Search Results (2,164)

Electrochemical reduction processes enable the CO to be converted into a useful chemical fuel. Our study employs density functional theory calculations to analyze the (110) facets of the transition metal carbide surfaces for CO capture, incorporating the Mars–van Krevelen (MvK) mechanism. All the possible adsorption sites on the surface, including carbon, metal, and bridge sites, were fully investigated. The findings indicate that the carbon site is more active relative to the other adsorption sites examined. The CO hydrogenation paths have been comprehensively investigated on all the surfaces, and the free energy diagrams have been constructed towards the product. The results conclude that the TiC is the most promising candidate for the formation of methane, exhibiting an onset potential of −0.44 V. The predicted onset potential for CrC, MoC, NbC, VC, WC, ZrC, and HfC are −0.86, −0.61, −0.61, −0.93, −0.87, −0.61, and −0.81 V, respectively. Our calculated results demonstrate that MvK is selectively relevant to methane synthesis. Additionally, we investigated the stability of these surfaces against decomposition and conversion to pure metals concerning thermodynamics and kinetics. It was found that these carbides could remain stable under ambient conditions. The exergonic adsorption of hydrogen on carbon sites, requiring smaller potential values for product formation, and stability against decomposition indicate that these surfaces are highly suitable for CO reduction reactions using the MvK mechanism. Full article

In this study, blue fluorescence carbon dots of high quantum yield (42.96%) were successfully synthesized via a one-step hydrothermal method using Pueraria residues as the precursor and urea as the nitrogen source. The preparation process was simple, was environmentally friendly, and did not use toxic chemicals, with the resulting nitrogen-doped Pueraria carbon dots (N-PCDs) exhibiting excellent dispersibility, regular morphology and stable fluorescence performance. Moreover, fluorescence quenching could be induced through electron transfer between N-PCDs and hexavalent chromium (Cr(VI)) in water, which enabled the application of N-PCDs as a fluorescent probe for sensing Cr(VI) in water, with a limit of detection (LOD) and limit of quantitation (LOQ) of 0.078 μM and 0.26 μM, respectively. The effectiveness of the proposed fluorescent probe was also validated in various water matrices, achieving stable recovery rates ranging from 98.7% to 101.5%. Furthermore, experimental investigations and theoretical calculations through density functional theory (DFT) confirmed that the underlying reaction mechanism was photoinduced electron transfer (PET). Above all, this study not only demonstrated the potential of N-PCDs as sensitive probes to sense toxic elements in the environment, but also promotes the green and scalable production of high-value carbon-based products from waste biomass. Full article

Room-temperature sodium–sulfur (RT Na-S) batteries hold great potential in the field of large-scale energy storage due to their high theoretical energy density and low cost of raw materials. However, the inherent low conductivity, notorious shuttling, and sluggish kinetics of cathode materials cause the loss of active substances and capacity delay, hindering the practical application of RT Na-S batteries. Owing to their low cost, variable oxidation states, and unsaturated d orbitals, transition metal (TM)-based catalysts have been extensively studied in circumventing the above shortcomings. Herein, the review first elaborates on the reaction mechanisms and current challenges of RT Na-S batteries. Subsequently, the role and function mechanism of TM-based catalysts (including single/dual atoms, nanoparticles, compounds, and heterostructures) in RT Na-S batteries are described. Specifically, based on the theories of electronic transfer and atomic orbital hybridization, the interaction mechanism between TM-based catalysts and polysulfides, as well as the catalytic performance, are systematically discussed and summarized. Finally, a discussion on the challenges and future research perspectives associated with TM-based catalysts for RT Na-S batteries is provided. Full article

The adsorption of gas reactant molecules (H₂, CO, etc.) to the surface of hematite is the premise of chemical reaction. In order to further promote the basic research on the reaction mechanism of hematite reduction by a H₂-CO gas mixture, the adsorption behavior of H₂ (or CO) under the conditions of pre-adsorbed H₂O (or CO₂) was systematically studied by the density functional theory (DFT) combined with reduction experiments. The results indicate that the gas molecules (H₂, CO, H₂O and CO₂) adsorbed on the Fe atom of the Fe₂O₃ (001) surface rather than the O atom, and the adsorption energy of the Fe₂O₃-CO adsorption system was relatively minimum (−1.317 eV), indicating that the Fe₂O₃-CO adsorption system was more stable. In addition, the adsorption energy of the H₂ molecule adsorbed to the Fe₂O₃-H₂O adsorption system was −0.132 eV, which was smaller than that of the H₂ molecule directly adsorbed to Fe₂O₃ (−0.013 eV), indicating that the H₂O molecule pre-adsorption was beneficial to the H₂ molecule adsorption. Compared with the H₂O molecule, the CO₂ molecule had relatively less influence on the adsorption and subsequent behavior of CO with Fe₂O₃. From the experiment analysis results, on the whole, CO₂ had a greater impact on the gas diffusion, while H₂O had a greater impact on the interfacial chemical reaction (gas adsorption), which was consistent with the DFT calculation results. Full article

