Transfer Kinetics Research Articles

Oxygen vacancy-rich Fe2O3/Co3O4 heterostructure electrocatalyst promotes N2 activation for efficient nitrogen reduction

The adsorption and activation of N2 as well as the competitive hydrogen evolution reaction (HER) pose significant challenges to the electrocatalytic nitrogen reduction reaction (ENRR), which severely limits its industrial application. Therefore, exploring the ENRR electrocatalysts with high activity and selectivity is an extremely important task. In this work, the oxygen vacancy-rich Fe2O3/Co3O4 heterostructures (referred to as Vo-X-Fe2O3/Co3O4) were rationally designed by employing Co3O4 as a template via a simple hydrothermal and subsequent calcination method, which acted as highly efficient ENRR electrocatalysts. The electrocatalytic activity of Vo-X-Fe2O3/Co3O4 can be easily regulated by optimization of the Fe content and the introduction of oxygen vacancy (Vo). The results demonstrate that the optimized Vo-1.0-Fe2O3/Co3O4 catalyst achieves a high NH3 yield of 47.37μgh-1 mgcat-1 and a Faradaic efficiency (FE) of 22.42%. Moreover, the excellent stability and reproducibility are also demonstrated. The comprehensive characterizations reveal that the exceptional performance of Vo-1.0-Fe2O3/Co3O4 can be attributed to the improved N2 adsorption and activation, restricted competitive HER and promoted electron transfer kinetics induced by the synergistic introduction of Vo and Fe. This work emerged a new speculating orientation for rational design of ENRR catalysts.

Bimetallic Au-Ag Reduced Graphene Oxide Nanostructures for Enhanced Detection of Dengue Virus E Protein

The development of highly sensitive and specific diagnostic tools for early-stage detection of dengue virus (DENV) is critical for effective outbreak management, particularly in resource-limited settings. In this study, we report a novel electrochemical immunosensor based on bimetallic gold silver (Au-Ag) nanoparticles integrated with reduced graphene oxide (rGO) for the detection of dengue virus envelope (E) protein. The Au-Ag bimetallic nanostructures exhibit superior electron transfer kinetics and enhanced electrocatalytic activity, while rGO serves as an excellent platform due to its large surface area and high conductivity. This synergistic combination improves antigen-antibody interactions and significantly boosts sensor performance. The immunosensor demonstrated a broad linear detection range of 100 ag ml−1 to 10 ng ml−1, with a high correlation coefficient (R2 = 0.98519). It achieved an ultra-low limit of detection (LOD) of 4.959 ag ml−1 for DENV E protein, outperforming existing detection methods. These findings highlight the potential of the Au-Ag- rGO-based immunosensor as a promising tool for point-of-care diagnosis, enabling rapid and cost-effective disease management and control.

Physical and electrochemical performances of novel tellurium composite films as anode applications in energy storage systems

Portable electronic devices and electric cars use lithium-ion batteries, but clumping lithium alloys limit their lifespan. Due to their strong electronic conductivity, volumetric capacity, and high energy density, researchers are conducting research on electrochemical metal cells utilizing tellurium for high-performance batteries. Theoretically, lithium-tellurium batteries can improve energy densities three times more than lithium-ion batteries. However, metal-tellurium faces challenges such as low rate capability, unclear redox reactions, intermediate dissolution, and electrode volume changes. This study explores the enhancement of the energy storage capacity of next-generation batteries by fabricating coated electrode films as novel anodes from tellurium, silicon, and graphene. Physical, thermal, and morphological analysis of composite material are investigated by XRD, TEM, TGA, DSC, SEM, UV, and XPS analyses, revealing its rigidity as well as durability through its crystal structure alignment and thermal stability. In electrochemical analysis (CV) at various scan rates, samples that exhibit consistent and high specific capacity (Cp) values at different scan speeds (25, 50, and 100 mV/s) indicate excellent ability to store and maintain charge. Decreasing Cp values with increasing scan rates indicate that the speed of cycling limits the charge transfer kinetics and electrode performance. In EIS, the charge transfer resistances (Rct) for the pure Te, Te + Gr, Te + Si + Gr, and Te + Si samples are 759.07 Ω, 4.21 Ω, 36.39 Ω, and 164.90 Ω, respectively. The Te + Gr sample has the lowest Rct, indicating the best charge transfer efficiency at the electrode contact, whereas the Te + Si + Gr sample has a comparatively lower Rct, indicating better charge transfer kinetics. The combined result exhibits the synergistic impact of tellurium, silicon, and graphene in enhancing the energy storage capacity of future batteries across the industry.

