Adjacent Metal Research Articles

Selective Photocatalytic Oxidative Coupling of Methane via Regulating Methyl Intermediates over Metal/ZnO Nanoparticles

AbstractMethane conversion to higher hydrocarbons requires harsh reaction conditions due to high energy barriers associated with C−H bond activation. Herein, we report a systematic investigation of photocatalytic oxidative coupling of methane (OCM) over transition‐metal‐loaded ZnO photocatalysts. A 1 wt % Au/ZnO delivered a remarkable C2‐C4 hydrocarbon production rate of 683 μmol g−1 h−1 (83 % C2‐C4 selectivity) under light irradiation with excellent photostability over two days. The metal type and its interaction with ZnO strongly influence the selectivity toward C−C coupling products. Photogenerated Zn+‐O− sites enable CH4 activation to methyl intermediates (*CH3) migrating onto adjacent metal nanoparticles. The nature of the *CH3‐metal interaction controls the OCM products. In the case of Au, strong d‐σ orbital hybridization reduces metal‐C−H bond angles and steric hindrance, thereby enabling efficient methyl coupling. Findings indicate the d‐σ center may be a suitable descriptor for predicting product selectivity during OCM over metal/ZnO photocatalysts.

Optimization sulfur doping of electronic structure with metal active center for defect-rich FeCo bimetallic hydroxyl oxide catalysts

Defect engineering is an effective method to tune electronic states, which can provide active sites for electrocatalytic reactions. Herein, a highly efficient sulfur-doped bimetallic hydroxyl oxide (FeCo/Vc-S) has been synthesized by a two-step hydrothermal reaction, which has the rich defective and amorphous phases. The low coordination number of Co in X-ray absorption fine structure (XAFS) analysis further confirms the Co center is the active center, while Fe plays a role in optimizing the electronic structure of active Co species. Meanwhile, abundant oxygen vacancies and metal defects are also found in the material, which greatly enhances the adsorption and desorption efficiency of × OOH. Moreover, density functional theory (DFT) shows that the addition of S atom alters the electron distribution of adjacent metal atoms, thus adjusting the electron distribution of the metal active site. These positive factors endow FeCo/Vc-S with excellent OER electrocatalytic performance, with an overpotential of only 255 mV and Tafel slope is 64.3 mV·dec−1 at a current density of 10 mA cm−2. This study provides a new route for the synthesis of bimetallic hydroxyl oxides, and also provides theoretical design for the identification of active centers and defection-rich catalysts.

Highly integrated, breathable, metalized phase change fibrous membranes based on hierarchical coaxial fiber structure for multimodal personal thermal management

The development of personal thermal management textile is of great significance to satisfy the individual thermal comfort in an energy saving manner. However, major challenges remain, such as the sacrificed permeability, and limited mechanical durability, hindering long-term wearing comfort and reliability. Herein, a breathable, integrated thermoregulating fibrous membrane combining photo/electrothermal conversion and energy storage/release performance was fabricated for all-weather, on-demand, personal thermal management. We have delicately constructed a hierarchically ordered coaxial fiber structure that assembled functional components together for a versatile platform, through facile coaxial electrospinning followed by polydopamine (PDA) assisted metal deposition techniques. Interestingly, the intermediate PDA layer not only favors homogeneous loading of Ag nanoparticles (AgNPs), but also facilitates the interfacial bonding of the adjacent metal layer and the phase change fiber substrate for a seamlessly integrated system with improved structural stability and robust electrical performance. As a result, benefiting from the hierarchical coaxial structure of individual fibers and the overall well-preserved porous structure, we have fabricated an highly integrated, breathable, metalized phase change fibrous membrane with admirable heat enthalpy of 101.1 J/g, decent solar heating capability (up to 63.2 °C at 100 mW/cm2), and low voltage-driven Joule heating performance (up to 76.8 °C at 3.5 V), which exhibited a broad application prospect in next-generation wearable personal thermal management.

