Chemical Charge Research Articles

Interplay between protonation and Jahn-Teller effects in a manganese vanadium cubane water oxidation catalyst.

Understanding the protonation behavior of metal-oxo water oxidation catalysts is essential to improve catalyst efficiency and long-term performance, as well as to tune their properties for specific applications. In this work, we explore the basicity and protonation effects of the highly active water oxidation catalyst [(Mn4O4) (V4O13) (OAc)3]3- using density functional theory. We computed the relative free energies of protonation in a systematic fashion for all symmetry-inequivalent O atoms, where the presence of multiple oxidation states from Mn4IV to Mn4III and a rich Jahn-Teller isomerism adds a significant amount of complexity. For high oxidation states, the compound behaves like some other polyoxometalates, showing protonation preferably at the terminal and μ2-bridging O atoms of the vanadate cap. However, upon reduction, eventually, the protonation preference switches to the cubane O atoms, mostly driven by a strong increase in basicity for O atoms located along the Jahn-Teller axes. Our work further evidences that protonation can potentially lead to several chemical transformations, like disproportionation and charge transfer to vanadium, dissociation of ligands, or the opening of the cubane structure. Our simulated UV/Vis absorption spectra additionally provide valuable insights about how the protonation of the catalyst could be tracked experimentally. Overall, our analysis highlights the complexity involved in the protonation of heterometallic polyoxometalate clusters.

Adsorption of toxic and harmful gas NO2 and SO2 on TM (Fe, Co and Ni) modified ZrSe2 monolayer: A DFT study

Based on density functional theory (DFT), the adsorption properties of ZrSe2 monolayer modified by transition metals (Fe, Co and Ni) to NO2 and SO2 of two harmful gases are predicted in this paper. The calculation results indicate that ZrSe2 monolayer modified by metal atom loading is more stable than that doped by metal atom. Therefore, the adsorption behavior of ZrSe2 modified by metal atom loading on two harmful gases is studied. The results demonstrate that the adsorption energy of ZrSe2 monolayer loaded with metal atoms can be significantly improved the adsorption energy of the system, and the chemical bond and charge transfer between metal atoms and gas molecules are generated, indicating a strong interaction between metal atoms and gas. Besides, NO2 gas adsorption on a substrate loaded with metal atoms is superior than that of SO2 gas. The Ni-ZrSe2 system is suitable for NO2 gas sensor, Fe-ZrSe2 system and Co-ZrSe2 system are suitable for SO2 gas sensor according to the comparison of work function and recovery time of different gas configurations. Taken together, this study will provide new directions and theoretical foundations for possible applications of (Fe, Co and Ni)-ZrSe2 monolayers in sensing and processing NO2 and SO2 gases.

Fabrication and characterization of CuO–SiO2/PVA polymer nanocomposite for effective wastewater treatment and prospective biological applications

ABSTRACT The quality of water significantly affects the health and walefare of all orginisms, highlighting the importance to develop low-cost and efficient wastewater treatment methods. Herein, we report the fabrication, characterization, and utilization of a polymer-based ternary nanocomposite (CuO–SiO2/PVA) for the removal of Nile Blue (NB) and Methylene Blue (MB) contaminants from wastewater, along with exploring its potential biological activities. We have successfully employed the cost-effective sol–gel and in-situ polymerization approaches to fabricate the CuO–SiO2/PVA based ternary composite, utilizing Cu(NO3)2·3H2O:Glycerol:TEOS:PVA in a ratio of 8:2:3:4. The desired fabrication of nanocomposite was confirmed through UV-Visible spectroscopy, SEM (scanning electron microscope), TEM (transmission electron microscope), EDX (energy dispersive X-ray diffraction), FTIR (Fourier transform infrared), DSC (differential scanning calorimetry), and TGA (thermogravimetric analysis). In addition to its biological potentialthe performance of the nanocomposite in catalytic / photocatalytic removal of NB and MB dyes is investigated and compared. The higher photodegradation performance of the composite for NB (85%) dye than for MB (76%) dye indicates that variables such as chemical structure, charge, molecular mass, and pH sensitivity of the dyes can influence the catalyst's removal potential. This composite is considered to have a higher capability for removing pollutants and microorganisms from wastewater.

