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Continuous advancement in molecular electronics demands increasing functionality and diversity of integrated molecular junctions; however, single-functional molecular junctions fail to meet these requirements. In this article, we propose the use of a widely applicable and efficient click reaction on the surface to modify self-assembled monolayers (SAMs) to achieve multifunctional molecular tunnelling junctions, current rectification and memristance, on a single chip. This approach has allowed us to meet the growing demand for versatility and functionality in molecular electronic devices. [ABSTRACT FROM AUTHOR]

Recycling critical elements from spent batteries has always placed an emphasis on green chemistry. However, the reduction or minimization of the input of chemicals, secondary waste and energy consumption still needs to explore new technologies. In this work, we propose a paired electrolysis process to concurrently treat lithium cobalt oxide (LiCoO2, as a cathode) and lithium iron phosphorate (LiFePO4, as an anode) in sulfuric acid solution. In this process, LiCoO2 is reduced to release Co2+ and Li+ into the electrolyte through a surface chemical reaction control process. The activation energies of Li and Co are 23.38 and 28.70 kJ mol−1. LiFePO4 is oxidized to FePO4 while releasing Li+ through a surface chemical reaction control process with an activation energy of 14.95 kJ mol−1. Through this approach, both leaching efficiencies of Li and Co reach above 98%. Since two electrode reactions simultaneously proceed in one electrolytic cell, the paired electrolysis has the benefit of maximizing energy efficiency, as well as reducing the amount of chemicals and secondary waste. [ABSTRACT FROM AUTHOR]

[Display omitted] Developing cost-effective cocatalyst-modified photocatalytic systems with boosted carrier separation and rapid surface catalytic reaction is an ideal strategy for effectively converting solar energy into desired fuels. Herein, a series of Cu 7 S 4 /Mn 0.3 Cd 0.7 S hierarchical heterostructures are designed and fabricated to achieve efficient and robust photocatalytic H 2 evolution by coupling one-dimensional (1D) Mn 0.3 Cd 0.7 S nanorods with two-dimensional (2D) Cu 7 S 4 nanosheets through a facile sonochemical strategy. Benefiting from dimensionality and cocatalyst effects, the constructed 2D/1D Cu 7 S 4 /Mn 0.3 Cd 0.7 S heterojunction photocatalyst containing 1.5 wt% Cu 7 S 4 displays excellent photostability and superior photocatalytic H 2 evolution rate up to 914.3 μmol h−1, which is 4.43 and 2.22-folds increment relative to bare Mn 0.3 Cd 0.7 S and the 3 wt% Pt/Mn 0.3 Cd 0.7 S, respectively. The various characterization results reveal that the utilization of semimetallic Cu 7 S 4 nanosheets as the cocatalyst to form a Schottky heterojunction can promote the light-harvesting capability, suppress charge carrier recombination, and provide sufficient reaction sites for hydrogen generation, thereby resulting in the dramatically improved photocatalytic performance. This work clarifies the role of Cu 7 S 4 nanosheets as the robust and cost-effective cocatalyst in the photocatalytic reaction and opens a new horizon for designing other Cu 7 S 4 -based cocatalyst/semiconductor Schottky heterostructures for efficient solar-to-fuel conversion. [ABSTRACT FROM AUTHOR]

Conversion of producer gas tar without coke generation is a great challenge. This study investigates conversion of tar model benzene using different configurations of highly non-porous ɣ-Al 2 O 3 packed bed reactor at 1000–1100 0C. The configurations comprised of different positions (relative to top (P 1), center (P 2) and bottom (P 3) of reactor furnace), heights (5, 13 and 25 cm) and particles sizes (0.5, 3 and 5 mm) of alumina packed bed. Steam and CO 2 were used as reforming media for tested benzene concentrations (0.4–1.8 vol%). The results showed benzene conversions of 48–91% with negligible steady thin coke generation using a packed bed (height: 25 cm, particles size: 3 mm) at P 1. Whereas, relative high benzene conversions of 63–93 and 68–95% at P 2 and P 3 respectively with unsteady thick coke generation at benzene concentrations greater than 0.4 vol% increased differential upstream pressures (DUPs) of beds. Similar unsteady coke generation at benzene concentrations greater than 0.8 vol% and temperature of 1100 0C was observed with packed beds of heights of 5 and 13 cm, and particles size of 0.5 mm at P 1. Generation of unsteady coke with condensed structure as evidenced by its characterization was attributable to increased benzene polymerization and reduced bed surface gasification reactions due to improperly installed packed bed. Developed kinetic model predicted well the generated coke. As conclusion, properly installed alumina packed bed pertaining to tar concentration and other experimental conditions may inhibit coke generation during tar conversion. • Packed bed position influenced both benzene conversion and observed coke generation. • Packed bed height and particles size influenced coke generation only. • Increased polymerization and reduced gasification reactions lead coke generation. • Reduced concentrations of steam other than of CO2 generated coke. • Developed kinetic model estimated the generated coke well. [ABSTRACT FROM AUTHOR]

Mixtures of ethanol and methanol being synthesized from CO2 and green H2 can serve as sustainable base chemicals for a number of chemical processes. Amongst these processes, the catalytically supported synthesis of CO2-neutral C4 to C10 alcohols is of increasing importance as, e.g., iso-butanol can be used as a drop-in fuel or after dehydration to produce iso-butene as a feedstock for the synthesis of plastics. 2-ethyl-hexanol can be further refined into solvents, tensides, or monomers. In this respect, NiPt alloys on an activated carbon support were found to be active and stable catalysts for the synthesis of iso-butanol following the Guerbet reaction scheme. In this study, two different routes are applied to the synthesis of these NiPt catalysts: a more conventional one based on the impregnation of Ni and Pt salts and an advanced path with a surface redox reaction between elemental Ni on the support and Pt ions in a polar solution. The experimental evaluation shows that the Pt particles from the surface redox reaction being exposed on the Ni particles are more active than those on the impregnated catalysts due to their high surface energy. Their specific space-time yields are 10–20 times higher. [ABSTRACT FROM AUTHOR]

The yttrium aluminium garnet (YAG) and sapphire materials are commonly used in laser and optical devices. Producing an ultra-precise surface quality is necessary for the application in optical devices. However, YAG and sapphire materials belong to difficult-to-machine materials with high brittleness and hardness. Therefore, ensuring the main criterion of producing a quality surface in the nanometre form with the ability to remove the material when finishing this material is challenging. Eliminating machining residues using chemical–mechanical slurry (CMS) is essential in creating ultra-precise components in optical devices. Based on this feature, this work investigates the efficiency of the CMS polishing process by comparing the surface reaction modes with the ionic and solid reaction modes when polishing YAG and sapphire materials. The study procedures aim to clarify the polishing performance corresponding to these two reaction types. Experimental analyses show the balance between CMS polishing technology's mechanical and chemical effects with the ionic reaction model that can be generated. Results also show that the ionic surface reaction modes give more uniform material removal than the solid reaction on YAG and sapphire crystal surfaces. Therefore, when polished by CMS technology with ionic surface reaction modes, the surface quality is better than solid reaction. In the CMS polishing with ionic responses, adding more Na 2 SiO 3 –5H 2 O content to the CMS is necessary if the chemical reaction is weak. This process will facilitate the –Si–OH components to be more distributed on the workpiece's surface, thereby improving reaction speed and correcting the balance between mechanical and chemical in polishing by CMS. This balance action results in an ultra-smooth YAG crystal surface without scratches, with a roughness obtained in the nanometre form (Ra = 1.031 nm) after polishing by CMS-2. [ABSTRACT FROM AUTHOR]