Study of oxygen reduction reaction on binuclear-phthalocyanine with Fe-Fe, Co-Co, and Fe-Co dual-atom-active sites using density functional theory

Although the N4-macrocyclic ligands have been used to develop single-atom catalysts (SACs), their utilization for the construction of dual-atom catalysts (DACs) for electrocatalytic oxygen reduction reaction (ORR) is poorly investigated. Herein, a binuclear phthalocyanine (bN-Pc) was explored as a theoretical model for the construction of FeFe-bN-Pc, CoCo-bN-Pc, and FeCo-bN-Pc dual-atom-site configurations and their ORR activity along with mechanisms were investigated systematically in alkaline media, using density functional theory (DFT) calculations. The results indicated that the dual-atom-bN-Pc models, having close proximity between adjacent metals, invited individual O-atom of O2 for coordination on both sites, forming a cis-bridged-O2 adduct. The Gibbs free energy studies showed that the decomposition of O2 on dual-atom sites was the rate-determining step, and the Fe-Co-bN-Pc had a lower energy barrier (0.591 eV) for this step as compared to Fe-Fe-bN-Pc (0.641 eV) and Co-Co-bN-Pc (0.692 eV), which justifies its stronger ORR performance. The synergistic effect of Fe-Co collaboration, the close proximity of Fe-Co, and the significant e- donation from the 3d-orbital of active sites into the *orbital of O2 can be attributed to this decrease in limiting the potential for the rate-determining step on Fe-Co-bN-Pc. For future ORR electrocatalysts, this work offers a scientific and engineering perspective on the construction of dual-atom active sites employing molecular moieties.

Emission of coherent THz magnons in an antiferromagnetic insulator triggered by ultrafast spin–phonon interactions

Antiferromagnetic materials have been proposed as new types of narrowband THz spintronic devices owing to their ultrafast spin dynamics. Manipulating coherently their spin dynamics, however, remains a key challenge that is envisioned to be accomplished by spin-orbit torques or direct optical excitations. Here, we demonstrate the combined generation of broadband THz (incoherent) magnons and narrowband (coherent) magnons at 1 THz in low damping thin films of NiO/Pt. We evidence, experimentally and through modeling, two excitation processes of spin dynamics in NiO: an off-resonant instantaneous optical spin torque in (111) oriented films and a strain-wave-induced THz torque induced by ultrafast Pt excitation in (001) oriented films. Both phenomena lead to the emission of a THz signal through the inverse spin Hall effect in the adjacent heavy metal layer. We unravel the characteristic timescales of the two excitation processes found to be < 50 fs and > 300 fs, respectively, and thus open new routes towards the development of fast opto-spintronic devices based on antiferromagnetic materials.

Adjacent diatomic Cu1N3/Mo1S2 entities decorated carbon nitride for markedly enhanced photocatalytic hydrogen generation

The regulation of the electronic structure of graphitic carbon nitride (CN) has been considered as one of the most promising methods to improve its photocatalytic efficiency. However, how to adjust effectively the electronic structure remains a great challenge. Herein, we pioneered a microwave-assisted solvothermal sulphidation strategy for the preparation of Cu1N3-linked Mo1S2 adjacent diatomic entities decorated CN (Cu1N3/Mo1S2/CN) through the enabled sulphidation around single Cu atom by the super hot spots owing to the localized surface plasmon resonance effect. The electronic structure of CN is regulated by the synergistic effect of the adjacent diatomic metal Cu and Mo, which not only makes the conduction band of the catalyst closer to the Fermi level, but also improves the charge transfer of CN. As a result, Under visible light irradiation and atmosphere conditions, the H2 generation rate (HER) of the Cu1N3/Mo1S2/CN catalyst reaches as high as 6.14 mmol g-1h−1, which is 85 times higher than that onbulk CN. It was highlighted that the introduced Cu1N3-linked Mo1S2 adjacent diatomic entities act as modulator to efficiently tune the electronic structure of the CN semiconductor, rather than as active sites, and for all samples, the deposited Pt is requested to act as active sites for H2 production. This work not only provides enlightenment for the development of an outstanding non-precious metals modified CN-based photocatalyst for solar hydrogen production, but also provides a new avenue for the design of diverse adjacent diatomic catalysts towards various transformations.

