractDetailed reaction mechanisms of 4‐(N‐methyl)pyridinium boronic acid (1) and anthracene‐bridged bis(pyridinium boronic acid) compounds (diboronic acids 2 and 3) with D‐glucose were kinetically investigated in aqueous methanolic solutions. The crystal structure of diboronic acid 3 was determined using X‐ray crystallography. The pKa values of the two boronic acid moieties of diboronic acid (2 or 3) differed by one unit, indicating electronic interactions between the two boronic acid moieties. The kinetics of the reaction of boronic acid 1 with D‐glucose showed that both trigonal boronic acid and tetrahedral boronate ions were reactive with D‐glucose. UV‐Vis spectrophotometry and 1H NMR spectrometry of the reactions of phenylboronic acid with some model compounds of D‐glucose showed that the reactive moiety of α‐D‐glucofuranose towards phenylboronic acid was not the 1,2‐diol site, but the 3,5,6‐triol site. In the reactions of diboronic acids 2 and 3 with D‐glucose, the 3,5,6‐triol site of α‐D‐glucofuranose reacts first with one of the two equivalent boronic acid moieties of diboronic acid to form a 3,5‐bicoordinate intermediate as a rate‐determining step, followed by the reaction of the 1,2‐diol site of α‐D‐glucofuranose with another boronic acid moiety of diboronic acid to form the final 1,2 : 3,5‐tetracoordinate cyclic compound as a fast step.

Polarized Ultrathin BN Induced Dynamic Electron Interactions for Enhancing Acidic Oxygen Evolution.

Developing ruthenium-based heterogeneous catalysts with an efficient and stable interface is essential for enhanced acidic oxygen evolution reaction (OER). Herein, we report a defect-rich ultrathin boron nitride nanosheet support with relatively independent electron donor and acceptor sites, which serves as an electron reservoir and receiving station for RuO2, realizing the rapid supply and reception of electrons. Through precisely controlling the reaction interface, a low OER overpotential of only 180 mV (at 10 mA cm-2) and long-term operational stability (350 h) are achieved, suggesting potential practical applications. In situ characterization and theoretical calculations have validated the existence of a localized electronic recycling between RuO2 and ultrathin BN nanosheets (BNNS). The electron-rich Ru sites accelerate the adsorption of water molecules and the dissociation of intermediates, while the interconnection between the O-terminal and B-terminal edge establishes electronic back-donation, effectively suppressing the over-oxidation of lattice oxygen. This study provides a new perspective for constructing a stable and highly active catalytic interface.

Strong electronic metal-support interactions as a strategy for boosting selective hydrogenation of resorcinol to 1,3-cyclohexanedione

Strong electronic metal-support interactions (EMSIs) present in supported metal catalysts play a crucial role in determining their catalytic performances. In this study, we demonstrate the successful utilization of nanosized TiO2 (∼8 nm) as a carrier to achieve highly dispersed Pd clusters (∼0.59 nm) with robust EMSIs, even at a high Pd loading of 5 wt%. The presence of surface defects in nanosized TiO2 facilitates the anchoring of Pd clusters onto the support surface, leading to enhanced EMSIs between TiO2 and Pd. The prepared Pd/TiO2 catalyst delivers drastically improved catalytic property in the hydrogenation of resorcinol (RES), achieving >99 % conversion and >99 % selectivity towards 1,3-cyclohexanedione (1,3-CHD) within 60 min at 2 MPa hydrogenation pressure and 373 K. This performance is superior to that of Pd nanoparticles on TiO2 support with a larger particle size of ∼200 nm, which only achieves 80 % conversion and 37 % selectivity to 1,3-CHD. Both experimental data and theoretical calculations confirm that TiO2 donates electrons to the Pd clusters, thereby enhancing the hydrogenation properties of RES. Specifically, the electron-deficient TiO2 favors the adsorption and activation of phenoxy anion, while the electron-enriched Pd induces a nonplanar conformation of the adsorbed RES molecules and facilitates the electrophilic attack of adsorbed hydrogen on RES by weakening the strength of hydrogen adsorption. Furthermore, the Pd/TiO2 catalyst exhibits excellent recyclability, maintaining its efficiency over 7 cycles, attributed to the stabilizing effect of nanosized TiO2 on Pd clusters. The simple design strategy presented in this work enables the development of supported metal catalysts with significant EMSIs and is expected to attract more attention in future research.