Black ginseng (BG) is processed ginseng traditionally made in Korea via the steaming and drying of ginseng root through three or more cycles, leading to changes in its appearance due to the Maillard reaction on its surface, resulting in a dark coloration. In this study, we explored markers for differentiating processed ginseng by analyzing the chemical characteristics of BG. We elucidated a new method for the structural identification of ginsenoside metabolites and described the features of processed ginseng using UPLC-QTOF-MS in the positive ion mode. We confirmed that maltose, glucose, and fructose, along with L-arginine, L-histidine, and L-lysine, were the key compounds responsible for the changes in the external quality of BG. These compounds can serve as important metabolic markers for distinguishing BG from conventionally processed ginseng. The major characteristics of white ginseng, red ginseng, and BG can be distinguished based on their high-polarity and low-polarity ginsenosides, and a precise method for the structural elucidation of ginsenosides in the positive ion mode is presented. [ABSTRACT FROM AUTHOR]

Lattice models are a useful tool to simulate the kinetics of surface reactions. Since it is expensive to propagate the probabilities of the entire lattice configurations, it is practical to consider the occupation probabilities of a typical site or a cluster of sites instead. This amounts to a moment closure approximation of the chemical master equation. Unfortunately, simple closures, such as the mean-field and the pair approximation (PA), exhibit weaknesses in systems with significant long-range correlation. In this paper, we show that machine learning (ML) can be used to construct accurate moment closures in chemical kinetics using the lattice Lotka–Volterra model as a model system. We trained feedforward neural networks on kinetic Monte Carlo (KMC) results at select values of rate constants and initial conditions. Given the same level of input as PA, the ML moment closure (MLMC) gave accurate predictions of the instantaneous three-site occupation probabilities. Solving the kinetic equations in conjunction with MLMC gave drastic improvements in the simulated dynamics and descriptions of the dynamical regimes throughout the parameter space. In this way, MLMC is a promising tool to interpolate KMC simulations or construct pretrained closures that would enable researchers to extract useful insight at a fraction of the computational cost. [ABSTRACT FROM AUTHOR]

In this study, Au nanoparticle decorated Ni2P nanosheet arrays (Au/Ni2P) with a porous grid are synthesized using hydrothermal and electrodeposition reactions for the first time. The Au/Ni2P nanosheet arrays can electrocatalytically oxidize hydroquinone to produce a current for the detection of hydroquinone. A hydroquinone sensor is fabricated by Au/Ni2P with a porous grid, which can take full advantage of the synergistic catalysis of Au nanoparticles and Ni2P. The catalytic reaction sites of hydroquinone and the potential energy surface of the reaction pathway were predicted by Gaussian 09 and Multiwfn. Prominent performance was recorded for the hydroquinone sensor, attaining a wide linear range from 0.5 to 4000 μM, an excellent sensitivity of 1715 μA mM−1 cm−2, a low detection limit of 0.26 μM, as well as reliable selectivity, repeatability and stability. Gratifyingly, the sensor could satisfy the requirements of hydroquinone determination in actual environmental water, such as in tap water and rainwater. [ABSTRACT FROM AUTHOR]

We develop a continuum framework applicable to solid-state hydrogen storage, cell biology and other scenarios where the diffusion of a single constituent within a bulk region is coupled via adsorption/desorption to reactions and diffusion on the boundary of the region. We formulate content balances for all relevant constituents and develop thermodynamically consistent constitutive equations. The latter encompass two classes of kinetics for adsorption/desorption and chemical reactions—fast and Marcelin–De Donder, and the second class includes mass action kinetics as a special case. We apply the framework to derive a system consisting of the standard diffusion equation in bulk and FitzHugh–Nagumo type surface reaction–diffusion system of equations on the boundary. We also study the linear stability of a homogeneous steady state in a spherical region and establish sufficient conditions for the occurrence of instabilities driven by surface diffusion. These findings are verified through numerical simulations which reveal that instabilities driven by diffusion lead to the emergence of steady-state spatial patterns from random initial conditions and that bulk diffusion can suppress spatial patterns, in which case temporal oscillations can ensue. We include an extension of our framework that accounts for mechanochemical coupling when the bulk region is occupied by a deformable solid. This article is part of the theme issue 'Foundational issues, analysis and geometry in continuum mechanics'. [ABSTRACT FROM AUTHOR]

Porous or hollow crystals have attracted considerable interest due to their unique properties and outstanding performance in various applications. In this study, hollow Pb1−xSrxF2 crystals have been successfully fabricated via controlled precipitation–dissolution at the liquid–gas interface. As a result of the reaction on the surface of a solution mixture of Pb(CH3COO)2 and Sr(CH3COO)2 under the action of gaseous HF, a film of Pb1−xSrxF2 crystals with a fluorite-type structure was formed. Placing the film on the water surface resulted in selective dissolution and formation of hollow crystals, associated with a relative increase in the overall Sr content in the Pb1−xSrxF2 solid solution. By adjusting the crystallization conditions and the dissolution time it was possible to obtain hollow crystals with a wall thickness of 20–40 nm, membrane films with ordered through holes, or microstructures with flower-like morphology. The Gas–Solution Interface Technique used in this work can potentially be utilized to synthesize other metal fluorides with tunable porous morphology. [ABSTRACT FROM AUTHOR]

The features of hydrogen trapping under the irradiation of zirconium alloys E110 and E635 with an electron beam (400 eV, 0.8 mA/cm2) in various gaseous ambient containing oxygen and hydrogen (Ar + O2 + H2; Ar + H2O) are studied. The effect of surface temperature on the hydrogenation of zirconium alloys under electron irradiation is studied. It is shown that neither exposure nor electron irradiation in a gaseous ambient containing a mixture of H2 and O2 at 700 K for 20 h leads to a change in the hydrogen level in the E110 alloy, while hydrogen partially escapes from the E635 alloy during the experiment. The amount of hydrogen in zirconium alloys after exposure in a gaseous ambient containing H2O in a similar temperature–time regime also changes insignificantly; however, if the alloys are irradiated with electrons under these conditions, then they contain 1.5–2 times more hydrogen. When temperature of the samples is raised to 900 K, electron irradiation in the presence of water vapor, on the contrary, reduces the trapping of hydrogen in the E110 and E635 alloys, compared with exposure in the same gaseous ambient without irradiation. It is concluded that electron irradiation affects the balance of surface reactions of formation of hydroxyl groups from adsorbed water molecules and reverse reactions of formation of water molecules from surface hydroxyls. The direction of shifting the balance of these reactions depends on the surface temperature. [ABSTRACT FROM AUTHOR]