Taylor dispersion analysis using capacitively coupled contactless conductivity detector

Taylor dispersion analysis (TDA) is a simple and absolute method to determine the hydrodynamic radius of solutes that respond to UV or fluorescence detections. To broaden the application range of TDA, it is necessary to develop new detection modes. This study aims to study capacitively coupled contactless conductivity detector (C4D) for the analysis of charged macromolecules. The detection sensitivities and hydrodynamic radii were compared for a C4D detector and a UV detector on positively or negatively charged polymers responding both to UV and C4D (poly-L-lysine and poly(acrylamide-co-2-acrylamido-1-methyl-propanesulfonate). The influence of the composition of the background electrolyte on the detection sensitivity has been studied and optimized for C4D detection. The influence of the molar mass and of the polymer chemical charge density on the C4D and UV sensitivities of detection have been investigated based on well-characterized copolymers samples of different molar masses and charge densities. The advantages and disadvantages compared to UV detection, as well as the range of applicability of C4D detection in TDA were identified. C4D detection can be an alternative method for sizing charged polymers of reasonable molar mass (typically below 105 g mol−1) that do not absorb in UV. A decline in the sensitivity of detection in C4D was observed for higher molar masses.

Investigation of the mechanism of solvothermal extraction of direct coal liquefaction residue by macromolecular models

Direct coal liquefaction residue (DCLR) is an industrial by-product from the direct coal liquefaction process. It has the unique characteristics of high carbon, high sulfur and high ash content, strong cohesiveness and low softening point, which makes DLCR a potential raw material. However, direct discharge of untreated DCLR can cause severe damage to environment and human body. Thus it is of great importance to utilize DCLR properly. In this study, solvothermal extraction of direct coal liquefaction residue (DCLR)was treated with N-methyl-2-pyrrolidone (NMP) and 1-methyl naphthalene (1-MN). In addition, molecular models of DCLR and two hypercoals (HPC: NMP-HPC, MN-HPC) were built to clarify the extraction mechanism, aiming to provide a technically feasible route to utilize DCLR and investigate the adaptation between extractant and raw materials. The structural parameters were obtained by means of industrial and elemental analysis, 13C NMR, XPS and FTIR. Subsequently, macromolecular structure models were constructed, with simulated molecular formulas C153H108N2O10S, C206H168N6O7 and C278H202N2O13S, respectively. After modifying the macromolecular models by Materials Studio for geometric optimization, annealing dynamics calculation, density simulation and analysis of chemical bonds and charge layout, these models reflected the macromolecular structural characteristics precisely. On the other hand, DCLR model underwent significant changes in functional groups, branched chain length and quantity pre and post solvothermal extraction, indicating that the thermal extraction process was mainly affected by swelling behavior and pyrolysis. Meanwhile the principles of the two extractants were also different.1-MN extraction was a heat-induced relaxation, while NMP extraction was heat & solvent-induced relaxation process. This study will be helpful in expanding the utilization of DCLR and understanding of mechanism of solvothermal extraction on the macromolecular level based on modeling.