Synthesis and electronics of donor–accepter linear arrays comprising anthracene bisimide with butadiynylene spacers

Abstract To further explore the π-conjugated systems of anthracene bisimide (ABI) and investigate their electronic properties, we synthesized donor–accepter linear arrays. These arrays consist of an ABI unit as the accepter and a 9,10-anthrylene unit as the donor, linked by a butadiynylene spacer. We constructed these donor–accepter arrays through Hay coupling of the corresponding 9,10-diethynylABI derivative with a 9,10-diethynylanthracene derivative. Theoretical calculations and electronic spectra analysis were employed to compare the photophysical properties of these compounds with those of their acetylene analogs. Moreover, we evaluated the intramolecular electronic interactions between the ABI and anthrylene units, focusing on the effects of the butadiynylene spacer and array sequences.

Rhombohedral platinum-copper intermetallic compound: A high phosphate tolerance electrocatalyst for HT-PEMFC

In high-temperature proton exchange membrane fuel cells (HT-PEMFC), phosphate anions act as a poisonous 'spectator species', binding strongly to the Pt surface through PtO bonds similarly to O2. This blocks the Pt active sites, resulting in slow ORR kinetics. Herein, we synthesized ultrafine L11-PtCu intermetallic compound nanoparticles (O-PtCu/S-C) loaded on an S-doped carbon support with an average size of about 3 nm through wet impregnation followed by hydrogen annealing, which showed high resistance to phosphate poisoning. The introduction of S notably improved the metal-support interaction and prevented particle growth during annealing, which is beneficial for the uniform distribution of nanoparticles and prevents detachment and agglomeration during ADT. The pronounced Cu-Pt electronic interaction in O-PtCu/S-C induced electron transfer from Cu to Pt, which effectively modified the electronic structure of Pt and weakened the adsorption energy of phosphate anions on the catalyst surface. In addition, the phosphate poisoning test results from both room temperature RDE and high-temperature RDE demonstrate that O-PtCu/S-C possesses excellent phosphate tolerance, superior ORR activity, and remarkable stability. It exhibits a superior peak power density of 800.5 mW cm−2 in 160°C H2-O2 HT-PEMFC with Pt loading of 0.5 mg cm−2. This research offers a novel approach to designing phosphate-resistant electrocatalysts for HT-PEMFC.

Single-phase ruthenium-based oxide with dual-atoms induced bifunctional catalytic centers enables highly efficient rechargeable Zn-air batteries

Composite strategies for constructing dual-atom sites at the hetero-interface provide considerable prospects for designing efficient bifunctional oxygen catalysts. Given the insufficient interface site and the instability of the phase interface, we need to develop more efficient strategies for efficiently utilizing the dual-atom site. Here, we report a doping strategy to construct abundant dual-atom sites in single-phase oxide catalysts. Ru/Mn dual-atom bond formation enables electronic interaction between Ru and Mn, which reduces the oxidation state of Ru sites and meanwhile constructs electron-rich states of Mn sites. DFT calculation was further applied to explore the reaction mechanism. We found that Mn and Ru atoms serve as oxygen reduction and oxygen evolution reaction catalytic sites respectively to facilitate oxygen adsorption and OH* desorption. More importantly, co-adsorption of OOH* on Mn/Ru dual sites can greatly enhance oxygen reduction activity. The resulting Mn-RuO2 catalyst exhibits an ultra-low ORR/OER overpotential of just 0.65 V, substantially lower than RuO2 and MnOx. Remarkably, Mn-RuO2 also demonstrates excellent stability, with minimal ORR decay after repeated OER cycling. Rechargeable zinc-air batteries using Mn-doped RuO2 achieve super-durability for 2000 cycles with a final energy efficiency retention of 87.5 %.