The treatment of beryllium wastewater has become a major problem in industry. In this paper, CaCO3 is creatively proposed to treat beryllium-containing wastewater. Calcite was modified by an omnidirectional planetary ball mill by a mechanical−chemical method. The results show that the maximum adsorption capacity of CaCO3 for beryllium is up to 45 mg/g. The optimum treatment conditions were pH = 7 and the amount of adsorbent was 1 g/L, and the best removal rate was 99%. The concentration of beryllium in the CaCO3-treated solution is less than 5 μg/L, which meets the international emission standard. The results show that the surface co-precipitation reaction between CaCO3 and Be (II) mainly occurs. Two different precipitates are generated on the used-CaCO3 surface; one is the tightly connected Be (OH)2 precipitation, and the other is the loose Be2(OH)2CO3 precipitation. When the pH of the solution exceeds 5.5, Be2+ in the solution is first precipitated by Be (OH)2. After CaCO3 is added, CO32- will further react with Be3(OH)33+ to form Be2(OH)2CO3 precipitation. CaCO3 can be considered as an adsorbent with great potential to remove beryllium from industrial wastewater. [ABSTRACT FROM AUTHOR]

Photocatalytic hydrogen evolution coupled with organic oxidation reaction is a promising alternative to water splitting, where the efficiency is limited due to the weak correlation between charge separation and surface redox reactions. Here, employing nickel phthalocyanine (NiPc) for hole extraction, NiPc‐modified carbon dots (CDs) are combined with Cu–In–Zn–S quantum dots (CIZS QDs) toward a profound understanding of electron/hole extraction and surface proton generation and reduction. The optimal hydrogen evolution rate reaches 4.10 mmol g−1 h−1 for CIZS/NiPc–CDs with l‐ascorbic acid for hole consumption, 8.10 times to that of CIZS QDs, which is further promoted to 11.12 mmol g−1 h−1 under electron/hole coextraction with Ni2+ introduction. For benzyl‐alcohol‐oxidation‐coupled H2 evolution, this strategy shows a more dramatic activity enhancement (19.54 times), which is also appliable to methanol‐ or furfuryl‐alcohol‐oxidation coupling systems with state‐of‐the‐art activities. Transient photovoltage spectroscopy and apparent kinetics analysis indicate, for the first time, a light‐induced electrocatalysis effect consistent with the Volmer–Heyrovsky process, which establishes a quasiquantitative basis for balancing charge extraction and surface reactions. [ABSTRACT FROM AUTHOR]

[Display omitted] • 1T/2H-MoS 2 is first employed in the field of photo-thermal synergistic catalytic CO 2 reduction. • The CO production rate over 1T/2H-MoS 2 is 3.5 and 2.8 times higher than that of 1T-MoS 2 and 2H-MoS 2. • In situ DRIFTS investigate the involved intermediates and confirm that COOH* is crucial in the conversion of CO 2 to CO. Photocatalytic CO 2 reduction technology has been proposed as a promising solution to the greenhouse effect and energy crisis. However, the lower quantum efficiency limits its practical applications. Here, we have significantly improved the photocatalytic CO 2 reduction performance of MoS 2 by coupling the heterophase junction (1T/2H-MoS 2) construction and photo-thermal synergy strategies. At 200 °C and 42 mW·cm−2 of 420 nm LED irradiation, the CO production rate of 1T/2H-MoS 2 reached 35.3 μmol·g−1·h−1, which was 3.5 and 2.8 times that of 1T-MoS 2 and 2H-MoS 2 , respectively. In addition, only faint CO was detected under sole photo- or sole thermal catalysis conditions. Mechanism studies showed that COOH* was the key intermediate in the photo-thermal synergistic catalytic CO 2 reduction over 1T/2H-MoS 2. The heterophase junction engineering significantly facilitated the separation of photogenerated carriers, and the introduction of heat accelerated the charge migration and surface reaction rates. Our work provides innovative insights into the catalyst design and mechanism studies for photo-thermal synergistic catalytic CO 2 reduction. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pd@PdO/γ-Fe 2 O 3 @GC composite was synthesized by two-step wet-chemical strategy. • The resultant composite offered fast response (21 s) and swift recovery (29 s) times. • It delivered the highest gas response of 96.2 ± 1.5. • The ultra-low detection limit of 100 ppb was detected. With the current upsurge in hydrogen economies all over the world, an increased demand for improved chemiresistive H 2 sensors that are highly responsive and fast acting when exposed to gases is expected. Owing to safety concerns about explosive and highly flammable H 2 gas, it is important to develop resistive sensors that can detect the leakage of H 2 gas swiftly and selectively. Currently, interest in metal-organic frameworks (MOFs) for gas-sensor applications is increasing due to their open-metal sites, large surface area, and unique surface morphologies. In this research, a highly selective and sensitive H 2 -sensor was established based on graphitic carbon (GC) anchored spherical Pd@PdO core-shells over γ-Fe 2 O 3 microcube (Pd@PdO/γ-Fe 2 O 3 @GC which is termed as S3) heterostructure materials. The combined solvothermal followed by controlled calcination-assisted S3 exhibited a specific morphology with the highest surface area of 79.12 m2 g−1, resulting in fast response and recovery times (21 and 29 s, respectively), and excellent sensing performance (Δ R / R 0 ∼ 96.2 ± 1.5), outstanding long-term stability, and a 100 ppb detection limit when detecting H 2 -gas at room temperature (mainly in very humid surroundings). This result proves that adsorption sites provided by S3 can promote surface reactions (adsorption and desorption) for ultrasensitive and selective H 2 gas sensors. [ABSTRACT FROM AUTHOR]

Symmetric solid oxide electrolysis cells (SSOECs) have attracted considerable interest because of their low fabrication cost and few compatibility issues. However, the development of SSOECs is restricted by the lack of electrode materials with desirable catalytic activity and stability. Herein, novel double-perovskite Sr 2 Ti 1−x FeNi x O 6 (STFNx) oxides are prepared and evaluated as electrodes for CO 2 electrolysis in SSOECs. The Sr 2 Ti 0.9 FeNi 0.1 O 6 (STFNi01) electrode shows the best performance with the minimum polarization resistance. The physicochemical characterization reveals that Ni substitution increases the concentrations of surface-adsorbed oxygen species and electrical conductivity and enhances CO 2 chemical adsorption, improving the electrode surface reaction kinetics, as evidenced by the distribution of relaxation time analysis. The STFNi01 symmetric cell presents a current density of 0.91 A cm−2 at 1.6 V and 800 °C and shows no performance degradation in the durability test due to the excellent carbon deposition resistance, indicating that STFNi01 is a promising electrode material for SSOECs. [ABSTRACT FROM AUTHOR]