Quantum chemical explanation and APT atomic charge index of substituent orienting effect proposed by DFT calculation and MO Theory

AbstractIn organic chemistry textbooks, the electron resonance states are used to explain the orienting effect of benzene substituent. However, these resonance states do not exist in the C6H5‐S + E+ electrophilic addition, so the resonance state discussions actually are meaningless. The density functional theory (DFT) calculation shows that the C6H5‐S + E+ addition follows the transition state theory and needs to overcome a barrier. Benzene molecule C6H6 has two degenerate highest occupied molecular orbitals (HOMOs), but after becoming substituted benzenes, the two HOMOs split to HOMO and HOMO‐1 with different orbital energies and electron distributions. It makes the addition barrier on two or three benzene ring carbons is low, and the addition rate is fast, but the barrier of other carbons is high, and the rate is slow. Therefore, substituent splits the two degenerate HOMOs of benzene molecule, which is the origin of substituent orienting effect. For the substituted benzenes with halogen group ‐X and electron‐releasing group, their HOMO images alone can determine that the two types of substituents are the ortho‐ and para‐orienting groups, but for the substituted benzenes with electron‐withdrawing group, their HOMO alone cannot determine whether the substituent is a meta‐orienting group. The study found that atomic polar tensor (APT) charges are a good judgment index of substituent orienting effect because based on its physic‐chemical model, the charges represent the number of active electrons on the benzene ring carbons. The DFT calculation gives the APT charges of 19 mono‐substituted and 12 di‐substituted benzenes and some aromatic molecules. The APT charges can all correctly determine their orienting effects, showing that APT atomic charge from quantum theoretical calculation is a good substituent orienting index.

Aerobically Autoxidized Self-Charge Concept Derived from Synergistic Pyrrolic Nitrogen and Catechol Configurations in N, O Co-Doped Carbon Cathode Material.

Aerobically autoxidized self-charging concept has drawn significant attraction due to its promising chemical charge features without external power supply. Particularly, heteroatom-doped carbon materials with abundant oxidizable sites and good conductivity are expected to be ideal cathode materials. However, there is no well-defined aerobically autoxidized self-charging concept based on heteroatom-doped carbon materials, significantly hindering the design of related carbon cathodes. An aerobically autoxidized self-chargeable concept derived from synergistic effect of pyrrolic nitrogen and catechol configuration in carbon cathode using model single pyrrolic nitrogen and oxygen (N-5, O) co-doped carbon and O-enriched carbon is proposed. First, self-charging of N-5, O co-doped carbon cathode can be achieved by aerobic oxidation of pyrrolic nitrogen and catechol to oxidized pyrrolic nitrogen and ortho-quinone configurations, respectively. Second, introducing a single pyrrolic nitrogen configuration enhanced acidic wettability of N-5, O co-doped carbon facilitating air self-charge/galvanic discharge involving proton removal/introduction. Third, synergistic effect of pyrrolic nitrogen and hydroxyl species with the strong electron-donating ability to conjugated carbon-based backbone endows N-5, O co-doped carbon with a higher highest occupied molecular orbital (HOMO) energy level more susceptible to oxidation charging. The assembled Cu/Carbon batteries can drive a timer after every air-charging run. This promising aerobically autoxidized self-charging concept can inspire exploring high-efficiency self-charging devices.

Single-Cell Caspase-3 Measurement Using a Biomimetic Nanochannel.

Direct single-cell caspase-3 (Casp-3) analysis has remained challenging. A study of single-cell Casp-3 could contribute to revealing the fundamental pathogenic mechanisms in Casp-3-associated diseases. Here, a biomimetic nanochannel capable of single-cell sampling and ionic detection of intracellular Casp-3 is devised, which is established upon the installment of target-specific organic molecules (luc-DEVD) within the orifice of a glass nanopipette. The specific cleavage of luc-DEVD by Casp-3 could induce changes of inner-surface chemical groups and charge properties, thus altering the ionic response of the biomimetic nanochannel for direct Casp-3 detection. The practical applicability of this biomimetic nanochannel is confirmed by probing intracellular Casp-3 fluctuation upon drug stimulation and quantifying the Casp-3 evolution during induced apoptosis. This work realizes ionic single-cell Casp-3 analysis and provides a different perspective for single-cell protein analysis.