In-situ growth 2D Fe2P nanosheets on the surface of 1D Cd0.9Zn0.1S nanorods for remarkably improved photocatalytic H2 evolution

Loading cocatalysts can effectively reduce the hydrogen production overpotential and provide additional catalytic sites. Fe2P, with abundant active sites, low hydrogen evolution overpotential, is regarded as a promising cocatalyst to replace the noble metals. Fe2P nanosheets were grown in situ on the surface of Cd0.9Zn0.1S nanorods to form unique 2D/1D structure, which was designed to enlarge the interface contact between them. The maximum hydrogen evolution rate was as high as 38.48 mmol h−1 g−1, which was even higher than that of noble metal Pt modified Cd0.9Zn0.1S. The results of characterization and theoretical computation demonstrated that the electronic interaction existed between Fe2P and Cd0.9Zn0.1S, and Fe2P as cocatalyst collected electrons to facilitate the transfer and separation of electrons and holes. This work investigated the transfer process of photogenerated carriers and revealed the photocatalytic mechanism through a combination of theoretical calculation and experimental characterization.

Highly efficient nitrogen fixation over S-scheme heterojunction photocatalysts with enhanced active hydrogen supply.

Photocatalytic N2 fixation is a promising strategy for ammonia (NH3) synthesis; however, it suffers from relatively low ammonia yield due to the difficulty in the design of photocatalysts with both high charge transfer efficiency and desirable N2 adsorption/activation capability. Herein, an S-scheme CoSx/ZnS heterojunction with dual active sites is designed as an efficient N2 fixation photocatalyst. The CoSx/ZnS heterojunction exhibits a unique pocket-like nanostructure with small ZnS nanocrystals adhered on a single-hole CoSx hollow dodecahedron. Within the heterojunction, the electronic interaction between ZnS and CoSx creates electron-deficient Zn sites with enhanced N2 chemisorption and electron-sufficient Co sites with active hydrogen supply for N2 hydrogenation, cooperatively reducing the energy barrier for N2 activation. In combination with the promoted photogenerated electron-hole separation of the S-scheme heterojunction and facilitated mass transfer by the pocket-like nanostructure, an excellent N2 fixation performance with a high NH3 yield of 1175.37 μmol g-1 h-1 is achieved. This study provides new insights into the design of heterojunction photocatalysts for N2 fixation.

Electron-rich ruthenium nanoparticles on nitrogen-doped carbon for the efficient catalytic oxidation of 5-hydroxymethylfurfural into 2,5-furandicarboxylic acid

Modulating the electronic structure of metal nanoparticles (NPs) demonstrates to be useful for the optimization of the catalytic performance. Herein, electron-sufficient ruthenium NPs were successfully constructed on a nitrogen-doped carbon support (Rux-NC), which displayed excellent catalytic activity for the oxidation of 5-hydroxymethylfurfural (HMF) into 2,5-furandicarboxylic acid (FDCA). Especially, a high FDCA yield of 97% was implemented over Ru2.0/NC catalyst in water. The FDCA productivity in this case is also as high as 4.8 molFDCA‧molRu−1‧h−1, which value exceeds most of the previous reported Ru-based catalysts for the production of FDCA. It has been disclosed that the Ru2.0/NC was endowed with high N content and abundant electron-rich Ru0 NPs evoked by the electronic interactions between the NC support the Ru NPs. These facts greatly contribute to the activation of O2, and accelerate the oxidation both of the hydroxymethyl and aldehyde groups of HMF to the carboxyl one. This work provides new understanding for the development of effective Ru-based catalysts for the catalytic oxidation reactions by the electronic structure regulation strategy.