Controlling site-selectivity and reactivity in chemical reactions continues to be a key challenge in modern synthetic chemistry. Here, we demonstrate the discovery of site-selective chemical reactions on the water surface via a sequential assembly approach. A negatively charged surfactant monolayer on the water surface guides the electrostatically driven, epitaxial, and aligned assembly of reagent amino-substituted porphyrin molecules, resulting in a well-defined J-aggregated structure. This constrained geometry of the porphyrin molecules prompts the subsequent directional alignment of the perylenetetracarboxylic dianhydride reagent, enabling the selective formation of a one-sided imide bond between porphyrin and reagent. Surface-specific in-situ spectroscopies reveal the underlying mechanism of the dynamic interface that promotes multilayer growth of the site-selective imide product. The site-selective reaction on the water surface is further demonstrated by three reversible and irreversible chemical reactions, such as imide-, imine-, and 1, 3-diazole (imidazole)- bonds involving porphyrin molecules. This unique sequential assembly approach enables site-selective chemical reactions that can bring on-water surface synthesis to the forefront of modern organic chemistry. Controlling site-selectivity and reactivity in chemical reactions continues to be a key challenge in modern synthetic chemistry. Here, the authors demonstrate the assembly of amino-substituted porphyrins on a water surface into J-aggregate structures in the presence of charged surfactants. [ABSTRACT FROM AUTHOR]

In this work, the reaction pathways of one-step glycerol hydrodeoxygenation in the gas phase are exploited under flow conditions over molybdena-based catalysts (8.7 wt% Mo/black carbon). Hydrodeoxygenation (HDO) experiments with possible reaction intermediates along with temperature-programmed surface reaction spectroscopy (TPSR) experiments demonstrated two possible reaction pathways. The major one involves propylene formation via hydrodeoxygenation of 2-propen-1-ol which is considered to be the main intermediate of the reaction. In the secondary route, propanal formed via 2-propen-1-ol isomerization is further converted to 1-propanol. XPS measurements in fresh-reduced and reduced-used catalysts revealed that molybdena exists as multivalent species mostly as Mo5+, Mo4+ and Mo3+, the presence of which seems to be crucial for the desired pathway of successive HDOs towards propylene. TPSR tests using methanol as the probe molecule showed that redox and acid sites co-exist on the surface of reduced molybdena catalysts, and this bifunctionality is mostly served by the undercoordinated molybdena species. The long-term catalyst test at 280 °C and 60 bar pressure under glycerol hydrodeoxygenation conditions demonstrated that the catalyst remains stable in terms of activity and selectivity for the first 10 h with a gradual drop afterwards. Regeneration of the catalyst for a short time under hydrogen flow proved to be sufficient to fully recover the initial activity and product selectivity. [ABSTRACT FROM AUTHOR]

The depletion of groundwater resources in the water-stressed regions has led to the overuse of surface water reservoirs. Recharging groundwater by rejuvenating dried surface reservoirs using recycled water is a new sustainable solution. To ensure the prevention of groundwater contamination and associated health risks (as recycled water is used), it is crucial to assess the surface reservoir water quality. The study for the first time suggests the Lake2K model, a one-dimensional mechanistic mass-balance model, to simulate the changes in water quality in a series of man-made surface water reservoirs where recycled water flows under an indirect groundwater recharge scheme (soil aquifer treatment system). The model was developed, calibrated, and validated using field observations to estimate degradation/reaction rate constants for various water quality parameters. The observed average degradation/reaction rate constants for parameters including ammonia-N, nitrate–N, total nitrogen, total organic carbon, and organic phosphorous were 0.043 day−1, 0.04 day−1, 0.043 day−1, 0.055 day−1, and 0.056 day−1, respectively, which were found to be relatively high compared to existing literature, indicating a greater degradation of these parameters in warmer climates. The results showed that the water quality improved significantly as the water progressed through the reservoirs, aligning with field observations. Additionally, the simulated seasonal variations revealed that the maximum growth rate of phytoplankton occurred during July, August, and September for each reservoir, while the nutrient pool (nitrate–N and orthophosphates) experienced the greatest depletion during this growth period. These findings shed light on the dynamics of surface water quality in regions facing water scarcity and contribute to the development of sustainable groundwater management strategies. [ABSTRACT FROM AUTHOR]

In this work, the influences of polymers (HPMC E3, PEG 6000, PVP K25, PVP K30), temperature, stirring speed and polymer mass fraction on the oxaprozin (OXA) dissolution profiles were measured by a United States Pharmacopeia (USP) Ⅱ dissolution apparatus. The two-step chemical potential gradient model combined with the interfacial steady-state mass transfer model as well as PC-SAFT (perturbed-chain statistical associating fluid theory) were used to analyze the dissolution mechanism of OXA under different conditions. The presence of polymer could promote the surface reaction of OXA while temperature and stirring speed have different influences on the surface reaction and diffusion. The diffusion boundary layer thickness δ of OXA tablets increases with the increase of temperature and decreases with the increase of stirring speed. Based on the obtained surface reaction rate constant k s and diffusion rate constant k d , the dissolution profiles with high accuracy compared with the experimental data. [Display omitted] • Calculating the concentration at solid-liquid interface by mass transfer model. • The presence of excipients affects the solubility and dissolution mechanism. • Temperature and stirring speed affect the dissolution mechanism. • Surface reaction and diffusion work together to control dissolution. [ABSTRACT FROM AUTHOR]

Struvite (MgNH 4 PO 4 ·6 H 2 O，MAP), a type of high-quality, slow-release fertilizer, is the main component of urinary stones in animals and humans and causes scale formation in industrial pipes. Therefore, MAP dissolution is an important research topic. Herein, MAP dissolution experiments are performed and a thermodynamic model is developed to evaluate the influences of pH, temperature (T), and particle size (P s) on surface reaction resistance (1/k s) and diffusion resistance (1/k d). The results show that MAP solubility decreases with an increase in pH and the effects of pH change are more obvious than those of T or P s. The total resistance (1/k T) of MAP dissolution increases with pH increase, P s growth, or T reduction. The comparison of 1/k s and 1/k d reveals surface reaction as the MAP dissolution control step and indicates a linear relation among 1/k s , 1/k d , and the natural logarithm of P s at pH 7.0. [Display omitted] • The solubility of struvite is more affected by pH than temperature and particle size. • The resistances during the dissolution process of struvite were calculated. • Surface reaction is the controlling step in the dissolution of struvite. • The resistance was found to have a linear relationship with particle size at pH 7. [ABSTRACT FROM AUTHOR]