Dependence of photocatalytic efficiency of titania-carbon nanotube nanocomposites on optoelectrical properties and colloidal stability

The correlation of photocatalytic efficiency of titania–amorphous (nitrogen doped) carbon nanotubes (TiO2–a(N)CNT) nanocomposites with colloidal and optoelectrical properties of the photocatalysts was investigated. TiO2–aNCNT and TiO2–aCNT exhibited narrow zeta potential variation, high polydispersity index, and large agglomerate size across the pH range 1–8. Despite the poor colloidal stability, TiO2–aNCNT exhibited superior degradation for high molecular weight reactive dyes, RR 120 and Remazol brilliant blue (RBB) with 55 mg.L−1 of RR 120 mineralized under solar irradiation. The photocatalytic performance for TiO2–aNCNT and TiO2–aCNT correlated with the respective energy band gaps 3.01 and 3.14 eV, Ubarch tailing energies. Cyclic voltammetry showed a narrow peak-to-peak separation (ΔEp) of 200.7 V (vs Ag/AgCl) for TiO2–aNCNT thus confirming enhanced electron transfer kinetics. Electron impedance spectroscopy confirmed low charge transfer resistance for TiO2–aNCNT. Herein it is demonstrated that optoelectrical properties are superior in driving photocatalytic reactions.

Triple S-scheme BiOBr@LaNiO3/CuBi2O4/Bi2WO6 heterojunction with plasmonic Bi-induced stability: deviation from quadruple S-scheme and mechanistic investigation

The investigation and understanding of heterointerfaces formation and charge transfer dynamics in two or more semiconductor heterojunctions increased ensuing establishment of S-scheme and dual S-scheme heterojunctions. However, investigations of possible charge transfer at interfaces and their type in four component systems are limited. Herein, a four-component heterojunction was investigated to postulate and demonstrate deviation between quadruple and triple S-scheme heterojunctions possibilities using LaNiO3, BiOBr, CuBi2O4, and Bi2WO6. DFT and XPS were used to construct the band structure and support the charge transfer at the interfaces to follow S-S strategy during OTC and SMX degradation under visible light. IEF, bend bending systematically modulated charge transfer, and the core-shell strategy restricted possible junctions’ formation to three to accord triple S-scheme heterojunction. This work demonstrated the construction of Triple S-scheme heterostructures as a promising strategy for efficient charge separation making it a suitable candidate for elimination of pollutants.

Light harvesting S-scheme g-C3N4/TiO2/M photocatalysts for efficient removal of hazardous moxifloxacin

The development of advanced photocatalysts with enhanced efficiency for environmental remediation is critical for addressing persistent organic pollutants like Moxifloxacin. In this study, we present a novel S-scheme heterojunction g-C3N4/TiO2/M photocatalyst designed to optimize light harvesting and charge separation for the effective degradation of Moxifloxacin. The innovative S-scheme configuration enables superior charge transfer dynamics by retaining potent photogenerated electrons in the conduction band of TiO2 and holes in the valence band of g-C3N4, significantly improving photocatalytic performance compared to conventional Type-II systems. Heterogeneous photocatalysis, particularly using TiO2-based materials, offers a promising approach. Here, we synthesized TiO2 hybridized with metal-doped g-C3N4 (GCNTM) via a simple hydrothermal method. The fabricated nanocomposites were characterized using SEM, XRD, FTIR, and UV–Vis (DRS). These GCNTM nanocomposites were employed for the degradation of hazardous Moxifloxacin (MXF) under visible light. Detailed analysis of the photocatalytic mechanism reveals that the synergistic interaction between g-C3N4, TiO2, and the co-catalyst M not only broadens the light absorption spectrum but also enhances the separation and lifespan of charge carriers. Among the synthesized materials, GCNTLa demonstrated the highest degradation efficiency, achieving 96 % removal of MXF. This enhanced activity is attributed to the effective suppression of charge recombination, leading to the generation of reactive species responsible for MXF degradation. Additionally, GCNTM showed remarkable stability and reusability, with only a 6 % reduction in efficiency after five cycles, confirming its high reusability and mechanical stability. Our S-scheme photocatalyst demonstrates a marked increase in the degradation rate of Moxifloxacin under visible light irradiation, highlighting its potential for practical environmental applications.