Sodium Carbonate Pulping of Wheat Straw—An Alternative Fiber Source for Various Paper Applications

European paper mills are currently facing the question of whether recovered paper, their main raw material, will be available in sufficient quantities and an acceptable quality in the future. An alternative to recovered paper or wood fiber is the use of agricultural residues such as wheat straw. Sodium carbonate-based straw pulping processes have the advantage of not requiring recausticizing for chemical recovery, which reduces investment and operating costs. With the addition of oxygen, delignification can be significantly improved to provide pulps suitable for bleaching. This study compares the pulping of wheat straw using sodium carbonate, sodium carbonate + oxygen, and sodium carbonate + sodium hydroxide + oxygen. Pulping parameters such as temperature, retention time, and chemical charge were varied, and their influence on pulp properties was studied. The use of sodium carbonate alone produced pulps with high yields of up to 72% and comparably high burst and compressive strength. The addition of oxygen and small amounts of sodium hydroxide produced pulps with a high initial brightness of 42 %ISO and a low kappa number (18), still at high pulp yields of 62%. These pulps were two-stage bleached to achieve brightness levels of up to 73 %ISO.

THE EFFECT OF THE FLUORINE CONCENTRATION IN A PLASMA-FORMING GAS MIXTURE ON THE CHEMICAL COMPOSITION, SURFACE CHARGE, AND RELIEF PARAMETERS OF FLUOROCARBON COATINGS ON PET

In this work, the main factors influencing the appearance of the antiadhesive properties on the surface of polyethylene terephthalate (PET) with a fluorocarbon film were considered. The chemical composition, surface charge, and surface relief of antimicrobial fluorocarbon films deposited on PET were studied. The fluorocarbon films were formed by ion-plasma technology at reduced pressure using a two-component gas mixture consisting of tetrafluoromethane and cyclohexane.

Enhancing the adsorption-photocatalytic efficiency of BiOBr for Congo red degradation by tuning the surface charge and bandgap via an Y3+-I- co-doping strategy.

Metal-ion doping and halogen substitution have been largely applied to tune the bandgap of bismuth oxybromide (BiOBr) to upgrade its photodegradation capacity. In this work, the adsorption capacity and photocatalytic behavior of solvothermally synthesized BiOBr photocatalysts can be optimized via the synergistic effect of Y3+- and I--doping. After an adsorption reaction in the dark and exposure for another 80 min to visible light, pure BiOBr can remove 46.5% of Congo red (CR) from water with an initial CR concentration of 50 mg L-1. Meanwhile, Bi0.8Y0.20OBr0.97I0.03, the co-doped catalyst, displays total degradation rates exceeding 98% and 92% with CR dosages of 50 and 100 mg L-1, respectively, demonstrating a doubled degradation capacity. With the co-doping solution, the negative charges on the catalysts reduce, more oxygen vacancies are generated, the bandgap remarkably narrows, and the photoabsorption range broadens for derivation of photoinduced electron-hole pairs. The mechanism for optimized photodegradation behavior and dramatically increased adsorption capacity are discussed based on analyses of the structural evolution, surface properties including the chemical state and surface charge, electrochemical performance and the yield/type of photogenerated species. Density functional theory (DFT) simulations were conducted to investigate the structural state, density of states (DOS) and electrostatic potential.

Co(II)-Cu(II) mixed-oxide catalysts for single-step synthesis of 2,4,5-triaryl-1H-imidazole derivatives under microwave irradiation.

In this study, a catalyst composite of Co-Cu was prepared from chloride-containing precursor of Co(II) and Cu(II) metals using the milky latex of the Euphorbia neriifolia plant following green principles of synthesis. The catalyst composite was characterized using XRD, EDAX, SEM, HR-TEM, FTIR, XPS and TOF-MS. The crystallinity of the mixed-oxide composite with a distorted octahedral nature was confirmed from analysis. Chemical charge analysis of the Co-Cu mixed phase based on XPS revealed Co2+ and Cu2+ oxidation states. This material was used for synthesizing 2,4,5-triaryl-1H-imidazole (TIMDZOL) derivatives. Analysis of reaction conditions revealed that EtOH : PEG at 8 : 2 ratio under microwave conditions showed better yields with less time and better reusability of the Co-Cu catalyst.