This paper describes a study of the ignition and combustion characteristics of a high-energy material containing ammonium perchlorate, butadiene rubber, and an ultrafine powder mixture of aluminum, titanium, or iron with amorphous boron. An experimental stand based on a CO2 laser and a constant-pressure bomb is used to measure the ignition delay time and burning rate of the high-energy material while varying the heat flux density and the chamber pressure. It is shown that replacing amorphous boron with ultrafine Al/B, Ti/B, or Fe/B in a high-energy material reduces the heating time and the moment at which a flame appears on the propellant surface due to an increase in the reaction rate and a decrease in the oxidation temperature of these mixtures on the surface of the reaction layer. In this case, the burning rate of the high-energy materials with Me/B at excess pressures increases significantly (up to 240% for Al/B-HEM and up to 120% for Ti/B-HEM at a pressure of 5.0 MPa). [ABSTRACT FROM AUTHOR]

In order to provide atomistic details for the mechanism of the collisional dynamics of O(3P) and dimethylamine (DMA) in the triplet electronic surface, direct dynamics simulations are reported herein. The simulations are performed at the U‐HSE06/aug‐cc‐pVDZ level of theory. The results are reported for the relative collision energy of 7.8 kcal/mol. For the vibrational and rotational excitations, following temperature regimes have been considered: 200 and 10 K, respectively. Simulations reveal that the reaction can lead to two product channels in the considered energy regime: (1) 2OH + 2CH3NHCH2 and (2) 2OH + 2CH3NCH3. The computed reaction cross section for pathways 1 and 2 are as follows: 17.89 ± 0.20 Å2 and 3.28 ± 0.03 Å2, whereas the computed microcanonical reaction rate constants for pathways 1 and 2 are as follows: (4.21 ± 0.05)*10−10 and (7.72 ± 0.07)*10−11 cm3/(molecule sec). Both pathways follow direct and indirect H abstraction processes. Among the direct pathways, stripping and rebound mechanisms have been observed, whereas the indirect pathway involves formation of a post‐reaction complex having lifetime ~0.4–0.5 ps. The velocity scattering angle distribution for the reaction is dominated by scattering in the sideways (60–120 °) and backward (120–180 °) directions with some contribution from the scattering in the forward direction (0–60 °). [ABSTRACT FROM AUTHOR]

In the field of catalysis, dry reforming, that is, methane reforming with CO2$\rm {CO_2}$, is in the focus due to growing environmental concerns about oil depletion and global warming with a desire to produce synthesis gas. However, this process can lead to the formation of carbon, which can cause catalyst deactivation, especially at industrial conditions. Nevertheless, the key to develop a more coke‐resistant catalyst is a better comprehension of the reforming process at a molecular level. Regardless of all the investigations available in literature, the detailed path for the conversion of methane to syngas and carbon remains a controversial issue. Another problem in setting up a reaction mechanism is the difficulty to define the thermodynamic data for intermediate surface species and this leads to the development of thermodynamic consistent surface reaction mechanisms in literature where the thermodynamic data are not used to calculate the rate coefficients of the reverse reactions. Rather the Arrhenius parameters for the forward as well as backward reactions are explicitly given in the reaction mechanism to establish thermodynamic equilibrium. In this investigation, a kinetically consistent detailed surface reaction mechanism is developed which consists of 26 reversible reactions with the help of a one‐dimensional model, LOGEcat. Our previous work constructs the basis of the present investigation. Further, a detailed sensitivity analysis of reversible reactions and reaction pathways is performed to understand the mechanism better. The mechanism is validated for dry reforming of methane over nickel catalyst, however, it can also be used for other processes, such as, steam reforming and partial oxidation. The mechanism is tested by comparing the simulation results with the literature experiments and simulations in a wide range of temperature. The new developed kinetically consistent surface reaction mechanism is able to accurately express the dry reforming of methane over the nickel catalyst for complete range of temperature and also provide a useful insight into the key rate determining steps. [ABSTRACT FROM AUTHOR]

Since photocatalytic reactions are surface reactions, enhancing gas movement around the photocatalyst could improve photocatalytic CO2 reduction performance. A new approach using black body material to enhance the gas movement around the photocatalyst based on the natural thermosiphon movement of gases around a photocatalyst has been proposed and confirmed experimentally, but the heat-transfer mechanism of the phenomena has not yet been clarified. The aim of this study is to clarify the corresponding heat-transfer mechanism. This study calculated the temperature of the CO2/NH3 gas mixture around a P4O10/TiO2 photocatalyst using the heat-transfer formula. No difference was found between the temperature increase (Tg) from the temperature at the beginning of the CO2 reduction experiment (Tini) and the temperature of the CO2/NH3 gas mixture measured experimentally via thermocouple (Te) under the following illumination conditions: a Xe lamp with visible light (VIS) + infrared light (IR) and IR only. The heat-transfer model proposed in this study predicts Tg well under illumination from a Xe lamp with VIS + IR as well as under IR illumination only. On the other hand, the difference found between Tg and Te was as large as 10 °C under illumination from a Xe lamp with ultraviolet light (UV) + VIS + IR. [ABSTRACT FROM AUTHOR]

The slow charge reactions at the semiconductor surface severely encumber the photocatalysis applications, which are elusive and complicated in a serial charge excitation-separation-reaction process. Both experimental and theoretical studies are essential in this area. Here, a classical numerical calculation of the charge reaction microkinetic is developed based on a simple consecutive charge separation and reaction model, a conservation law of photogenerated charges, and differential analysis. Several reaction conditions have been discussed to elucidate how a fast charge separation and reaction rate constant influence the apparent reaction kinetics. It is shown that a slower charge separation rate strongly limits the detection of higher-order reaction rates, and higher-order kinetics can be detected with all other processes faster than the reactions. This numerical calculation projects the possible limitations of kinetics study by transient techniques. [ABSTRACT FROM AUTHOR]

The acid–base surface properties of vivianite crystals highly affect the adsorption capacity of vivianite for heavy metals and organic matters in aqueous solution. Therefore, the aim of the study was to innovatively explore and quantify the acid–base surface characterization of vivianite crystals in aqueous solution. It was found that the two surface active adsorption sites (≡POH and ≡FeOH) and five surface species thereof (i.e., ≡PO, ≡POH, ≡FeOH, ≡FeO−, and ≡FeOH2+) underwent surface reaction on vivianite crystals. Moreover, the active surface site and point of zero charge of vivianite crystals were 18 sites/nm2 and pH 5.9. Importantly, constant capacitance model was successfully employed to model the titration data, from which the distribution of surface species as function of pH and surface reaction constants were also accurately derived. The finding herein can be applied for plausible modeling molecular‐scale adsorption of the impurities on vivianite surface. [ABSTRACT FROM AUTHOR]

A mathematical model is developed to analyze the free convection flow induced by catalytic surface reaction on a vertical wavy surface embedded in a non-Darcy porous medium. The governing equations are transformed using a generalized transformation which are valid near to and far from the leading edge. We then solve the resulting equations employing finite difference method. A comparison between the present solutions and the results of a past study is made which provides a good agreement. Numerical results reveal that the wall temperature and the surface concentration are enhanced for higher heat release parameter. An increase in the amplitude of the wavy surface and the reactant consumption parameter causes a decrease in the wall temperature and the surface concentration. Due to the increase of the reduced Darcy number the wall temperature substantially becomes higher whereas the surface concentration diminishes. However, a converse characteristic is observed in the case of the activation energy parameter. The momentum, thermal and concentration boundary layers are significantly increased for higher values of the reduced Darcy number and the consumption reactant parameter. Contrary to this, the larger heat release parameter reduces the thicknesses of the momentum, thermal and concentration boundary layers. [ABSTRACT FROM AUTHOR]