Investigating intermolecular interactions of surfactant solutions using femtosecond thermal lens spectroscopy

In this study, we examined the impact of various surfactants (oleic acid, butyric acid, Span-20, and CTAB) on the thermophysical properties of methanol (MeOH) using a femtosecond laser-induced thermal lens (TL) spectroscopic technique. Methanol was chosen for its unique convective properties under intense localized heating, making it a promising candidate for studying photothermal responses. We discovered that the TL characteristics of both pure methanol and methanol-surfactant mixtures are significantly influenced by the molecular interactions and physical properties of the components. Our experimental results indicate that the addition of surfactants notably alters the heat transfer dynamics of the solvent by restricting natural molecular movement and modifying thermal properties, which in turn affect the TL signatures. Beyond the surfactant concentration, we observed that the extent of variation in steady-state TL signals, inflection points, and heat transfer mechanisms depends on the molecular properties of the surfactants, such as chain length, the number of active (hydrophilic) groups per molecule, thermal conductivity, viscosity, and intermolecular interactions. Our TL findings provide a detailed investigation into the effect of surfactants on the photothermal response and heat transfer process of a solvent for the first time.

Analytical prediction model for edge water invasion flow rate in SAGD heavy oil reservoirs

SAGD (Steam Assisted Gravity Drainage) technology is a highly developed method for the extracting heavy oil. In the Liaohe Oilfield in China, there are 72 SAGD well groups within a massive heavy oil reservoir containing edge water and the risk associated with edge water invasion is substantial. Currently, the injected steam is less than 50 m away from the edge water, which increases the urgency to address the potential invasion of edge water. If the edge water flows into the reservoir, it will impact nearly 8.0 × 105 tons of crude oil production. Recognizing the importance of mitigating the edge water invasion, this paper proposes a prediction model for the edge water invasion flow rate in SAGD reservoirs. The model integrates mass and heat transfer dynamics between the steam chamber and edge water, the relative permeabilities of oil and water phases, and the viscosity-temperature relationship of water. The model is validated through numerical simulations and field data. The findings indicate that for SAGD reservoirs with a permeability greater than 1 D, maintaining a minimum distance of 25 m between the edge water and the steam chamber is advisable, especially when the pressure differential is 0.5 MPa. Furthermore, the prediction model is used to forecast the edge water breakthrough time and evaluate water invasion risk. A prediction chart for the edge water invasion flow rate is developed, providing a practical tool for estimating invasion flow rate curves. Also, a method of edge water invasion warning is established, with a corresponding chart that offers a quick assessment of water invasion risks in heavy oil reservoirs. Overall, this research lays a foundational framework for understanding and managing the edge water invasion in SAGD operations, offering critical insights for the future study aimed at addressing the challenge posed by edge water in heavy oil reservoirs.

Unveiling Spatial and Temporal Dynamics of Plasmon-Enhanced Localized Fields in Metallic Nanoframes through Ultrafast Electron Microscopy.