The ions storage mechanism of capacitive-faradic coupling effect for pseudo-intercalation electrode MnO2

As one of the most promising faradic intercalation electrode materials, manganese dioxide (MnO2) has broad prospects in capacitive deionization for heavy metal removal. However, there are differences in capacitive deionization kinetics of MnO2 with different crystal structures, and the capacitive and faradic multi-process coupling mechanism are still unclear, which limits the optimization and development of these pseudo-intercalation electrodes. Here, we propose the potential ions storage routes involved into the capacitive and faradic coupling behavior and quantitatively analyze the evolution laws of heavy metal Cd2+ with respect to different crystal-structured MnO2 (α, β and δ). Mediated by the released electron from the cathode, Mn4+/Mn3+ faraday reaction on the MnO2 generates a large amount of surface faradic chemical charge (Mn-OH/Mn-O-), thereby driving the surface faradic storage of Cd2+ ions (28 %∼47 %). This finding breaks the traditional recognition that the pseudocapacitive deionization of MnO2 is dominated only tunnel pseudo-intercalation (14 ∼ 54 % in this study) and surface capacitive progress (12 ∼ 34 % in this study). Additionally, the fixed chemical-charge-controlled storage derived from crystal surface defect also contributed 4 ∼ 8 % to the total. Mn-O bond length is key to determine the tunnel intercalation capacity and the electron transfer ability along Mn4+-O-Mn3+ path to generates Mn4+/Mn3+ faradic charge, thus the surface faradic chemical-charge-controlled storage (β > α > δ) and pseudo-intercalation storage (δ > α > β) showed a potential mutual restriction effect. In this study, the electrochemical behavior of heavy metal ions and charge transfer mechanism at the interface of the MnO2 electrode were effectively clarified by combining the theoretical model and electrochemical analysis, which provided a new idea for expanding the understanding of the multiple ion storage processes coupling mechanism of intercalation materials and forming the regulation strategy for efficient capacitive coupled with faradic electrochemical deionization electrode materials.

Solvents performance, experimental spectral energies interactions, excitations energies, topological and electrophilic molecular interaction studies on 4?-(bromomethyl)-[1,1?-biphenyl]-2-carbonitrile- antiphobic disorder agent

An organic chemical compound, 4′-(bromomethyl)-[1,1′-biphenyl]-2-carbonitrile, was synthesized and characterized experimentally and computationally. The geometry of the molecule was attained utilizing computational approaches with B3LYP/6–311++ G (d, p) compared with experimental results. To identify modes of vibration and foretell their functional groups, these compounds were described using FTIR and FT-Raman spectroscopic techniques. The included electronic transitions in the molecule were depicted by comparing the anticipated UV–vis spectrum with the experimental spectrum. The calculated and measured spectra are actually rather similar. On the other hand, research has been done on evaluating FMO, global reactivity of chemical descriptions, aromaticity, and natural charge. MEP (Molecular Electrostatic Potential), ELF (Electron Localized Function), and LOL (Local Orbital Localization) maps were carried out. While biological score prediction were used as evidence for the biological attributes. This substance also complies with Lipinski's rule of five, which means that, in theoretical, ingesting a pill of such drugs shouldn't be troublesome. A protein was eventually bonded using the molecular docking technique.

Defect Strategy in Solid-State Lithium Batteries.