Tailoring the cryogenic magnetism and magnetocaloric effect from Zr substitution in EuTiO3 perovskite

Refrigeration in the liquid helium temperature range provides vital technological support for many scientific frontiers and engineering technologies. The considerable magnetocaloric effect (MCE) makes EuTiO3 a potential candidate for magnetic refrigeration near liquid helium temperature. More interestingly, the magnetic transition from antiferromagnetism to ferromagnetism offers the possibility to tailor the magnetism and improve the MCE of this magnetic system. In this study, the magnetic properties and MCE of EuTi0.875Zr0.125O3 were systematically investigated by first-principles calculation and experiments. The substitution of Zr induces a significant lattice expansion and alters the electronic interactions, leading to a dominance of ferromagnetism in the compound. Remarkable low-field MCE performance has been achieved attributed to the enhanced ferromagnetism and low saturation field. Under the field change of 0–1 T, the maximum magnetic entropy change (−ΔSMmax) and adiabatic temperature change (ΔTadmax) are 17.9 J kg−1 K−1 and 6.1 K, respectively. It is worth noting that the −ΔSMmax of EuTi0.875Zr0.125O3 reaches 10.3 J kg−1 K−1 for a field change of 0–0.5 T, making it one of the best magnetocaloric materials ever reported operating in the liquid helium temperature range.

Tailoring the Electronic Metal-Support Interactions in Supported Silver Catalysts through Al modification for Efficient Ethylene Epoxidation.

Metal-modified catalysts have attracted extraordinary research attention in heterogeneous catalysis due to their enhanced geometric and electronic structures and outstanding catalytic performances. Silver (Ag) possesses necessary active sites for ethylene epoxidation, but the catalyst activity is usually sacrificed to obtain high selectivity towards ethylene oxide (EO). Herein, we report that using Al can help in tailoring the unoccupied 3d state of Ag on the MnO2 support through strong electronic metal-support interactions (EMSIs), overcoming the activity-selectivity trade-off for ethylene epoxidation and resulting in a very high ethylene conversion rate (~100 %) with 90 % selectivity for EO under mild conditions (170 °C and atmospheric pressure). Structural characterization and theoretical calculations revealed that the EMSIs obtained by the Al modification tailor the unoccupied 3d state of Ag, modulating the adsorption of ethylene (C2H4) and oxygen (O2) and facilitating EO desorption, resulting in high C2H4 conversion. Meanwhile, the increased number of positively charge Ag+ lowers the energy barrier for C2H4(ads) oxidation to produce oxametallacycle (OMC), inducing the unexpectedly high EO selectivity. Such an extraordinary electronic promotion provides new promising pathways for designing advanced metal catalysts with high activity and selectivity in selective oxidation reactions.

Robustness of frictional anisotropy under high load due to self-folding

Friction anisotropy is not only related to macroscopic natural phenomena, but also closely involves the emerging field of nanotechnology. The previous strategies to achieve friction anisotropy requires delicate adjustment, which is difficult to achieve in method, or easy to disappear under large loads. Here, we report the outstanding robustness of frictional anisotropy caused by its own fold structure under high load. The frictional anisotropy is always larger than 200% between the armchair and zigzag direction of Se/Se interface under load up to 5.5 GPa and its maximum value reaches 325%. The frictional anisotropy between these two directions origins from the tremendous difference in charge density redistribution reflected only in direction perpendicular to interface, which is a novel method to quantitatively characterize friction from the perspective of electronic interaction. The load-induced weakening of friction anisotropy derives from the sudden change in chemical interactions between atoms around interface. The exploring of extreme frictional anisotropy caused by its own structure is not only helpful for a comprehensive understanding of frictional anisotropy behavior, but also contributes to the construction of nanodevices required the friction anisotropy to achieve, such as mechanical logic gates.

