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We present the saturated absorption spectroscopy of the 30012 ← 00001 band of 12C16O2
by a comb-locked cavity ring-down spectrometer near 1.57 μm. Positions of 37 lines with
rotational quantum numbers up to 68 were determined with an accuracy of a few kHz.
Comparisons of the ro-vibrational energy levels determined in this work with the Doppler-
limited experimental values from literature and those from the CDSD2019 databank are
given
There is an ideal desire to develop the high-performance anodes materials for Li-ion batteries (LIBs), which requires not only high stability and reversibility, but also rapid charging/discharging rate. In this work, we built a blue phosphorene-graphene (BlueP-G) intralayer heterostructure by connecting BlueP and graphene monolayers at zigzag edges with covalent bonds. Based on the density functional theory simulation, the electronic structure of the heterostructure, Li adsorption and Li diffusion on heterostructure were systematically investigated. Comparing to the pristine BlueP, the existence of graphene layer increases the overall conductivity of BlueP-G intralayer heterostructure. The significantly enhanced adsorption energy indicates the Li deposition on anode surface is energetically favored. The fast diffusion of Li with energy barrier as low as 0.02‒0.09 eV indicates the growth of Li dendrite could be suppressed and the stability and reversibility of the battery will be increased. With a combination of increased conductivity of electronic charge, excellent Li adsorption and Li mobility on surface, BlueP-G intralayer heterostructure with zigzag interface is quite promising in the application of anode material for Li-ion batteries.
Controlling the local electronic structure of active ingredients to improve the adsorption-desorption characteristics of oxygen-containing intermediates over the electrochemical liquid-solid interfaces is a critical challenge in the field of oxygen reduction reaction (ORR) catalysis. Here, we offer a simple approach for modulating the electronic states of metal nanocrystals by bimetal co-doping into carbon-nitrogen substrate, allowing us to modulate the electronic structure of catalytic active centers. To test our strategy, we designed a typical bimetallic nanoparticle catalyst (Fe-Co NP/NC) to flexibly alter the reaction kinetics of ORR. Our results from XAS (synchrotron X-ray absorption spectroscopy) and XPS (X-ray photoelectron spectroscopy) showed that the co-doping of iron and cobalt could optimize the intrinsic charge distribution of Fe-Co NP/NC catalyst, promoting the oxygen reduction kinetics and ultimately achieving remarkable ORR activity. Consequently, the carefully designed Fe-Co NP/NC exhibits an ultra-high kinetic current density at the operating voltage (71.94 mA cm-2 at 0.80 V), and the half-wave potential achieves 0.915 V, which is obviously better than that of the corresponding controls. Our findings provide a unique perspective for optimizing the electronic structure of active centers to achieve higher ORR catalytic activity and faster kinetics.
The search for stable and efficient single-atom catalysts (SACs) for the electrocatalytic nitrogen reduction reaction (eNRR) has garnered significant theoretical interest. In this study, we evaluate the eNRR performance of eighteen two-dimensional 1T-MoSe2-supported transition metal single-atom catalysts (TM@1T-MoSe2, TM =V~Ni, Nb~Pd, Ta~Pt) using density functional theory (DFT) calculations. We assess the stability of each TM@1T-MoSe2, as well as the limiting potential of eNRR and the ammonia selectivity on each stable TM@1T-MoSe2. Our results show that W@1T-MoSe2 is the most promising SAC for eNRR, with a limiting potential of -0.23 V via the distal pathway starting from three co-adsorbed nitrogen molecules. Furthermore, the multi-adsorption of N2 on W@1T-MoSe2 effectively suppress the hydrogen evolution reaction (HER), thus enhancing the selectivity of the eNRR. This research provides a promising avenue for the development of a new class of 1T-MoSe2-based single-atom catalysts for electrocatalytic ammonia synthesis.
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As a new generation of semiconductor materials, two-dimensional (2D) black phosphorene (BlackP) has broad application prospects because of its tunable band gap and high carrier mobility. However, BlackP cannot be directly prepared at a large scale at present, which limits its further research and application. Molecular beam epitaxy (MBE) is a widely used way to grow single crystal films with higher epitaxial quality, which is promising for preparing BlackP. Herein, four potential substrates ZnO(110), GaN(110), BP (110) and SiC(110) were screened, and the growth of BlackP on these substrates was studied based on first principles. Our study shows that the structure of black phosphorus monolayer on ZnO(110) is stable and P diffusion on this surface has desirable properties for BlackP growth. This study provides useful guides to efficiently prepare BlackP and also for the growth of other two-dimensional materials.