Solid-state lithium batteries (SSLBs) have great development prospects in high-security new energy fields, but face major challenges such as poor charge transfer kinetics, high interface impedance, and unsatisfactory cycle stability. Defect engineering is an effective method to regulate the composition and structure of electrodes and electrolytes, which plays a crucial role in dominating physical and electrochemical performance. It is necessary to summarize the recent advances regarding defect engineering in SSLBs and analyze the mechanism, thus inspiring future work. This review systematically summarizes the role of defects in providing storage sites/active sites, promoting ion diffusion and charge transport of electrodes, and improving structural stability and ionic conductivity of solid-state electrolytes. The defects greatly affect the electronic structure, chemical bond strength and charge transport process of the electrodes and solid-state electrolytes to determine their electrochemical performance and stability. Then, this review presents common defect fabrication methods and the specific role mechanism of defects in electrodes and solid-state electrolytes. At last, challenges and perspectives of defect strategies in high-performance SSLBs are proposed to guide future research.

A High-Resolution Spatial Distribution-Based Integration Machine Learning Algorithm for Urban Fire Risk Assessment: A Case Study in Chengdu, China

The development and functional perfection of urban areas have led to increasingly severe fire risks in recent decades. Previous urban fire risk assessment methods relied on subjective judgment, rough data collection, simple linear statistical methods, etc. These drawbacks can lead to low robustness of evaluation and inadequate generalization ability. To resolve these problems, this paper selects the indicator and regression models based on the high-resolution data of the spatial distribution characteristics of Longquanyi distinct in Chengdu, China. and proposes an integrated machine learning algorithm for fire risk assessment. Firstly, the kernel density analysis is used to map the fourteen urban characteristics related to fire risks. The contributions of these indicators (characteristics) to fire risk and its corresponding index are determined by Random Forest (RF), Gradient Boosting Decision Tree (GBDT), and eXtreme Gradient Boosting (XGBoost). Then, the spatial correlation of fire risks is determined through Moran’s I, and the spatial distribution pattern of indicator weights is clarified through the raster coefficient space analysis. Finally, with these selected indicators, we test the regression performance with a backpropagation neural network (BPNN) algorithm and a geographically weighted regression (GWR) model. The results indicate that numerical variables are more suitable than dummy variables for estimating micro-scale fire risks. The main factors with a high contribution are all numerical variables, including roads, gas pipelines, GDP, hazardous chemical enterprises, petrol and charging stations, cultural heritage protection units, assembly occupancies, and high-rise buildings. The machine learning algorithm integrating RF and BPNN shows the best performance (R2 = 0.97), followed by the RF-GWR integrated algorithm (R2 = 0.87). Compared with previous methods, this algorithm reduces the subjectivity of the traditional assessment models and shows the ability to automatically obtain the key indicators of urban fire risks. Hence, this new approach provides us with a more robust tool for assessing the future fire safety level in urban areas.

Photocatalytic degradation of multiple-organic-pollutant under visible light by graphene oxide modified composite: degradation pathway, DFT calculation and mechanism

Wastewater containing antibiotics, organic dyes, and waterborne bacteria is a severe threat to human health and the environment. Amoxicillin has a slow metabolism rate in humans. Methylene blue is mutagenic and carcinogenic. In addition, Salmonella causes serious diarrhea. In this study, an effective 2D/2D photocatalyst with excellent elimination of these pollutants was fabricated by combining graphene oxide (GO), Bi2WO6, BiPO4 and Ag species. GO was applied at varying loading contents (0.8, 1.6, 2.4, 3.2 wt%) to improve the properties of the photocatalyst toward the removal of representative pollutants. The chemical structures, morphology, light absorption and charge mobility were investigated by different GO loading samples. The results indicated that when the wt% of GO was 2.4%, the photocatalyst showed excellent photocatalytic properties and removal rates for typical pollutants. Amoxicillin and methylene blue were mineralized into CO2, H2O, and small molecules, while Salmonella was disinfected with excellent photocatalytic efficiency. Furthermore, the possible photodecomposition pathways of amoxicillin and methylene blue were proposed by DFT calculations and intermediates identified by LCMS. The mechanism of the photocatalytic process was investigated by radical trapping experiments, ESR spectroscopy, and Motty-Schottky plots. The free radicals could be produced constantly during the photocatalytic process, leading to mineralization of amoxicillin and methylene blue, and disinfection of Salmonella. In this work, a new perspective on GO modified Bi2WO6 with different loading contents and the degradation pathways of antibiotics and dyes was proposed.