Plasmonic nanomaterials, particularly noble metal nanoframes (NFs), are important for applications such as catalysis, biosensing, and energy harvesting due to their ability to enhance localized electric fields and atomic efficiency via localized surface plasmon resonance (LSPR). Yet the fundamental structure-function relationships and plasmonic dynamics of the NFS are difficult to study experimentally and thus far rely predominately on computational methodologies, limiting their utilization. This study leverages the capabilities of ultrafast electron microscopy (UEM), specifically photon-induced near-field electron microscopy (PINEM), to probe the light-matter interactions within plasmonic NF structures. The effects of shape, size, and plasmonic coupling of Pt@Au core-shell NFs on spatial and temporal characteristics of plasmon-enhanced localized electric fields are explored. Importantly, time-resolved PINEM analysis reveals that the plasmonic fields around hexagonal NF prisms exhibit a spatially dependent excitation and decay rate, indicating a nuanced interplay between the spatial geometry of the NF and the temporal evolution of the localized electric field. These results and observations uncover nanophotonic energy transfer dynamics in NFs and highlight their potential for applications in biosensing and photocatalysis.

Adsorption of Thiotepa on B12N12, Mg12O12, and Si12C12 Fullerene-like Cages: A DFT Study

We examined the adsorption of thiotepa (TTP) on the outer surface of B12N12, Mg12O12, and Si12C12 fullerene-like cages using density functional theory (DFT) calculations. The computations were carried out at the Perdew-Burke-Ernzerhof level with the D3 dispersion correction (PBE-D3) in a water solvent. The adsorption mechanism of TTP through N-head and S-head on the external surface of Si12C12 involves a covalent interaction (binding energy ∼ -1.31 eV) with the carrier surface. In contrast, the adsorption of the TTP molecule through N-head and S-head on the outer surfaces of B12N12 (binding energy ∼ -0.75 eV) and Mg12O12 (binding energy ∼ -0.62 eV) fullerene-like cages is driven by electrostatic interactions. Therefore, due to their low values of recovery time, both B12N12 and Mg12O12 fullerene-like cages can serve as carriers for TTP in the treatment of cancer. Thermodynamic parameters (Gibbs free energy and enthalpy energy) demonstrate that these interactions are exothermic and spontaneous. The results further reveal the significant disparity in the calculated HOMO and LUMO energies at the computational level. The formation of intricate bonds between the drug and the fullerene-like cages is attributed to the charge transfer dynamics that occur during their interactions. Through computational analysis and examination of the total density of state (TDOS) plots, it is evident that B12N12 and Si12C12 fullerene-like cages exhibit a high degree of sensitivity to the TTP drug. The adsorption process can increase the electrical conductivity of B12N12 and Si12C12, while having minimal effect on Mg12O12. This suggests that B12N12 could potentially serve as a suitable biosensor for detecting TTP.

A self-supporting nanoflower-like film of 3D walnut shell derived carbon/NiCo2S4 for supercapacitors and zinc-ion batteries with high energy density

Nanocomposites with special structures can generally provide more efficient electron and ion transfer kinetics during electrochemical charge storage, resulting in satisfactory energy densities. Herein, we adopted a simple hydrothermal method to prepare a nanoflower-like NiCo2S4 growing on hierarchical porous N, O co-doped walnut shell-derived carbon (10-WSC-N/O@NiCo2S4). Metal ions (Ni2+, Co2+) enhanced the active site to obtain better electrochemical activity, as well as the porous carbon framework helped achieve better ion transport and electron conduction. Importantly, 10-WSC-N/O@NiCo2S4 exhibits 1176 F g−1 at 0.5 A g−1, the prepared 10-WSC-N/O@NiCo2S4//WSC-N/O displays a remarkable energy density of 68.6 Wh kg−1 at 375 W kg−1 and only decreases a 12 % in capacitance after 8000 cycles at 3.0 A g−1. Additionally, the 10-N/O@NiCo2S4//Zn device achieves a high energy density of 88.54 Wh kg−1 at 750 W kg−1. Overall, this work provides an efficient strategy for fabricating high-performance electrode materials.

Modulating Eco-friendly Colloidal AgGaS2 Quantum Dots for Highly Efficient Photodetection and Image Sensing via Direct Growth of Ternary AgInS2 Shell.