Reported rate constants of charge transfer reactions (CTs) have ranged widely, depending on techniques and timescales. This fact can be attributed to the time-dependent double-layer capacitance (DLC), caused by solvent interactions such as hydrogen bonds. The time variation of the DLC necessarily affects the heterogeneous electrode kinetics. The delay by the solvation, being frequency dispersion, is incorporated into the CT kinetics in this report on the basis of the conventional reaction rate equations. It is different from the absolute rate theory. This report insists on a half value of the transfer coefficient owing to the segregation of the electrostatic energy from the chemical one. The rate equation here is akin to the Butler–Volmer one, except for the power law of the time caused by the delay of the DLC. The dipoles orient successively other dipoles in a group associated with the delay, which resembles that in the DLC. The delay suppresses the observed currents in the form of a negative capacitance. The above behavior was examined with a ferrocenyl derivative by ac impedance methods. The delay from diffusion control was attributed to the negative capacitance rather than the CT, even if the conventional DLC effect was corrected. Full article

Alongside the gradual progress of industrialization and the continuous development of human society, the problems of environmental pollution and energy crisis have become increasingly prominent. Semiconductor photocatalysis is a promising solution to these challenges. The photocatalytic reduction of CO₂ by TiO₂ to produce carbon monoxide and methane is a process which has been identified as a means of developing clean energy. In this paper, two-dimensional TiO₂ (2D-TiO₂) was synthesized via a one-step solvothermal method, and one-dimensional TiO₂ (1D-TiO₂) was obtained through a hydrothermal process. Their photocatalytic CO₂ reduction performances were systematically investigated. The results show that 2D-TiO₂ exhibits superior catalytic activity compared to 1D-TiO₂, which can be attributed to its lamellar structure, larger specific surface area, and improved hydrophilicity, providing more active sites and faster reaction kinetics. To further reveal the reaction mechanism, density functional theory (DFT) calculations were carried out using VASP with the GGA–PBE functional, PAW potentials, and a plane-wave cutoff energy of 520 eV. A 3 × 3 × 1 Monkhorst–Pack grid was used for Brillouin zone integration, and all possible adsorption configurations of CO₂*, COOH*, and CO* intermediates on the 2D-TiO₂ surface were evaluated. The results confirm that 2D-TiO₂ stabilizes key intermediates more effectively, thereby lowering the energy barrier and facilitating CO₂ reduction. These findings demonstrate that structural modulation of TiO₂ significantly influences its photocatalytic performance and highlight the great potential of 2D-TiO₂ for efficient CO₂ conversion and clean energy applications. Full article

In the polyurethane industry, catalytically generated carbodiimides can modify the properties of isocyanate and, thus, the resulting foams. In this work, a kinetic reaction study was carried out to investigate the formation of a simple, bifunctional carbodiimide from a widely used polyurethane raw material: 4,4′-methylenediphenyl diisocyanate (MDI). The experimental section outlines a catalytic process, using a 3-methyl-1-phenyl-2-phospholene-1-oxide (MPPO) catalyst in ortho-dichlorobenzene (ODCB) solvent, to model industrial circumstances. The reaction produces carbon dioxide, which was observed using gas volumetry at between 50 and 80 °C to obtain kinetic data. A detailed regression analysis with linear and novel nonlinear fits showed that the initial stage of the reaction is second-order, and the temperature dependence of the rate constant is $k(T)=(3.4\pm 3.8)\mathrm{‧}{10}^6\cdot e^{{\displaystyle \frac{-7192\pm 389}{T}}}$. However, the other isocyanate group of MDI reacts with new isocyanate groups and the reaction deviates from the second-order due to oligomer (polycarbodiimide) formation and other side reactions. A linearized Arrhenius equation was used to determine the activation energy of the reaction, which was E_a = 60.4 ± 3.0 kJ mol⁻¹ at the applied temperature range, differing by only 4.6 kJ mol⁻¹ from a monoisocyanate-based carbodiimide. In addition to experimental results, computationally derived thermochemical data (from simplified DFT and IRC calculations) were applied in transition state theory (TST) for a comprehensive prediction of rate constants and Arrhenius parameters. As a result, it was found that the activation energy of the carbodiimide bond formation reaction from theoretical and experimental results was independent of the number and position of isocyanate groups, which is consistent with the principle of equal reactivity of functional groups. Full article