Dimethyl sulfide (DMS) is an important trace gas emitted from the ocean. The oxidation of DMS has long been recognised as being important for global climate through the role DMS plays in setting the sulfate aerosol background in the troposphere. However, the mechanisms in which DMS is oxidised are very complex and have proved elusive to accurately determine in spite of decades of research. As a result the representation of DMS oxidation in global chemistry–climate models is often greatly simplified. Recent field observations and laboratory and ab initio studies have prompted renewed efforts in understanding the DMS oxidation mechanism, with implications for constraining the uncertainty in the oxidation mechanism of DMS as incorporated in global chemistry–climate models. Here we build on recent evidence and develop a new DMS mechanism for inclusion in the UK Chemistry Aerosol (UKCA) chemistry–climate model. We compare our new mechanism (CS2-HPMTF) to a number of existing mechanisms used in UKCA (including the highly simplified three-reactions–two-species mechanism used in CMIP6 studies with the model) and to a range of recently developed mechanisms reported in the literature through a series of global and box model experiments. Global model runs with the new mechanism enable us to simulate the global distribution of hydroperoxylmethyl thioformate (HPMTF), which we calculate to have a burden of 2.6–26 Gg S (in good agreement with the literature range of 0.7–18 Gg S). We show that the sinks of HPMTF dominate uncertainty in the budget, not the rate of the isomerisation reaction forming it and that, based on the observed DMS / HPMTF ratio from the global surveys during the NASA Atmospheric Tomography mission (ATom), rapid cloud uptake of HPMTF worsens the model–observation comparison. Our box model experiments highlight that there is significant variance in simulated secondary oxidation products from DMS across mechanisms used in the literature, with significant divergence in the sensitivity of the rates of formation of these products to temperature exhibited; especially for methane sulfonic acid (MSA). Our global model studies show that our updated DMS scheme performs better than the current scheme used in UKCA when compared against a suite of surface and aircraft observations. However, sensitivity studies underscore the need for further laboratory and observational constraints. In particular our results suggest that as a priority long-term DMS observations be made to better constrain the highly uncertain inputs into the system and that laboratory studies be performed that address (1) the uptake of HPMTF onto aerosol surfaces and the products of this reaction and (2) the kinetics and products of the following reactions: CH 3 SO 3 decomposition, CH 3 S + O 2 , CH 3 SOO decomposition, and CH 3 SO + O 3. [ABSTRACT FROM AUTHOR]

Hafnium oxide (HfO2) is widely recognized as one of the most promising high-k dielectric materials due to its remarkable properties such as high permittivity, wide band gap, and excellent thermal and chemical stability. The atomic layer deposition (ALD) of HfO2 has attracted significant attention in recent decades since it enables uniform and conformal deposition of HfO2 thin films on various substrates. In this study, we examined the initial surface reactions of a series of homoleptic hafnium precursors on hydroxylated Si(100) surfaces using density functional theory calculations. Our theoretical findings align with previous experimental studies, indicating that hafnium amides exhibit higher reactivity compared to other precursors such as hafnium alkoxides and hafnium halides in surface reactions. Interestingly, we found that the chemisorption and reactivity of hafnium precursors are considerably affected by their thermal stability and size. For alkoxide precursors, which have similar thermal stabilities, the size of alkoxide ligands is an important factor in determining their reactivity. Conversely, the reactivity of hafnium halides, which have ligands of similar sizes, is primarily governed by their thermal stability. These insights are valuable for understanding the surface reaction mechanisms of precursors on hydroxylated Si(100) surfaces and for designing new materials, particularly heteroleptic precursors, in future research. [ABSTRACT FROM AUTHOR]

Phenolic compounds are ubiquitous in nature because of their unique physical and chemical properties and wide applications, which have received extensive research attention. Phenolic compounds represented by tannic acid (TA) play an important role at the nanoscale. TA with a polyphenol hydroxyl structure can chemically react with organic or inorganic materials, among which metal–phenolic networks (MPNs) formed by coordination with metal ions and polyphenol derivatives formed by interactions with organic matter, exhibit specific properties and functions, and play key roles in photo(electro)catalysis. In this paper, we first introduce the fundamental properties of TA, then summarize the factors influencing the properties of MPNs and structural transformation of polyphenol-derived materials. Subsequently, the functions of MPNs and polyphenol derivatives in photo(electro)catalysis reactions are summarized, encompassing improving interfacial charge carrier separation, accelerating surface reaction kinetics, and enhancing light absorption. Finally, this article provides a comprehensive overview of the challenges and outlook associated with MPNs. Additionally, it presents novel insights into their stability, mechanistic analysis, synthesis, and applications in photo(electro)catalysis. [ABSTRACT FROM AUTHOR]

The traditional method of monitoring the oxidation and reduction of biomedical materials usually relies on electrochemical (EC) measurement techniques. Here, we demonstrate a surface plasmon resonance (SPR) method to monitor the oxidation process. Using levodopa L-dopa as the target analyte, a nanohole sensing plate is embedded in the EC electrode to enhance the oxidation signal and generate SPR. Cyclic voltammetry (CV) measurement was first conducted to understand the baseline of EC response of L-Dopa. Then, the redox reactions were simultaneously monitored through SPR measurements during the CV voltage scan. The results showed that the limit of detection using traditional CV reached 1.47 μM while using EC-SPR, the limit of detection improved to 1.23 μM. Most importantly, we found a strong correlation between CV current profiles and the SPR reflection spectra. Our results facilitate detecting electrochemical reactions using an optical probing method. [ABSTRACT FROM AUTHOR]

We describe here a new process for the synthesis of very high quality 2D Covalent Organic Frameworks (COFs), such a C2N and CN carbon nitrides. This process relies on the use of a metallic surface as both a reagent and a support for the coupling of small halogenated building blocks. The conditions of the assembly reaction are chosen so as to leave the inorganic salts by-products on the surface, to further confine the assembly reaction on the surface and increase the quality of the 2D layers. We found that under these conditions, the process directly returns few layers material. The structure/quality of these materials is demonstrated by extensive cross-characterizations at different scales, combining optical microscopy, Scanning Electron Microscopy (SEM)/Transmission Electron Microscopy (TEM) and Energy Dispersive Spectroscopy (EDS). The availability of such very large, high-quality layers of these materials opens interesting perspectives, for example in photochemistry and electronics (intrinsic transport properties, high gap substrate for graphene, etc...). [ABSTRACT FROM AUTHOR]