Controllable unidirectional magnetoresistance in ferromagnetic films with broken symmetry

Spin-related unidirectional magnetoresistance (UMR) exhibits nonreciprocal transport to either charge current or magnetization reversal, providing a potential application for direct electrical readout of in-plane magnetization using simple two-terminal geometry. To achieve such a UMR, it is usually believed that an adjacent heavy metal or other materials with strong spin-orbit coupling (SOC) as the spin polarizer is indispensable, leading to most efforts on multilayer structures rather than single-layer ferromagnetic films. Here, we report the observation of UMR in a single CoPt film by introducing a vertical composition gradient to break the structural inversion symmetry. Moreover, unlike conventional heavy-metal/ferromagnetic-metal bilayer films, the UMR in the CoPt film with a positive Co composition gradient is controllable as a function of current amplitude, which shows the decrease, sign reversal, and then enhancement with the increment of current density. These results reveal two competing UMR mechanisms with opposite signs in electrical current dependency, i.e., bulk Rashba effect induced by composition gradients and anomalous Nernst effect driven by a vertical temperature gradient. Our work provides a promising way to manipulate the UMR in a single ferromagnetic film with the combination of charge-spin conversion and magnetothermal effect.

Dual Metal Site Fe Single Atom Catalyst with Improved Stability in Acidic Conditions

Dual atom catalysts (DACs) not only retain uniform active sites and high atomic utilization efficiency as the single atom catalysts, but the two adjacent metal sites also cooperate and play a synergistic role to achieve additional benefits. However, the relationships connecting their dual-site synergistic effects on catalytic performance are not well rationalized due to limited pairs available from experiments. Herein, Fe/M dual sites supported by nitrogen doped carbon (Fe/M-N-C whereby M from 3 d–5 d electron containing transition metals) have been screened as an oxygen reduction reaction (ORR) catalyst. The results show that the absorption strength of ORR intermediates on four nitrogen coordinated metals is weaker than the three coordinated metals, which promotes favourable ORR activities. As a result, we recommended FeIr, FeRh, FeRu and FeOs as promising ORR catalysts. Ab initio molecular dynamic (AIMD) simulations suggest Fe/M-N-C (M = Ir, Rh, Ru and Os) catalysts with encouraging structural stability at room temperature. Furthermore, it is found that the nitrogen atoms in-between metals are vulnerable sites for proton attacking, yet the protonation process demands high energy, even under O2 atmosphere, which underlines good tolerance under acidic conditions. This work provides a broad understanding of Fe based catalyst and a new direction for catalytic design.

ZIF-derived non-bonding Co/Zn coordinated hollow carbon nitride for enhanced removal of antibiotic contaminants by peroxymonosulfate activation: Performance and mechanism

Co–Zn–N–C catalyst (MCZC) with neighboring Co and Zn pairs anchored on hollow carbon nitride was constructed by the direct etching of zeolitic imidazolate frameworks assembled with Co and Zn. Adequate characterizations and density functional theory (DFT) studies confirmed the successful construction of non-bonding Co and Zn pairs with enhanced electron transfer on Co sites by adjacent Zn sites. Based on the synergy of adjacent Co and Zn atom pairs, the MCZC/Perxymosulfate (PMS) system achieved 99.6% Tetracycline (TC) degradation in 24 min with a mineralization rate of 55.8% and PMS decomposition efficiency of 73.1%. DFT calculation based on the Fukui index identified the sites susceptible to attack by the active species. TC degradation pathways could be inferred, and reduced toxicity of intermediates was observed. This work provides new insights into the design of MOF-derived bimetallic catalysts and the importance of the interaction between adjacent metal active sites to catalytic performance.

Surface states of dual-atom catalysts should be considered for analysis of electrocatalytic activity

Experimentally well-characterized dual-atom catalysts (DACs), where two adjacent metal atoms are stably anchored on carbon defects, have shown some clear advantages in electrocatalysis compared to conventional catalysts and emerging single-atom catalysts. However, most previous theoretical studies directly used a pristine dual-atom site to analyze the electrocatalytic activity of a DAC. Herein, by analyzing 8 homonuclear and 64 heteronuclear DACs structures with ab initio calculations, our derived surface Pourbaix diagrams show that the surface states of DACs generally differ from a pristine surface at electrocatalytic operating conditions. This phenomenon suggests that the surface state of a DAC should be considered before analyzing the catalytic activity in electrocatalysis, while the electrochemistry-driven pre-adsorbed molecules generated from the liquid phase may either change the electronic properties or even block the active site of DACs. Based on these results, we provide a critical comment to the catalyst community: before analyzing the electrocatalytic activity of a DAC, its surface state should be analyzed beforehand.