Nonlinear electron scattering by electrostatic waves in collisionless shocks

We present a theoretical analysis of electron pitch-angle scattering by ion-acoustic electrostatic fluctuations present in the Earth's bow shock and, presumably, collisionless shocks in general. We numerically simulate electron interaction with a single wave packet to demonstrate the scattering through phase bunching and phase trapping and quantify electron pitch-angle scattering in dependence on the wave amplitude and wave normal angle to the local magnetic field. The iterative mapping technique is used to model pitch-angle scattering of electrons by a large number of wave packets, which have been reported in the Earth's bow shock. Assuming that successive electron scatterings are not correlated, we revealed that the long-term dynamics of electrons is diffusive. The diffusion coefficient depends on the ratio $\varPhi _0/W$ between the wave packet amplitude and electron energy, $D\propto (\varPhi _0/W)^{\nu }$ . A quasi-linear scaling ( $\nu \approx 2$ ) is observed for sufficiently small wave amplitudes, $\varPhi _0\lesssim 10^{-3}W$ , while the diffusion is nonlinear ( $1<\nu <2$ ) above this threshold. We show that pitch-angle diffusion of ${\lesssim }1$ keV electrons in the Earth's bow shock can be nonlinear. The corresponding diffusion coefficient scales with the intensity $E_{w}^{2}$ of the electrostatic fluctuations in a nonlinear fashion, $D\propto E_{w}^{\nu }$ with $\nu <2$ , while its expected values in the Earth's bow shock are $D\sim 0.1\unicode{x2013}100$ $(T_{e}/W)^{\nu -1/2}\,{\rm rad}^{2}\,{\rm s}^{-1}$ . We speculate that in the Earth's quasi-perpendicular bow shock the stochastic shock drift acceleration mechanism with pitch-angle scattering provided by the electrostatic fluctuations can contribute to the acceleration of thermal electrons up to approximately 1 keV. The potential effects of a finite perpendicular coherence scale of the wave packets on the efficiency of electron scattering are discussed.

A Coherent Pd–Pd16B3 Core–Shell Electrocatalyst for Controlled Hydrogenation in Nitrogen Reduction Reaction

AbstractThe manipulation of surface catalytic sites has rarely been explored for metal borides, and the subsurface effects on the electrocatalytic activity of the nitrogen reduction reaction (NRR) remain unknown. Herein, this work develops a core–shell nanoparticle catalyst with a Pd core that ensures high electron transfer rates and an Pd16B3 atomical shell that possess tunable active sites for regulating the NRR. The atomic structural evolution from Pd to Pd16B3 is investigated by precisely controlling the B atom diffusion, molecular rearrangement, and d–sp orbital hybridization. Pd/Pd16B3 core–shell nanocrystals exhibit an exceptional NRR performance with a high NH3 Faradaic efficiency of 30.8%, which is superior to those of pristine Pd (1.2%) and B‐doped Pd (4.8%) under identical conditions, and a yield rate of 0.81 µmol h−1 cm−2. This work discovers that the Pd16B3 shell could promote the NRR selectivity by separating the separating the hydrogen evolution reaction proceeded on hole sites and NRR proceeded on bridge sites, and the Pd core could provide the excellent conductivity to Pd16B3 shell through regulated electron interactions. Consequently, the controlled chemical ordering of palladium boride on palladium surfaces provides insight into the synthesis of advanced NRR electrocatalysts.

Genesis of legal regulation of the web and the model of the Metaverse electronic jurisdiction

The study examines the transformation of scientific views and approaches to the problem of expediency and necessity of legal regulation of public relations, emerging from the evolution of the world system of public electronic resources in the transmission of information and Internet data from Web 1.0, Web 2.0 to Web 3.0. The stages of formation of the role and place of electronic jurisdiction in public relations are also investigated. Legal regulation of modern relations in virtual and augmented reality environments with the use of Web 3.0 technologies is not available today. At the same time, there are precedents for the application of certain provisions of analogue law to address legal uncertainties in the virtual environment, such as establishing ownership of virtual non-property assets, buying/selling of virtual non-property assets, liability for misappropriation of virtual non-property assets, etc. Obviously, the problem of legal regulation by the rules of analogue law in the virtual environment cannot be fully addressed. The solution to this problem is possible by creating a comprehensive e-jurisdiction and developing the Metaverse Grand Charter of Laws to regulate public relations in the meta-universe and to establish new branch of e-law. Given the urgency of the problem, the model of e-jurisdiction Grand Charter of Laws Metaverse is proposed. The model of complex electronic jurisdiction of Metaverse will allow to create basic conceptual apparatus, doctrinal and regulatory and legal concepts, to define objects and subjects of legal relations in Metaverse, to establish the basic forms of legal relations and mutual relations in Metaverse. This, in turn, will be the basis for reforming analogue legislation, partial interoperability in the digital environment and the development of new regulations in various areas of law and will stimulate the establishment of new e-jurisdiction. The study proposes the construction and basic elements of electronic jurisdiction, mechanisms for the separation of electronic offences and interaction with analogue jurisdictions. E-jurisdiction of the Metaverse Grand Charter of Laws will provide legal regulation of public relations both directly in Metaverse and in public relations related to the analogue and electronic world.