Supercritical CO₂ (ScCO₂) injection has emerged as a promising method to enhance shale gas recovery while simultaneously achieving CO₂ sequestration. This research investigates how ScCO₂ interacts with water and shale rock, altering the pore structure characteristics of shale reservoirs. The study examines shale samples from three marine shale formations in southern China under varying thermal and pressure regimes simulating burial conditions at 1000 m (45 °C and 10 MPa) and 2000 m (80 °C and 20 MPa). The research employs multiple analytical techniques including XRD for mineral composition analysis, MICP, N₂GA, and CO₂GA for comprehensive pore characterization, FE–SEM for visual observation of mineral and pore changes, and multifractal theory to analyze pore structure heterogeneity and connectivity. Key findings indicate that ScCO₂–water–shale interactions lead to dissolution of minerals such as kaolinite, calcite, dolomite, and chlorite, and as the reaction proceeds, substantial secondary mineral precipitation occurs, with these changes being more pronounced under 2000 m simulation conditions. Mineral dissolution and precipitation cause changes in pore structure parameters of different pore sizes, with macropores showing increased PV and decreased SSA, mesopores showing decreased PV and SSA, and micropores showing insignificant changes. Moreover, mineral precipitation effects are stronger than dissolution effects. These changes in pore structure parameters lead to alterations in multifractal parameters, with mineral precipitation reducing pore connectivity and consequently enhancing pore heterogeneity. Correlation analysis further revealed that H and D₋₁₀–D₁₀ exhibit a significant negative correlation, confirming that reduced connectivity corresponds to stronger heterogeneity, while mineral composition strongly controls the multifractal responses of macropores and mesopores, with micropores mainly undergoing morphological changes. However, these changes in micropores are mainly manifested as modifications of internal space. Siliceous shale samples exhibit stronger structural stability compared to argillaceous shale, which is attributed to the mechanical strength of the quartz framework. By integrating multifractal theory with multi–scale pore characterization, this study achieves a unified quantification of shale pore heterogeneity and connectivity under ScCO₂–water interactions at reservoir–representative pressure–temperature conditions. This novelty not only advances the methodological framework but also provides critical support for understanding CO₂–enhanced shale gas recovery mechanisms and CO₂ geological sequestration in depleted shale gas reservoirs, highlighting the complex coupling between geochemical reactions and pore structure evolution. Full article

Single-atom catalysts supported by two-dimensional materials have been widely used in the electrochemical CO₂ reduction reaction (CO₂RR). Defects are inevitably generated during the preparation of two-dimensional materials. In this study, six Fe–N₄-doped graphene catalysts (CAT1–CAT6) containing single carbon vacancy defects were designed and calculated using density functional theory (DFT) calculations. The stability, catalytic activity and product selectivity of these catalysts for CO₂RR to C₁ products CO, HCOOH, CH₃OH and CH₄ were discussed and compared with the defect-free Fe−N₄-doped graphene catalyst (CAT0). The results show that CAT1–CAT6 all exhibit excellent thermodynamic and electrochemical stabilities. The possible reaction pathways for CO₂ reduction to different C₁ products were systematically investigated. The CAT2, CAT3 and CAT6 exhibit high selectivity for HCOOH, whereas the products of CAT1, CAT4 and CAT5 are HCOOH, CH₃OH and CH₄, the same as those of CAT0. Moreover, these six catalysts more effectively suppress the competing hydrogen evolution reaction (HER) compared to CAT0, indicating that the defect improves the catalytic selectivity of CO₂RR. Among all of the catalysts, CAT2 demonstrates the most prominent catalytic activity and selectivity toward the CO₂ reduction reaction (CO₂RR). The large distortion of Fe−N₄ in *HCOO with CAT2 contributes to the lower limiting potential U_L. We hope that the finding that the large distortion of Fe−N₄ could lower the limiting potential will provide theoretical insights for the design of more efficient CO₂RR electrocatalysts. Full article