Modulating the electronic structure of atomically dispersed Fe-Pt dual-site catalysts for efficient oxygen reduction reactions.

Atomically dispersed catalysts, with a high atomic dispersion of active sites, are efficient electrocatalysts. However, their unique catalytic sites make it challenging to improve their catalytic activity further. In this study, an atomically dispersed Fe-Pt dual-site catalyst (FePtNC) has been designed as a high-activity catalyst by modulating the electronic structure between adjacent metal sites. The FePtNC catalyst showed significantly better catalytic activity than the corresponding single-atom catalysts and metal-alloy nanocatalysts, with a half-wave potential of 0.90 V for the oxygen reduction reaction. Moreover, metal-air battery systems fabricated with the FePtNC catalyst showed peak power density values of 90.33 mW cm-2 (Al-air) and 191.83 mW cm-2 (Zn-air). By combining experiments and theoretical simulations, we demonstrate that the enhanced catalytic activity of the FePtNC catalyst can be attributed to the electronic modulation effect between adjacent metal sites. Thus, this study presents an efficient strategy for the rational design and optimization of atomically dispersed catalysts.

Symmetry or asymmetry: which one is the platform of nitrogen vacancies for alkaline hydrogen evolution.

Conventional nitrogen vacancies with a symmetric coordination of metal cations (i.e., M1-Nv-M1) play a crucial role in tuning the local environment of the metal sites in metal nitrides and improving their electrochemical activity in the hydrogen evolution reaction (HER). However, the symmetric Nv sites, which feature a uniform charge distribution on adjacent metal sites, suffer from sluggish water dissociation kinetics and a poor capability for hydrogen desorption. Here, we fabricated Cr-doped and Nv-rich Co4N nanorods grown on a Ni foam (Cr-Co4N-Nv/NF) with asymmetric Cr-Nv-Co sites to effectively catalyze hydrogen evolution under alkaline conditions, with a low overpotential of 33 mV at a current density of 10 mA cm-2 and a small Tafel slope of 37 mV dec-1. The experimental characterizations and theoretical simulations collectively reveal that the construction of asymmetric Cr-Nv-Co sites gives rise to the upshift of the d-band center, thus promoting water adsorption and activation. Moreover, asymmetric Nv sites allow a balance between hydrogen adsorption and desorption, which avoids the limited desorption process over the symmetric Co-Nv-Co sites.

Common-Mode Radiated Emission Analysis of Cable-Connected Printed Boards with Adjacent Metal Chassis by Imbalance Difference Model

Common-Mode Radiated Emission Analysis of Cable-Connected Printed Boards with Adjacent Metal Chassis by Imbalance Difference Model

Rational Positioning of Metal Ions to Stabilize Open Tin Sites in Beta Zeolite for Catalytic Conversion of Sugars

AbstractVia hydrothermal synthesis of Sn‐Al gels, mild dealumination and ion exchange, a bimetallic Sn‐Ni‐Beta catalyst was prepared which can convert glucose to methyl lactate (MLA) and methyl vinyl glycolate (MVG) in methanol at yields of 71.2 % and 10.2 %, respectively. Results from solid‐state magic‐angle spinning nuclear magnetic resonance, X‐ray photoelectron spectroscopy, transmission electron microscopy, spectroscopic analysis, probe‐temperature‐programmed desorption, and density functional theory calculations conclusively reveal that the openness of the Sn sites, such as by the formation of [(SiO)3−Sn−OH] entities, is governed by an adjacent metal cation such as Ni2+, Co2+, and Mn2+. This relies on the low structure‐defective pore channel, provided by the current synthesis scheme, and the specific silica hydroxyl anchor point is associated with the incorporation of Sn for additional and precise metal ion localization. The presence of metal cations significantly improved the catalytic performance of Sn‐Ni‐Beta for glucose isomerization and conversion to MLA of sugar compared with Sn‐Beta.