With the blooming development of electronic technology, the use of electron conductive gel or ionic conductive gel in preparing flexible electronic devices is drawing more and more attention. Deep eutectic solvents are excellent substitutes for ionic liquids because of their good biocompatibility, low cost, and easy preparation, except for good conductivity. In this paper, we synthesized a reactive quaternary ammonium monomer (3-acrylamidopropyl)octadecyldimethyl ammonium bromide with a hydrophobic chain of 18 carbons via the quaternization of 1-bromooctadecane and N-dimethylaminopropyl acrylamide at first, then we mixed quaternary ammonium with choline chloride (ChCl), acrylic acid (AA) and glycerol (Gly) to obtain a hydrophobic deep eutectic solvent (DES), and initialized polymerization in UV light of 365 nm to obtain the ionic conductive eutectogel based on polyacrylamide copolymer with long hydrophobic chain. The obtained eutectogel exibits good stretchability (1200%), Young's modulus (0.185 MPa), toughness (4.2 MJ/m3), conductivity (0.315 S/m). The eutectogel also shows desireable moisture resistance with a maximum water absorption of 11.7 wt% after one week at 25 ℃ and 60% humidity, while the water absorption of eutectogel without hydrophobic long chains is 23.4 wt%. The introduction of long-chain hydrophobic groups not only improved the mechanical strength of the gels, but also significantly improved moisture resistance of the eutectogel. This paper provides a simpler and more effective method for the preparation of ionic conductive eutectogels, which can further provide a reference for the applications of ionic conductive eutectogels in the field of flexible electronic devices.
Atomically dispersed copper and nitrogen-doped carbon (Cu-N-C) materials are promising electro-driven CO2 reduction (CO2RR) catalysts. A comprehensive mechanistic understanding of Cu-N-C towards systematic improvement, however, is hampered by the complexity of electrode–electrolyte interface around Cu. Here, we adopted an electric double layer model to investigate the impact of alkali metal cations on the two-electron CO2RR catalyzed by Cu-N4-C under applied potential. The grand canonical density functional theory calculations show that, (1) at U=-1.2 V vs SHE, hydrated Na+ ions near the surface facilitate formation of bent CO2-bonding with Cu; (2) with an increasingly negative potential, the electrosorption of CO2 (Cu + CO2 + e- → Cu-CO2-) instead of the formation of COOH, becomes the presumable rate determining step for Na+-aided COformation. Further, a possible Cu(I) may be vital for the adsorption of anionic COOH. Our study demonstrates the crucial role of alkali metal ion in the early stage of CO2RR on Cu-N4-C and the importance of explicit consideration of the applied potential in simulation for a better understanding on the reaction mechanism.
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The characterization of the structures of molecular clusters, which serve as building blocks for bulk substances, provides crucial insight into the interactions between constituent units. Chirped-pulse Fourier transform microwave (CP-FTMW) spectroscopy, combined with state-of-the-art quantum chemical calculations, is a powerful tool for characterizing the structures of molecular clusters, as the rotational spectra are directly related to the mass distribution of a molecule or cluster. However, determining the structures of large or complex clusters from experimental rotational spectra remains challenging due to their structural flexibility. DFT calculations for searching their stable structures could be significantly time-consuming and method-dependent. To address these challenges, we have developed an approach that relies on the experimental rotational constants to search for potential molecular structures without quantum chemical optimization. Our approach involves creating an initial set of conformers through either a semi-empirical sampling program or the Quasi-Monte Carlo method. Afterward, the Trust Region Reflective (TRR) algorithm is utilized for structural fitting. This procedure enables us to quickly generate potential conformers and gain access to precise structural information. We applied our fitting program to water hexamer and benzaldehyde-water clusters, and the resulting topological structures aligned extremely well with the experimental results.