Spatially and Temporally Resolved Dynamic Response of Co-Based Composite Interface during the Oxygen Evolution Reaction.

Interfacial interaction dictates the overall catalytic performance and catalytic behavior rules of the composite catalyst. However, understanding of interfacial active sites at the microscopic scale is still limited. Importantly, identifying the dynamic action mechanism of the "real" active site at the interface necessitates nanoscale, high spatial-time-resolved complementary-operando techniques. In this work, a Co3O4 homojunction with a well-defined interface effect is developed as a model system to explore the spatial-correlation dynamic response of the interface toward oxygen evolution reaction. Quasi in situ scanning transmission electron microscopy-electron energy-loss spectroscopy with high spatial resolution visually confirms the size characteristics of the interface effect in the spatial dimension, showing that the activation of active sites originates from strong interfacial electron interactions at a scale of 3 nm. Multiple time-resolved operando spectroscopy techniques explicitly capture dynamic changes in the adsorption behavior for key reaction intermediates. Combined with density functional theory calculations, we reveal that the dynamic adjustment of multiple adsorption configurations of intermediates by highly activated active sites at the interface facilitates the O-O coupling and *OOH deprotonation processes. The dual dynamic regulation mechanism accelerates the kinetics of oxygen evolution and serves as a pivotal factor in promoting the oxygen evolution activity of the composite structure. The resulting composite catalyst (Co-B@Co3O4/Co3O4 NSs) exhibits an approximately 70-fold turnover frequency and 20-fold mass activity than the monomer structure (Co3O4 NSs) and leads to significant activity (η10 ∼257 mV). The visual complementary analysis of multimodal operando/in situ techniques provides us with a powerful platform to advance our fundamental understanding of interfacial structure-activity relationships in composite structured catalysts.

Anomalous electrons in a metallic kagome ferromagnet

Ordinary metals contain electron liquids within well-defined ‘Fermi’ surfaces at which the electrons behave as if they were non-interacting. In the absence of transitions to entirely new phases such as insulators or superconductors, interactions between electrons induce scattering that is quadratic in the deviation of the binding energy from the Fermi level. A long-standing puzzle is that certain materials do not fit this ‘Fermi liquid’ description. A common feature is strong interactions between electrons relative to their kinetic energies. One route to this regime is special lattices to reduce the electron kinetic energies. Twisted bilayer graphene1–4 is an example, and trihexagonal tiling lattices (triangular ‘kagome’), with all corner sites removed on a 2 × 2 superlattice, can also host narrow electron bands5 for which interaction effects would be enhanced. Here we describe spectroscopy revealing non-Fermi-liquid behaviour for the ferromagnetic kagome metal Fe3Sn2 (ref. 6). We discover three C3-symmetric electron pockets at the Brillouin zone centre, two of which are expected from density functional theory. The third and most sharply defined band emerges at low temperatures and binding energies by means of fractionalization of one of the other two, most likely on the account of enhanced electron–electron interactions owing to a flat band predicted to lie just above the Fermi level. Our discovery opens the topic of how such many-body physics involving flat bands7,8 could differ depending on whether they arise from lattice geometry or from strongly localized atomic orbitals9,10.