Rational Positioning of Metal Ions to Stabilize Open Tin Sites in Beta Zeolite for Catalytic Conversion of Sugars.

Via hydrothermal synthesis of Sn-Al gels, mild dealumination and ion exchange, a bimetallic Sn-Ni-Beta catalyst was prepared which can convert glucose to methyl lactate (MLA) and methyl vinyl glycolate (MVG) in methanol at yields of 71.2% and 10.2%, respectively. Results from solid-state MAS NMR, XPS, TEM, spectroscopic analysis, probe-TPD, and DFT calculations conclusively reveal that the openness of the Sn sites, such as by the formation of [(SiO)3-Sn-OH] entities, is governed by an adjacent metal cation such as Ni2+, Co2+, and Mn2+. This relies on the low structure-defective pore channel, provided by the current synthesis scheme, and the specific silica hydroxyl anchor point is associated with the incorporation of Sn for additional and precise metal ion localization. The presence of metal cations significantly improved the catalytic performance of Sn-Ni-Beta for glucose isomerization and conversion to MLA of sugar compared with Sn-Beta.

Cassiterite deposition induced by cooling of a single-phase magmatic fluid: Evidence from SEM-CL and fluid inclusion LA-ICP-MS analysis

Cassiterite (SnO2), the principal ore mineral of tin, is mainly formed in granite-related magmatic hydrothermal systems. The precipitation mechanism of this mineral in hydrothermal veins is still debated due to lack of direct constraints on this specific mineralization process. Here, we present a detailed reconstruction of fluid evolution history from a high-grade cassiterite-quartz vein in the Weilasituo Sn-polymetallic deposit, North China, based on combined SEM-CL imaging with fluid inclusion microthermometry, Raman and LA-ICP-MS analysis of intergrown cassiterite and gangue minerals.Formation of the cassiterite-quartz vein at Weilasituo started from early topazization and muscovite deposition along vein walls and was followed by crystallization of topaz, quartz (Q1) and cassiterite in a general sequential order. Cassiterite deposition occurred within a restricted time period before complete crystallization of topaz and quartz. Shortly after cassiterite precipitation, the vein was fractured and overprinted by later quartz generations (Q2 & Q3) and fluorite. In situ microanalysis on primary and/or pseudosecondary fluid inclusions from the different crystallization stages indicates that an acid and reduced single-phase magmatic fluid of gradually dropping temperature but very consistent salinity was responsible for vein formation. Mixing of this magmatic fluid with a biotite-plagioclase gneiss buffered, deep-cycled underground water of lower temperature and salinity occurred at the final stage, but it is not related to Sn mineralization. The physical and chemical changes of fluids bracketing cassiterite deposition demonstrate that cassiterite precipitation at Weilasituo was predominately induced by the cooling of the hydrothermal fluid by at least 50 °C, and it is accompanied by the oxidation of Sn(II)-Cl complexes with CO2 and/or As(III) species as potential oxidants. Early stage fluid-rock interaction with feldspathic host rocks and the formation of muscovite coverage on the vein walls are perhaps important for providing a fluid-buffered environment ideal for such mechanism. However, our result argues against meteoric water mixing or fluid boiling being the triggers of cassiterite deposition, and this conclusion has been further supported by cassiterite oxygen isotope analysis on the same set of samples.Additionally, the maximum base metal endowment (Pb and Zn) calculated from initial metal contents of the premineralization fluid at the Weilasituo Sn-polymetallic deposit are far less than proven reserves found in the two adjacent base metal deposits, and therefore a genetic link between these deposits is not suggested. This finding may have important implications for the ongoing exploration in the ore district.