It was experimentally found that the gold-catalyzed reaction between <i>o</i>-alkynylphenols with aryldiazonium salts can lead to different products under thermo- and photo-catalytic conditions; however, the mechanism is elusive. Herein we have employed both MS-CASPT2 and DFT approaches to study the catalytic mechanisms of the corresponding light- and thermal-driven reactions. The results show that both the thermo- and photo-catalytic reactions share some same elementary steps from the Au(I) catalyst and <i>o</i>-alkynylphenol, both of which generate a vinyl Au(I) intermediate with the aid of HCO<sub>3</sub><sup>-</sup>. In these steps, the formation of a structurally distorted complex of the Au(I) catalyst and <i>o</i>-alkynylphenol has a free-energy barrier of 14.8 kcal⋅mol<sup>-1</sup> in that the C-C triple bond of <i>o</i>-alkynylphenol is seriously activated. Importantly, the thermo- and photo-catalytic reactions start to diverge from the complex formed between the generated vinyl Au(I) intermediate and the aryldiazonium salt. In the dark condition, the reaction proceeds to generate the final thermal product after overcoming a free-energy barrier of 15.7 kcal⋅mol<sup>-1</sup>, in which the terminal N atom of the aryldiazonium salt is bonded directly to the C atom of the Au(I) species. In the photoirradiation condition, the complex is first excited to its electronically excited singlet state, which then decays to the T<sub>1</sub> state with an efficient intersystem crossing process of 9.8×10<sup>9</sup> s<sup>-1</sup>. In the T<sub>1 </sub>state, the denitrogen process is in complete easily after overcoming a free-energy barrier of 7.8 kcal⋅mol<sup>-1</sup> resulting into an aryl radical interacted with the Au atom of the vinyl Au(I) species, which is followed by another intersystem crossing process from T<sub>1</sub> to S<sub>0</sub>. In the S<sub>0</sub> state, the final photocatalytic product is formed. The present work sheds important mechanistic details on understanding both thermo- and photo-catalytic reactions of Au(I) catalysts and aryldiazonium salts and most importantly, it is found that nonradiative transitions play an essential role in regulating photocatalytic reactions.
NiOx as a hole transport material for inverted perovskite solar cells (iPSCs) has received great attention owing to its high transparency, low fabrication temperature, and superior stability. However, the mismatched energy levels and possible redox reactions at the NiOx/perovskite interface severely limit the performance of NiOx-based iPSCs. Herein, we introduce a p-type self-assembled monolayer (SAM) between NiOx and perovskite layers to modify the interface and block the undesirable redox reaction between perovskite and NiOx. The SAM molecules all contain phosphoric acid function groups, which can be anchored onto the NiOx surface and passivate the surface defect. Moreover, the introduction of SAMs can regulate the energy level structure of NiOx, reduce the interfacial band energy offset, and hence promote the hole transport from perovskite to NiOx layer. Consequently, the device performance is significantly enhanced in terms of both power conversion efficiency (PCE) and stability.
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The study of m-Xylene photoionization and dissociation photoionization using synchrotron vacuum ultraviolet (VUV) light and supersonic expanding molecular beam reflection time-of-flight mass spectrometer system. Photoionization efficiency curves (PIEs) of molecule ion C8H10+ and fragment ions C8H9+ and C7H7+ were observed, and the ionization energy (IE) and the appearance energies (AEs) of the fragment ions C8H10+, C8H9+ and C7H7+ are obtained to be 8.59eV, 11.74eV and 11.89eV, respectively. Optimized structures of transitional states, intermediates, and product ions were characterized at the B3LYP/6-311++ G (d, p) basis sets, and the energies were calculated using the G3 method. Based on the results, two major dissociative photoionization channels, C7H7++CH3 and C8H9++H have been calculated at the B3LYP/6-311++ G (d, p) level. With the combination of theoretical and experimental results, the dissociative photoionization pathways of m-Xylene are proposed. The predominant m-Xylene cleavage mechanism is hydrogen migration.
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We calculate the interaction strength of the van der Waals force between two Rydberg atoms by applying the applications of quantum information processing using for Rydberg blockade. The alkali metals (Cs and K) in states of principal quantum number n were used to calculate the interaction strength. We use some possible angular momentum channels involving s, p, and d states for measuring interaction strength. The obtained results were then generalized for all angular momentum channels which mostly have small interactions and therefore a poor candidate for blockade experiments. The interaction strength in the atoms of Cs and K dipole matrix elements was calculated first and then relevant energy levels were determined by using the quantum defects theory. The radial wave function was calculated numerically with the integration of the radial Schrödinger equation. Also, the interaction coefficients of van der Waals for various channels were calculated here.