Tuning the electronic metal-carbon interactions in Lignin-based carbon-supported ruthenium-based electrocatalysts for enhanced hydrogen evolution reactions

Ruthenium (Ru) nanoparticles dispersed on carbon support are promising electrocatalysts for hydrogen evolution reaction (HER) due to strong electronic metal-carbon interactions (EMCIs). Defects engineering in carbon supports is an effective strategy to adjust EMCIs. We prepared nitrogen/sulfur co-doped carbon supported Ru nanoparticles (Ru@N/S-LC) using sodium lignosulfonate and urea as feedstocks. Intrinsic S dopants from sodium lignosulfonate create rich S defects, thus enhancing the EMCIs within Ru@N/S-LC, leading a faster electron transfer between Ru nanoparticles and N/S-LC compared with N-doped carbon supported Ru nanoparticles (Ru@N-CC). The resulting Ru@N/S-LC exhibits an enhanced work function and a down-shifted d-band center, inducing stronger electron capturing ability and weaker hydrogen desorption energy than Ru@N-CC. Ru@N/S-LC requires only 7 and 94 mV overpotential in acidic medium and alkaline medium to achieve a current density of 10 mA cm−2. Density Functional Theory (DFT) calculations were utilized to clarify the impact of sulfur (S) doping and the mechanism underlying the notable catalytic activity of Ru@N/S-LC. This study offers a perspective for utilizing the natural dopants of biomass to adjust the EMCIs for electrocatalysts.

Correlation-Induced Symmetry-Broken States in Large-Angle Twisted Bilayer Graphene on MoS2.

Strongly correlated states commonly emerge in twisted bilayer graphene (TBG) with "magic-angle" (1.1°), where the electron-electron (e-e) interaction U becomes prominent relative to the small bandwidth W of the nearly flat band. However, the stringent requirement of this magic angle makes the sample preparation and the further application facing great challenges. Here, using scanning tunneling microscopy (STM) and spectroscopy (STS), we demonstrate that the correlation-induced symmetry-broken states can also be achieved in a 3.45° TBG, via engineering this nonmagic-angle TBG into regimes of U/W > 1. We enhance the e-e interaction through controlling the microscopic dielectric environment by using a MoS2 substrate. Simultaneously, the width of the low-energy van Hove singularity (VHS) peak is reduced by enhancing the interlayer coupling via STM tip modulation. When partially filled, the VHS peak exhibits a giant splitting into two states flanked by the Fermi level and shows a symmetry-broken LDOS distribution with a stripy charge order, which confirms the existence of strong correlation effect in our 3.45° TBG. Our result demonstrates the feasibility of the study and application of the correlation physics in TBGs with a wider range of twist angle.

Heterointerface engineering of rhombic Rh nanosheets confined on MXene for efficient methanol oxidation

Although metallic rhodium (Rh) is regarded as a promising platinum-alternative anode catalyst of direct methanol fuel cell (DMFC), the conventional “particle-to-face” contact model between Rh and matrix largely limits the overall electrocatalytic performance due to their insufficient cooperative effects. Herein, we report a controllable and robust heterointerface engineering strategy for the bottom-up fabrication of rhombic Rh nanosheets in situ confined on Ti3C2Tx MXene nanolamellas (Rh NS/MXene) via a convenient stereoassembly process. This unique design concept gives the resulting 2D/2D Rh NS/MXene heterostructure intriguing textural features, including large accessible surface areas, strong “face-to-face” interfacial interactions, homogeneous Rh nanosheet distribution, ameliorative electronic structure, and high electronic conductivity. As a consequence, the as-prepared Rh NS/MXene nanoarchitectures exhibit exceptional electrocatalytic methanol oxidation properties in terms of a large electrochemically active surface area of 126.2 m2 g−1Rh, a high mass activity of 1056.9 mA mg−1Rh, and a long service life, which significantly outperform those of conventional particle-shaped Rh catalysts supported by carbon black, carbon nanotubes, reduced graphene oxide, and MXene matrixes as well as the commercial Pt nanoparticle/carbon black and Pd nanoparticle/carbon black catalysts with the same noble metal loading amount. Density functional theory calculations further demonstrate that the direct electronic interaction at the well-contacted 2D/2D heterointerfaces effectively enhances the adsorption energy of Rh nanosheets and induces a left shift of the d-band center, thereby making the Rh NS/MXene configuration suffer less from CO poisoning. This work highlights the importance of rational heterointerface design in the construction of advanced noble metal/MXene electrocatalysts, which may provide new avenues for developing the next-generation DMFC devices.