We review the milestones in the century-long development of the theory of diffusion-controlled reactions. Starting from the seminal work by von Smoluchowski, who recognized the importance of diffusion in chemical reactions, we discuss perfect and imperfect surface reactions, their microscopic origins, and the underlying mathematical framework. Single-molecule reaction schemes, anomalous bulk diffusions, reversible binding/unbinding kinetics, and many other extensions are presented. An alternative encounter-based approach to diffusion-controlled reactions is introduced, with emphasis on its advantages and potential applications. Some open problems and future perspectives are outlined. [ABSTRACT FROM AUTHOR]

This study focuses on the dissolution process and surface characterization of amosite fibres following interaction with a mimicked Gamble's solution at a pH of 4.5 and T = 37 °C, up to 720 h. To achieve this, a multi-analytical approach was adopted, and the results were compared to those previously obtained on a sample of asbestos tremolite and UICC crocidolite, which were investigated under the same experimental conditions. Combining surface chemical data obtained by XPS with cation release quantified by ICP-OES, an incongruent behaviour of the fibre dissolution was highlighted for amosite fibres, similarly to asbestos tremolite and UICC crocidolite. In particular, a preferential release of Mg and Ca from the amphibole structure was observed, in agreement with their Madelung site energies. Notably, no Fe release from amosite fibres was detected in our experimental conditions (pH of 4.5 and atmospheric pO2), despite the occurrence of Fe(II) at the M(4) site of the amphibole structure, where cations are expected to be rapidly leached out during mineral dissolution. Moreover, the oxidation of both the Fe centres initially present on the fibre surface and those promoted from the bulk, because of the erosion of the outmost layers, was observed. Since biodurability (i.e., the resistance to dissolution) is one of the most important toxicity parameters, the knowledge of the surface alteration of asbestos possibly occurring in vivo may help to understand the mechanisms at the basis of its long-term toxicity. [ABSTRACT FROM AUTHOR]

In many engineering applications, it is important to consider the temperature dependence of a material's properties, such as its viscosity and thermal conductivity. Aiming the same, here, in the existing exploration, viscosity and thermal conductivity are taken as variables instead of constant. This study discusses the flow of a viscous fluid over a rotating disk with a surface catalyst. The homogeneous-heterogeneous reactions are supplemented by surface catalysis that boosts the chemical reaction rate in the minimum possible time. The novelty of the problem is enhanced by the incorporation of the variable diffusion coefficients of both chemical species. The Von Karman transformation is used and the system is scrutinized by the bvp4c function of the MATLAB software. The results are portrayed in the form of illustrations and tables. The outcomes divulged that the mass diffusion rate and wall concentration for the porosity and surface catalyzed parameter show a decreasing behavior. [ABSTRACT FROM AUTHOR]

The key function of lubricants is to reduce the friction, wear, and heat between the parts that are in contact with each other. The main applications of the lubricants are to control temperature, and reduction in wear and corrosion of the machinery. Keeping in mind the importance of lubrication and its applications in varied machines. The goal of this research is to inspect the heat transmission impact in the magnetohydrodynamic flow of Jeffrey liquid near a stagnation point through a lubricated surface. Lubrication is accomplished by a shear-thinning liquid. The velocity, continuity, and shear stress, amalgamated with power-law fluids, are used to develop interfacial conditions. The exclusivity of the anticipated model is the inclusion of variable thermal conductivity and diffusion coefficients in the existence of homogeneous-heterogeneous reactions. Using the Keller–Box finite-difference approximation approach, the numerical results are accomplished. The outcomes are portrayed and tabulated in the form of diagrams and tables, respectively. It is witnessed that a greater magnetic field affects the fluid flow velocity and the drag force coefficient. Moreover, it is also inferred that the heat transfer rate dwindled for the greater thermal conductivity parameter. Authentication of the presented model is also part of this investigation. [ABSTRACT FROM AUTHOR]

The photocatalytic hydrogen evolution performance of Co 3 O 4 @ZIS is significantly improved through the synergy of photothermal effect and heterojunction. [Display omitted] • Co 3 O 4 @ZnIn 2 S 4 core–shell heterojunction was constructed as a photothermal/ photocatalytic integrated system for photocatalytic hydrogen production. • The photothermal effect induced by Co 3 O 4 boosts the surface reaction kinetic of hydrogen evolution and ameliorates charge transfer. • Built-in electric field at Co 3 O 4 @ZnIn 2 S 4 heterojunction interface enhances charge separate and prolongs charge lifetimes. • Co 3 O 4 @ZnIn 2 S 4 shows much higher H 2 evolution activity than that of pure ZnIn 2 S 4. Integration of photothermal materials and photocatalysts can effectively improve photocatalytic hydrogen production. However, the synergistic mechanism of photothermal effect and heterojunction still need to be deeply investigated. Herein, Co 3 O 4 @ZnIn 2 S 4 (ZIS) core–shell heterojunction was constructed as a photothermal/ photocatalytic integrated system for photocatalytic hydrogen production. The photothermal effect induced by Co 3 O 4 boosts the surface reaction kinetic of hydrogen evolution with an apparent activation energy decrease from 42.0 kJ⋅mol−1 to 33.5 kJ⋅mol−1. The photothermal effect also increases the charge concentrations of Co 3 O 4 @ZIS, which ameliorates the conductivity of Co 3 O 4 @ZIS and thus benefits to charge transfer. In addition, a p-n junction forms between Co 3 O 4 and ZIS and provides a built-in electric field to enhance charge separate and prolong charge life time. Benefiting from the synergy of photothermal effect and heterojunction, the photocatalytic performance of Co 3 O 4 @ZIS is significantly improved with a highest hydrogen evolution rate of 4515 μmol⋅g−1⋅h−1, which is about 3.5 times higher than that of pure ZIS. This work offers a full perspective to understand the photothermal/photocatalytic integrated conception for solar hydrogen production. [ABSTRACT FROM AUTHOR]

The reaction between ozone and iodide is one of the main drivers of tropospheric ozone deposition to the ocean, due to the ubiquitous presence of iodide in the ocean surface and its rapid reaction with ozone. Despite the importance of this sea surface reaction for tropospheric ozone deposition, and also as the major source of atmospheric iodine, there is uncertainty in its rate and dependence on aqueous phase temperature. In this work, the kinetics of the heterogeneous second order reaction between ozone and iodide were investigated using conditions applicable to coupled ocean-atmosphere systems (1 × 10−7 – 1 × 10−5 M [iodide], 40 ppb ozone, 288 – 303 K, 15.0 psi). The Arrhenius parameters determined of A = 1.0 ± 4.6 ×1011 M−1 s−1 and Ea = 8.5 ± 10.9 kJ mol−1 show that the reaction has a negligible positive temperature dependence, which could be weakly negative within errors. This is in contrast to a previous study that found a strong positive activation energy and a pre-exponential factor many orders of magnitude greater than determined here. The re-measured kinetics of ozone and iodide were used to constrain a state-of-the-art sea surface microlayer (SML) model. The model replicated results from a previous laboratory study of the temperature dependence of hypoiodous acid (HOI) and molecular iodine (I2) emissions from an ozoneoxidised iodide solution. This work has significance for global modelling of dry deposition of ozone to the ocean and the subsequent emissions of iodine-containing species, thus improving understanding of the feedbacks between natural halogens, air quality, and climate change. [ABSTRACT FROM AUTHOR]