Tailoring the optoelectronic characteristics of colloidal quantum dots (QDs) by constructing a core/shell structure offers the potential to achieve high-performing solution-processed photoelectric conversion and information processing applications. In this work, the direct growth of wurtzite ternary AgInS2 (AIS) shell on eco-friendly AgGaS2 (AGS) core QDs is realized, giving rise to broadened visible light absorption, prolonged exciton lifetime and enhanced photoluminescence quantum yield (PLQY). Ultrafast transient absorption spectroscopy demonstrats that the photoinduced carrier separation and transfer kinetics of AGS QDs are significantly optimized following the AIS shell coating. As-synthesized environmentally benign AGS/AIS core/shell QDs are employed to fabricate photodetectors (PDs), showing a remarkable responsivity of 38.4 AW-1 and a detectivity of 2.4×1012 Jones under visible light illumination (405 nm). Moreover, the fabricated QDs-PDs exhibit superior image-sensing capability to record complex patterns with high resolution (160×160 pixels) under visible light illumination at 405 and 532 nm. The findings indicate that the direct growth of multinary narrow-band shell materials on eco-friendly QDs holds great promise to implement future "green", cost-effective and high-performance optoelectronic sensing/imaging systems.

Mpsqd: A matrix product state based Python package to simulate closed and open system quantum dynamics.

We introduce a Python package based on matrix product states (MPS) to simulate both the time-dependent Schrödinger equation (TDSE) and the hierarchical equations of motion (HEOM). The wave function in the TDSE or the reduced density operator/auxiliary density operators in the HEOM are represented using MPS. A matrix product operator (MPO) is then constructed to represent the Hamiltonian in the TDSE or the generalized Liouvillian in the HEOM. The fourth-order Runge-Kutta method and the time-dependent variational principle are used to propagate the MPS. Several examples, including the nonadiabatic interconversion dynamics of the pyrazine molecule, excitation energy transfer dynamics in molecular aggregates and photosynthetic light-harvesting complexes, the spin-boson model, a laser driven two-state model, the Holstein model, and charge transport in the Anderson impurity model, are presented to demonstrate the capability of the package.

Harnessing the potential of MOF/Fe2O3 nanocomposite within polypyrrole matrix for enhanced hydrogen evolution

This study investigates the influence of pyrrole concentration and the addition of MIL53(Al)/Fe2O3 nanocomposite on the hydrogen evolution reaction (HER) activity of polypyrrole (PPy) electrocatalysts. Electrodeposition of PPy on a nickel (Ni) substrate was conducted using various pyrrole concentrations ranging from 0.01 M to 0.2 M, followed by evaluation through linear sweep voltammetry (LSV) experiments. Results indicated that PPy synthesized with 0.1 M pyrrole exhibited the highest HER activity, characterized by lower onset potential and higher current density. Additionally, the incorporation of MIL53(Al)/Fe2O3 nanocomposite into PPy coating enhanced electrode performance, evidenced by high charge transfer kinetics. Nyquist diagrams and electrochemical impedance spectroscopy (EIS) analysis confirmed accelerated electron transfer kinetics and lower charge transfer resistance for PPy@MIL53(Al)/Fe2O3 compared to Ni substrate. Despite a lower electrochemical double layer capacitance (Cdl), PPy@MIL53(Al)/Fe2O3 demonstrated enhanced catalytic activity, underscoring the importance of electrode morphology and active site characteristics. Furthermore, stability tests revealed consistent performance of PPy@MIL53(Al)/Fe2O3 over prolonged electrolysis periods, highlighting its potential for practical applications in hydrogen generation.

Low-crystalline 1T/2H-MoSe2 heterostructure as the high-rate and ultra-long-lifespan cathode materials for magnesium ion batteries