Theoretical study of interaction between temozolomide anticancer drug and hydroxyethyl carboxymethyl cellulose nanocarriers for targeted drug delivery by DFT quantum mechanical calculation

In this article for the first time the quantum calculations of 3-methyl-4-oxoimidazo[5,1-d][1,2,3,5]tetrazine-8-carboxamide (Temozolomide) in HCM-Cellulose Substrate are evaluated using the B3LYP/6-31G level of theory. The non-bonded interaction effects of the molecule Temozolomide, HCM-Cellulose on the electronic properties, chemical shift tensors and natural charge have also been detected. Natural bond orbital analysis (NBO) suggests that Temozolomide as an electron donor and HCM-Cellulose acted as an electron acceptor in the Temozolomide/HCM-Cellulose complex. The electronic spectra of the Temozolomide drug and Temozolomide/HCM-Cellulose complex in were calculated by Time-Dependent Density Functional Theory (TD-DFT) for the investigation of the adsorption effect of the Temozolomide drug over HCM-Cellulose on maximum wavelength. As a result, the feasibility of using HCM-Cellulose to deliver Temozolomide to diseased cells has been established.

Computational Study on Piperazine‐1,4‐Diium Acetate Using Dft Investigations: Structural Aspects, Topological and Nonlinear Optical Properties

AbstractThe work aims to investigate the nonlinear optical (NLO) activity of piperazine‐1,4‐diium acetate (PAA) molecule utilizing computational techniques. The computational calculations are performed using density functional theory (DFT) to explore the vibrational modes, electronic and NLO properties of PAA by comparing them with piperazine and acetic acid molecules. The natural bond orbital analysis is performed to identify hydrogen bonding and charge transfer interaction. A vibrational analysis is carried out and the assignment of fundamental modes is done using the vibrational energy distribution analysis (VEDA) program. Molecular electrostatic potential, frontier molecular orbital, electron localization function, localized orbital locator and Fukui analysis are carried out to identify chemical reactivity and charge transfer interaction. The UV–visible analysis is performed to obtain the electronic absorption spectrum. The hole–electron analysis is performed for the first five excitations to identify the type of excitation. The atoms in molecules, reduced density gradient and independent gradient model are performed to identify the hydrogen bonding, steric and van der Waals interactions. Hirshfeld analysis is performed to explore the intermolecular interactions within the PAA molecule. The NLO calculation is performed to evaluate the NLO parameters. The obtained results show that the PAA molecule is suitable for NLO applications.

Activating dynamic atomic-configuration for single-site electrocatalyst in electrochemical CO2 reduction

One challenge for realizing high-efficiency electrocatalysts for CO2 electroreduction is lacking in comprehensive understanding of potential-driven chemical state and dynamic atomic-configuration evolutions. Herein, by using a complementary combination of in situ/operando methods and employing copper single-atom electrocatalyst as a model system, we provide evidence on how the complex interplay among dynamic atomic-configuration, chemical state change and surface coulombic charging determines the resulting product profiles. We further demonstrate an informative indicator of atomic surface charge (φe) for evaluating the CO2RR performance, and validate potential-driven dynamic low-coordinated Cu centers for performing significantly high selectivity and activity toward CO product over the well-known four N-coordinated counterparts. It indicates that the structural reconstruction only involved the dynamic breaking of Cu–N bond is partially reversible, whereas Cu–Cu bond formation is clearly irreversible. For all single-atom electrocatalysts (Cu, Fe and Co), the φe value for efficient CO production has been revealed closely correlated with the configuration transformation to generate dynamic low-coordinated configuration. A universal explication can be concluded that the dynamic low-coordinated configuration is the active form to efficiently catalyze CO2-to-CO conversion.