A methane-air premixed gas explosion is one of the most destructive disasters in the process of coal mining, and the dynamic coupling between the shock wave triggered by the explosion and the surrounding rock of the roadway can lead to the destabilization of the surrounding rock structure, the destruction of equipment, and casualties. The aim of this study is to systematically reveal the propagation characteristics of the blast wave, the spatial and temporal evolution of the wall load, and the damage mechanism of the surrounding rock by establishing a two-way fluid-solid coupling numerical model. Based on the Ansys Fluent fluid solver and Transient Structure module, a framework for the co-simulation of the fluid and solid domains has been constructed by adopting the standard $k-\epsilon$ turbulence model, finite-rate/eddy-dissipation (FR/ED) reaction model, and nonlinear finite-element theory, and by introducing a dynamic damage threshold criterion based on the Drucker–Prager and Mohr–Coulomb criteria. It is shown that methane concentration significantly affects the kinetic behavior of explosive shock wave propagation. Under chemical equivalence ratio conditions (9.5% methane), an ideal Chapman–Jouguet blast wave structure was formed, exhibiting the highest energy release efficiency. In contrast, lean ignition (7%) and rich ignition (12%) conditions resulted in lower efficiencies due to incomplete combustion or complex combustion patterns. In addition, the pressure time-history evolution of the tunnel enclosure wall after ignition triggering exhibits significant nonlinear dynamics, which can be divided into three phases: the initiation and turbulence development phase, the quasi-steady propagation phase, and the expansion and dissipation phase. Further analysis reveals that the closed end produces significant stress aggregation due to the interference of multiple reflected waves, while the open end increases the stress fluctuation due to turbulence effects. The spatial and temporal evolution of the strain field also follows a three-stage dynamic pattern: an initial strain-induced stage, a strain accumulation propagation stage, and a residual strain stabilization stage and the displacement is characterized by an initial phase of concentration followed by gradual expansion. This study not only deepens the understanding of methane-air premixed gas explosion and its interaction with the roadway’s surrounding rock, but also provides an important scientific basis and technical support for coal mine safety production. Full article

The persistence of pharmaceutical pollutants such as ciprofloxacin (CIP) in aquatic environments represents a critical environmental threat due to their potential to induce antimicrobial resistance. Photocatalysis using TiO₂-based materials offers a promising solution for their mineralization; however, the limited visible-light response of TiO₂ and charge carrier recombination restricts its overall efficiency. In this study, Nb-doped TiO₂ nanoparticles were synthesized via the sol–gel method, incorporating Nb⁵⁺, ions into the TiO₂ lattice to modulate the structural and electronic properties of TiO₂ to enhance its photocatalytic performance for CIP degradation under UV and visible irradiation. Comprehensive structural, morphological, and optical analyses revealed that Nb incorporation stabilizes the anatase phase, reduces particle size (from 21.42 nm to 10.29 nm), and induces a slight band gap widening (from 2.85 to 2.87 eV) due to the Burstein–Moss effect. Despite this blue shift, Nb-TiO₂ exhibited significantly improved photocatalytic activity under visible light, achieving 86% CIP degradation with a reaction rate 16 times higher than that of undoped TiO₂. This enhancement was attributed to improved charge separation and higher hydroxyl radical (^•OH) generation, driven by excess conduction band electrons introduced by Nb doping. Density Functional Theory (DFT) calculations further elucidated the electronic structure modifications responsible for this behavior, offering molecular-level insights into Nb dopant-induced property tuning. These findings demonstrate how targeted doping strategies can engineer multifunctional nanomaterials with superior photocatalytic efficiencies, especially under visible light, highlighting the synergy between experimental design and theoretical modeling for environmental applications. Full article

Carbon dioxide is naturally present in the Earth’s atmosphere and plays a role in regulating and balancing the planet’s temperature. However, due to various human activities, the amount of carbon dioxide is increasing beyond safe limits, disrupting the Earth’s natural temperature regulation system. Today, CO₂ is the most prevalent greenhouse gas; as its concentration rises, significant climate change occurs. Therefore, there is a need to utilize anthropogenically released carbon dioxide in valuable fuels, such as formic acid (HCOOH). Single-atom catalysts are widely used, where a single metal atom is anchored on a surface to catalyze chemical reactions. In this study, we investigated the potential of Cu@Phosphorene as a single-atom catalyst (SAC) for CO₂ reduction using quantum chemical calculations. All computations for Cu@Phosphorene were performed using density functional theory (DFT). Mechanistic studies were conducted for both bimolecular and termolecular pathways. The bimolecular mechanism involves one CO₂ and one H₂ molecule adsorbing on the surface, while the termolecular mechanism involves two CO₂ molecules adsorbing first, followed by H₂. Results indicate that the termolecular mechanism is preferred for formic acid formation due to its lower activation energy. Further analysis included charge transfer assessment via NBO, and interactions between the substrate, phosphorene, and the Cu atom were confirmed using quantum theory of atoms in molecules (QTAIM) and non-covalent interactions (NCI) analysis. Ab initio molecular dynamics (AIMD) calculations examined the temperature stability of the catalytic complex. Overall, Cu@Phosphorene appears to be an effective catalyst for converting CO₂ to formic acid and remains stable at higher temperatures, supporting efforts to mitigate climate change. Full article