Two-dimensional layered-like materials are attracted extensive attention to be the potential cathode materials for magnesium ion batteries because of the wide layer distances and high capacities. Whereas such strong interaction between bivalent Mg2+ and layered cathode materials is prone to cause the slow diffusion kinetics, and irreversible electrochemical reaction, finally bringing about the low specific capacity and inferior rate capability. Meanwhile, limited by the inherent crystal structure of MoSe2 and unsuitable electrolyte, the magnesium storage properties are not ideal. Herein, the low-crystalline 1T/2H-MoSe2 heterostructure (LC-MoSe2) is synthesized via one-step hydrothermal method. Such low-crystalline feature of LC-MoSe2 and MgCl+ in the electrolyte significantly decrease the Mg2+ diffusion barrier, and largely promote the Mg2+ diffusion kinetics. The rich heterogeneous interfaces in the 1T/2H-MoSe2 boost the electron/ion transfer kinetics and endow plentiful active sites for the Mg2+ storage. As expected, the LC-MoSe2 exhibits a high discharge capacity (257.4 mAh g−1/0.5 A g−1/200 cycles) and stable long-span cyclic life of 2000/1000 loops even at 2/5 A g−1, distinctly transcending those of relatively high-crystalline MoSe2 (HC-MoSe2). Such electrode can also surprisingly cycle at an ultra-high rate of 10 A g−1. Meanwhile, the charge transfer/ion diffusion kinetics along with charge storage mechanism of LC-MoSe2 are carried out by various kinetics strategies from experimental and theoretical aspects. The reaction mechanism has also been discussed by some ex-situ characterization techniques. The remarkable Mg2+ storage properties of LC-MoSe2 cathode materials provide new ideas for the long-run development of MIBs.

Moment analysis method for the determination of permeation kinetics of coumarin at lipid bilayers of liposomes by using capillary electrophoresis.

A method was developed for studying mass transfer kinetics at lipid bilayers of liposomes. Elution peaks of coumarin were measured by liposome electrokinetic chromatography (LEKC). Four types of phospholipids having different alkyl chains were used for preparing liposomes, which were used as pseudo-stationary phases in LEKC systems. Rate constants of permeation across lipid bilayers of liposomes or of adsorption at lipid membranes were determined by analyzing the first absolute and second central moments of the elution peaks measured by LEKC. The rate constants of permeation or adsorption tend to decrease with an increase in the carbon number of the alkyl chains of phospholipids. It was demonstrated that the moment analysis of elution peak profiles measured by LEKC is effective for determining lipid membrane permeability or adsorption kinetics. Compared with other conventional techniques, the method has some advantages for studying mass transfer kinetics at lipid bilayers. Solute permeation across or solute adsorption at real lipid bilayers of liposomes is analyzed. The principle of the method is the analysis of separation behavior in LEKC, which is different from that of the other ones. It is expected that the method contributes to the kinetic study of mass transfer at lipid bilayers from various perspectives.

Push-Pull Electrolyte Design Strategy Enables High-Voltage Low-Temperature Lithium Metal Batteries.

Lithium (Li) metal batteries hold significant promise in elevating energy density, yet their performance at ultralow temperatures remains constrained by sluggish charge transport kinetics and the formation of unstable interphases. In conventional electrolyte systems, lithium ions are tightly locked in the solvation structure, thereby engendering difficulty in the desolvation process and further exacerbating solvent decomposition. Herein, we propose a new push-pull electrolyte design strategy, utilizing molecular electrostatic potential (ESP) screening to identify 2,2-difluoroethyl trifluoromethanesulfonate (DTF) as an optimal cosolvent. Importantly, DTF exhibits a moderate ESP minimum (-21.0 kcal mol-1) to strike a balance between overly strong and overly weak Li ion affinity, which allows the sulfonyl group to effectively pull Li ions without disrupting the anion-rich solvation structure. Simultaneously, the difluoromethyl group, with a high ESP maximum (37.3 kcal mol-1), pushes solvent molecules via competitive hydrogen bonding. This design reconstructs existing solvation structures and expedites Li ion desolvation. Furthermore, fluorinated DTF demonstrates excellent stability at elevated voltage and facilitates the formation of robust inorganic-rich interphases. Impressively, rapid charge transfer kinetics can be achieved employing designed electrolyte, and the LiNi0.8Mn0.1Co0.1O2 (NMC811)||Li cells demonstrate excellent charge-discharge cycling stability with a high capacity exceeding 153 mAh g-1 even at -40 °C, retaining over 93% of initial capacity after 100 cycles under a 4.8 V charging cutoff. This work provides insights into the design of low-temperature electrolytes with a wide electrochemical window, advancing the development of batteries for extreme conditions.