O-bridged Fe-W dual-atom co-anchored on carbon nitride for highly efficient solar-induced peroxymonosulfate activation

Constructing dual-atom catalysts (DACs) is an appealing strategy since the synergistic interaction of adjacent active metal atoms can improve the catalytic activity while maintaining high stability. However, the rational design of DACs and the insightful understanding of the structure-performance relationship remain the central tasks. Herein, we construct a unique DAC consisting of O-bridged Fe-W heterodimer embedded in graphitic carbon nitride (Fe-W-CN), which is synthesized by pre-fixing and pyrolysis process. In Fe-W-CN, the O-coordinated Fe-W atoms are anchored in CN vacancies through nitrogen atoms with N-Fe-O-W-N configuration. The W-O site acts as a “nail” to stable the Fe atom during oxygen-containing calcination, and the final formed N-Fe-O-W-N moiety also can resist the attack of strong oxidizing radicals to achieve high stability. The density functional theory calculation indicates that the Fe atom is the main active site for peroxymonosulfate (PMS) adsorption and activation. Meanwhile, electrons generated by photoexcited CN can accelerate the recycling of Fe3+/Fe2+ for high catalytic activity. Fe-W-CN exhibits a high CBZ removal efficiency through the activation of PMS, which is 6.9 times higher than CN. This work paves the way to develop novel DACs with stable and high catalytic efficiency.

Nickel and cobalt coordination complexes: Magnetic investigations and application values on acute pancreatitis combined with abdominal infection

Two novel coordination complexes, namely, [Ni2(TPT)2(H2O)2] (1) and [Co(TPT)(H2O)2]n (2), based on the 3-(tetrazol-5-yl)-5-(pyrid-2-yl)-1,2,4-triazole ligand were produced by solvothermal synthesis. Magnetic studies showed that between adjacent metal ions, anti-ferromagnetic coupling existed in complexes 1 and 2. The complexes’ application values against catecholamine vasoactive drug-induced acute pancreatitis complicated with abdominal infection was discussed. Subsequently, the mechanism was investigated. ELISA analysis was initially used to identify the inflammatory-response levels in acute pancreatitis complicated with abdominal infection after treatment with the complex. Additionally, the C-reactive protein content of plasma was tested through the immuno-projection turbidimetric approach.

Increasing the Distance of Adjacent Palladium Atoms for Configuration Matching in Selective Hydrogenation

AbstractPrecisely tailoring the distance between adjacent metal sites to match adsorption configurations of key species for the targeted reaction pathway is a great challenge in heterogeneous catalysis. Here, we report a proof‐of‐concept study on the atomically sites‐tailored pathway in Pd‐catalyzed acetylene hydrogenation, i.e., increasing the distance of adjacent Pd atoms (dPd‐a‐Pd) for configuration matching in acetylene semi‐hydrogenation against coupling.dPd‐a‐Pdis identified as a structural descriptor for describing the competitiveness for reaction pathways, and the increaseddPd‐a‐Pdprefers the semi‐hydrogenation pathway due to simultaneously promoted C2H4desorption and the destabilized transition state of the C2H3* coupling. Spectroscopic, kinetics and electronic structure studies reveal that increasingdPd‐a‐Pdto 3.31 Å delivers superior selectivity and stability due to energy matching and appropriate hybridization of Pd 4d with In 2s and, especially, 2p orbitals.

Multilayered Alternating-Cations-Intercalation Chiral Hybrid Perovskites with High Circular Polarization Sensitivity.

Multilayered chiral hybrid perovskites are highly desired for highly-sensitive circularly polarized light (CPL) detection rooted in their efficient charge transport and strong chiroptical activity. However, designing multilayered chiral hybrid perovskites remains a huge challenge. Here, through pairing achiral ethylamine (EA)-chiral arylamine in the interlayer space, multilayered chiral alternating cations intercalation-type (ACI) hybrid perovskites (R-/S-PPA) EA2 Pb2 Br7 (PPA = 1-phenylpropylamine) are successfully obtained. Significantly, perovskitizer EA extends the thickness of the quantum well and alternating space cation EA greatly alleviates in-plane tilting distortions of adjacent metal halide octahedra, providing fast channels for in-plane carrier transport. Consequently, single-crystal photodetectors of (R-/S-PPA) EA2 Pb2 Br7 exhibit high circular polarization sensitivity with a large anisotropy factor of 0.3, which falls around the highest value among the layered hybrid perovskites. In addition, a fast responding rate (τr )of 308 µs and a high CPL-detectivity of 8× 1012 Jones are also presented. This work opens up a new perspective to design multilayered chiral hybrid perovskites for high-sensitive CPL detection.