Background/Objectives: Patients with erythropoietic protoporphyria (EPP) have a decreased activity of the ferrochelatase enzyme which converts protoporphyrin IX (PpIX) into heme, causing PpIX to accumulate in erythrocytes. The ensuing release of PpIX to the skin when exposed to visible light causes a phototoxic reaction with severe pain, erythema, and edema. Erythrocyte PpIX levels in adult EPP patients are rather stable and largely unaffected by pharmaceutical treatments. It is important to be aware of drugs causing an increase in PpIX as this may increase the risk of liver toxicity. Method: The patient had blood samples taken regularly for analyses of PpIX, znPpIX, ALT, ALP, iron, leucocytes, C-reactive protein, and hemoglobin before, during, and after treatment with teriflunomide. Additionally, we tested if teriflunomide increased PpIX in vitro. Results: A female EPP patient was treated for 7 years with teriflunomide for multiple sclerosis attacks. During treatment, her natural PpIX level increased from about 30 µmol/L to about 200 µmol/L, without significant simultaneous changes in hemoglobin, iron levels, alanine transaminase (ALT), or alkaline phosphatase (ALP). The patient experienced no increase in photosensitivity. In vitro addition of teriflunomide did not affect PpIX levels. Discussion: In patients with lead intoxication, the release of PpIX from erythrocytes is very slow. The increase in PpIX during treatment with teriflunomide compared to periods with no medication could be caused by a similar slow PpIX release from the erythrocytes. This theory is supported by the patient’s unchanged light sensitivity and stable levels of hemoglobin, iron, and liver enzymes. Full article

This study investigates the psychological and emotional mechanisms underlying women’s reactions to breast cancer awareness advertisements through the dual lens of Protection Motivation Theory (PMT) and neuromarketing methods, addressing a gap in empirical research on the integration of biometric and cognitive approaches in health marketing. Utilizing a lab-based experiment with 78 women aged 40 and older, we integrated Facial Expression Analysis using Noldus FaceReader 9.0 with semi-structured post-exposure interviews. Six manipulated health messages were embedded within a 15 min audiovisual sequence, with each message displayed for 5 s. Quantitative analysis revealed that Ads 2 and 5 elicited the highest mean fear scores (0.45 and 0.42) and surprise scores (0.35 and 0.33), while Ad 4 generated the highest happiness score (0.31) linked to coping appraisal. Emotional expressions—including fear, sadness, surprise, and neutrality—were recorded in real time and analyzed quantitatively. The facial analysis data were triangulated with thematic insights from interviews, targeting perceptions of threat severity, vulnerability, response efficacy, and self-efficacy. The findings confirm that fear-based appeals are only effective when paired with actionable coping strategies, providing empirical support for PMT’s dual-process model. By applying mixed-methods analysis to the evaluation of health messages, this study makes three contributions: (1) it extends PMT by validating the emotional–cognitive integration framework through biometric–qualitative convergence; (2) it offers practical sequencing principles for combining threat and coping cues; and (3) it proposes cross-modal methodology guidelines for future health campaigns. Full article

This paper aims to analyze adults’ responses to children’s argumentative contributions within children–adult dialogic interactions. More precisely, we focus on the phenomenon of children opening subdiscussions within argumentative interactions with peers and adults. This phenomenon occurs when a child problematizes and calls into question some proposition in the ongoing discussion, hence the opening of a subdiscussion is an initiative that comes as unexpected from the perspective of the adult. In this contribution, we examine what happens after a child opens a subdiscussion and how the adult’s reaction to such initiatives can shape the development of dialogue. This means that we observe adult behaviour in dialogic interactions with children, given the complexity of the adult’s role in such interactions. Drawing on the dialogical approach to argumentation, we present and discuss some excerpts of children–adult subdiscussions at a kindergarten. The data analysis uses concepts and tools from a linguistics-based approach to argumentation, i.e., the pragma-dialectical theory, and it highlights conversational dynamics of children–adult argumentative discourse. The study’s contribution is twofold: (1) it presents the important and delicate role of the adult in dialogic children–adult interactions; (2) it shows how the development of children’s arguments is intrinsically linked to the flexibility of the discussion space organized by the adult. Full article