Synthesis and Understanding of the Role of Donor-Tetracyanobutadiene in Porphyrin β-Periphery toward Ultrafast Charge Transfer Dynamics

Synthesis and Understanding of the Role of Donor-Tetracyanobutadiene in Porphyrin β-Periphery toward Ultrafast Charge Transfer Dynamics

Theoretical Investigation on Proton Transfer Directionality and Dynamics Behavior of 3-(Benzo[d]thiazol-2-yl)-2-hydroxy-5-methoxybenzaldehyde with Two Asymmetric Proton Acceptors.

A detailed theoretical investigation on the excited state intramolecular proton transfer (ESIPT) directionality and dynamics behavior of 3-(benzo[d]thiazol-2-yl)-2-hydroxy-5-methoxybenzaldehyde (BTHMB) with two unsymmetric proton acceptors (N and O2) has been performed. The hydrogen bond O1-H···N in BTHMB-a formed by the O1-H group with the N atom or O1-H···O2 in BTHMB-b formed by the O1-H group with the O2 atom is enhanced upon photoexcitation, and the strength of the O1-H···N bond is stronger, which will drive the O1-H proton to the N atom. Potential energy curves further confirm that ESIPT occurs in the N atom because of the smaller energy barrier (0.39 kcal/mol). Results of dynamics simulations manifest that no surface hopping exists between the S0 and S1 states within 300 fs, and ESIPT time constants of BTHMB-a and BTHMB-b are 48 and 151 fs, respectively. While the reverse ESIPT is observed in BTHMB-b at 294 fs, implying that the O1-H proton is transferred to the N atom instead of the O2 atom. The consistency of the calculated absorption (390 nm) and fluorescence spectra (443 and 602 nm) of BTHMB-a with the experimental values (390, 410, and 605 nm) confirms this conclusion again. The charge distribution analysis shows that the charge on the proton acceptors increases, and the O2 atom has higher electronegativity because it has more negative charges. The minimum surface electrostatic potential on the N atom in BTHMB-b correlating with the pKb value is -47.38 kcal/mol, indicating that the N atom has strong basicity. Therefore, the basicity of the N atom dominates the ESIPT process rather than the electronegativity of the O2 atom.

Non-steady flow decomposition behaviors of heat and mass transfer on intrinsic kinetics for methane hydrate particles transported in pipelines

The differential equations governing the decomposition rate and activation energy, convective mass transfer, methane diffusion and fugacity, as well as heat conduction and enthalpy change were derived by integrating thermal convection, heat conduction, mass transfer and intrinsic kinetics. Mathematical models for decomposition kinetics and thermodynamics in a non-steady field were solved using a radial logarithmic grid for node division and discretization of the equations. The study elucidated the heat and mass transfer processes as well as decomposition kinetics in pipelines by analyzing the impacts of particle size, temperature, pressure, flow rate and activation energy on decomposition rate. The results indicated that compared with the isothermal decomposition of the intrinsic kinetic model and static experimental decomposition, the complex non-steady multiphase flow model offers a more accurately simulation of hydrate decomposition as well as associated heat and mass transfer processes. Hydrate decomposition is characterized as a non-isothermal dynamic ablation process with heat transfer rate and intrinsic kinetics dominating during the preliminary stage and the stable stage, respectively. An increasing in the slurry temperature, temperature fluctuation and flow rate accelerated the heat transfer rate capacity, enhanced convective heat transfer capacity and facilitated hydrate decomposition, with the mass transfer rate exhibiting lesser influence. The particle surface area and slurry temperature exhibited the most significant influence on hydrate decomposition, which was followed by flow rate. Upon increasing particle size from 1 mm to 5 mm and the temperature from 293 K to 313 K, the decomposition rate increased by 20.7 times and 13.5 times, respectively. Furthermore, enhancing temperature and flow rate while decreasing particle size and pressure decreased both the decomposition time and the duration required for the decomposition rate to reach its peak. Additionally, the decomposition rate and its constant vary with the activation energy.