The purpose of this study was to carry out a material test to investigate the effect of different force plate coverings on vertical and horizontal ground reaction force and derived parameters. Four surface conditions were analysed; bare plate, vinyl, sportflex, and astroturf on a Kistler force plate. Vertical data were collected by dropping a 2 kg rigid, textured medicine ball from a low (61 cm) and a high (139 cm) height. Horizontal data were collected using a custom-built, rigid, metal pendulum device. A one-way ANOVA revealed a significant main effect of surface on peak force and rate of force development for high height, low height, and horizontal force conditions (all p<0.001), with effect sizes in the post-hoc analysis being mostly large to very large. Interestingly, sportflex yielded the highest vertical but the lowest horizontal ground reaction forces. This study showed the use of current force platform coverings had a significant effect on peak force and rate of force development measurements during a standardised testing procedure. Future research should try to obtain rate of force development values that more closely replicate aspects of human performance during standardised testing procedures. Also further investigate the effect of the different surfaces on ground reaction forces during human movement. [ABSTRACT FROM AUTHOR]

In this study, quasi-two-dimensional BixSn1−xO2 (BTO) thin films were fabricated using a liquid metal transfer method. The ultraviolet (UV) photodetector based on BTO thin films was constructed, and the ultrahigh responsivity of 589 A/W was observed at 300 nm UV light illumination. Interestingly, by dropping ethanol during light-off period, the recovery time induced by the persistent photoconductivity (PPC) effect is reduced from 1.65 × 103 s to 5.71 s. Furthermore, the recovery time can also be reduced by dropping methanol, propylene glycol, NaNO2, and Na2SO3 after light termination. The working mechanisms are attributed to the rapid consumption of holes stored in BTO thin films by reaction with those solutions. This work demonstrates that the BTO thin films have potential applications in high-performance UV detectors and present an innovation route to weaken the PPC effects in semiconductors by introducing chemical liquids on their surface. [ABSTRACT FROM AUTHOR]

The atomic scale solid–liquid interfacial process dominates the macro‐dissolution of silica, yet its direct experimental observation is challenging. Here we employed the reactive molecular dynamics to model this process in alkaline condition. An elevated temperature strategy under canonical ensemble (NVT) was applied to accelerate the process for sufficient sampling at temporal domain. A stepwise transformation from fully linked SiO4 network (Q3 and Q4) to reduced linkage and eventually aqueous species (Q0) was revealed. The simulated dissolution rate agrees well with the value predicted by empirical model. By tracing hydrogen atoms, we found that the dehydroxylated silica surfaces in alkaline electrolyte solutions underwent a transition from Si–O–Si bond cleavage‐dominated (mainly reacted with OH−) to hydroxylation‐dominated surface reactions. The free‐energy reconstruction of well‐tempered metadynamics reveals that 1500 K accelerates dissolution without altering the reaction pathways. These findings offer novel insights into the evolution of atomic‐scale surface configurations during the dissolution kinetics of silica. [ABSTRACT FROM AUTHOR]

A self-diffusiophoretic problem is considered for a chemically active dimer consisting of two equal touching spherical colloids that are exposed to different fixed-flux and fixed-rate surface reactions. A new analytic solution for the autophoretic mobility of such a catalytic Janus dimer is presented in the limit of a small Péclet number and linearization of the resulting Robin-type boundary value problem for the harmonic solute concentration. Explicit solutions in terms of the physical parameters are first obtained for the uncoupled electrostatic and hydrodynamic problems. The dimer mobility is then found by employing the reciprocal theorem depending on the surface slip velocity and on the normal component of the shear stress acting on the inert dimer. Special attention is given to the limiting case of a Janus dimer composed of an inert sphere and a chemically active sphere where the fixed-rate reaction (Damköhler number) is infinitely large. Examples are given, comparing the numerical and approximate analytic solutions of the newly developed theory. Singular points arising in the model are discussed for a dimer with a fixed-rate reaction, and the flow field around the dimer is also analysed. The new developed theory introduces a fast way to compute the mobility of a freely suspended dimer and the induced flow field around it, and thus can also serve as a sub grid scale model for a multi-scale flow simulation. [ABSTRACT FROM AUTHOR]

In this study, two materials based on reduced graphene oxide (rGOH or rGOE) were synthesized through the Hummers methodology and a more sustainable electrochemical method. These materials were extensively characterized and tested as catalysts in solketal production. Both rGOH and rGOE demonstrated significant catalytic activity, achieving 66.18% and 63.97% conversion rates, respectively. The catalytic activity of the synthesized materials was 30 times more efficient than the homogeneous catalyst p-Toluenesulfonic acid. Pseudo-homogeneous and heterogeneous kinetic models were employed to gain further insights into the glycerol ketalization reaction with acetone. The pseudo-homogeneous model suggested that the direct rate constant was lower than the reverse rate constant. In this sense, a reversible bimolecular reaction was proposed. The heterogeneous kinetic models revealed that in the Langmuir-Hinshelwood-Hougen-Watson mechanism, the controlling step of the reaction was the glycerol-acetone surface reaction on the catalyst. In contrast, in the Eley-Rideal mechanism, the reaction was controlled by the adsorbed glycerol on the reaction surface reacting with the available acetone in the bulk fluid. In the reusability tests, the rGOE catalyst demonstrated superior performance over five consecutive cycles, maintaining the highest activity without needing post-reaction washing or treatment. [ABSTRACT FROM AUTHOR]

Transition‐metal dichalcogenide (TMDC) islands and thin films are grown on TiO2(110) via physical vapor deposition of Mo and Se and are analyzed with electron diffraction, Auger spectroscopy, and scanning tunneling microscopy (STM). Surprisingly, large, crystalline TiSe2 patches develop on the TiO2 surface instead of the expected MoSe2 islands. They are identified by a hexagonal lattice with 3.4 Å periodicity, a unique (2 × 2) superstructure related to charge‐density waves, and an empty conductance doublet in STM spectroscopy. Density‐function‐theory calculations assign the imaging contrast and the conductance doublet to tunneling into the 3p orbitals of the topmost Se layer and Ti 3d‐related electronic states, respectively. Control experiments without Mo deposition confirm that the observed TMDC growth indeed results from a surface reaction between gas‐phase Se and Ti3+ atoms, segregating out of the reduced TiO2 crystal. From the unique shape and orientation of the TiSe2 islands in the low‐coverage regime, a distinct nucleation scheme is proposed, in which the Se(3 × 1) superstructure on TiO2 provides pinning centers for the TMDC. This article aims at increasing the awareness that Mo and Se co‐deposition does not automatically result in MoSe2 formation, but parasitic processes may trigger the growth of other TMDCs. [ABSTRACT FROM AUTHOR]