Rate Enhancement Research Articles

Role of the in situ formed LiAl(NH)2 and LiNH2 in significantly improving the hydrogen storage properties of the Mg(NH2)2-2LiH systems with Li3AlH6 addition

The Mg(NH2)2-2LiH system has attracted considerable interest due to its high hydrogen capacity and low theoretical dehydrogenation enthalpy. However, its practical application is limited by sluggish kinetics due to the slow mass transfer rate and the stable N-H bond. In response to these problems, this study introduced Li3AlH6 into the Mg(NH2)2-2LiH system, leveraging the mutual destabilization effects between lithium alanates and metal amides to attenuate the stability of the N-H bond in Mg(NH2)2. The results show that the Mg(NH2)2-2LiH-0.1Li3AlH6 composite can reversibly desorb/absorb hydrogen up to 4.33 wt% at 140 °C with an initial dehydrogenation temperature of 90 °C. This represents a significant improvement over the pristine sample's capacity of 1.23 wt% under the same conditions. Phase structure analyses reveal that the in situ formed LiAl(NH)2 and LiNH2 particles during ball milling play a crucial role in decreasing the energy required for cleaving the N-H bond, transferring mass, and initiating nucleation. Dehydrogenation curves suggest that the dehydrogenation process follows the Avrami-Erofe'ev equation, signifying that the process is controlled by both nucleation and diffusion processes. A pronounced correlation exists between dehydrogenation kinetic energy barriers and nucleation energy barriers of the dehydrogenation products. This finding implies that future reductions in operating temperature and enhancements of the dehydrogenation rate in the Mg(NH2)2-2LiH system can be achieved by decreasing the nucleation energy barriers of the dehydrogenation products.

Research on the Welding Process and Weld Formation in Multiple Solid-Flux Cored Wires Arc Hybrid Welding Process for Q960E Ultrahigh-Strength Steel.

This paper proposes a novel welding process for ultrahigh-strength steel. The effects of welding parameters on the welding process and weld formation were studied to obtain the optimal parameter window. It was found that the metal transfer modes of solid wires were primarily determined by electrical parameters, while flux-cored wires consistently exhibited multiple droplets per pulse. The one droplet per pulse possessed better welding stability and weld formation, whereas the short-circuiting transfer or one droplet multiple pulses easily caused abnormal arc ignition that decreased welding stability, which could easily lead to a "sawtooth-shaped" weld formation or weld offset towards one side with more spatters. Thus, the electrical parameters corresponding to one droplet per pulse were identified as the optimal parameter window. Furthermore, the weld zone (WZ) was predominantly composed of AF, and the heat-affected zone (HAZ) primarily consisted of TM and LM. Consequently, the welded joint still exhibited excellent mechanical properties, particularly toughness, despite higher welding heat input. The average tensile strength reached 928 MPa, and the impact absorbed energy at -40 °C for the WZ and HAZ were 54 J and 126 J, respectively. In addition, the application of triple-wire welding for ultrahigh-strength steel (UHSS) demonstrated a significant enhancement in post-weld deposition rate, with increases of 106% and 38% compared to single-wire and twin-wire welding techniques, respectively. This process not only utilized flux-cored wire to enhance the mechanical properties of joints but also achieved high deposition rate welding.

Kinetic isotope effects on hydrogen/deuterium disordering and ordering in ice crystals: A Raman and dielectric study of ice VI, XV, and XIX.

Ice XIX and ice XV are both partly hydrogen-ordered counterparts to disordered ice VI. The ice XIX → XV transition represents the only order-to-order transition in ice physics. Using Raman and dielectric spectroscopies, we investigate the ambient-pressure kinetics of the two individual steps in this transition in real time (of hours), that is, ice XIX → transient ice VI (the latter called VI‡) and ice VI‡ → ice XV. Hydrogen-disordered ice VI‡ appears intermittent between 101 and 120K, as inferred from the appearance and subsequent disappearance of the ice VI Raman marker bands. A comparison of the rate constants for the H2O ices reported here with those from D2O samples [Thoeny et al., J. Chem. Phys. 156, 154507 (2022)] reveals a large kinetic isotope effect for the ice XIX decay, but a much smaller one for the ice XV buildup. An enhancement of the classical overbarrier rate through quantum tunneling for the former can provide a possible explanation for this finding. The activation barriers for both transitions are in the 18-24kJ/mol range, which corresponds to the energy required to break a single hydrogen bond. These barriers do not show an H/D isotope effect and are the same, no matter whether they are derived from Raman scattering or from dielectric spectroscopy. These findings favor the notion that a dipolar reorientation, involving the breakage of a hydrogen bond, is the rate determining step at the order-to-order transition.

Phase transfer catalysts shift the pathway to transmetalation in biphasic Suzuki-Miyaura cross-couplings

The Suzuki-Miyaura coupling is a widely used C-C bond forming reaction. Numerous mechanistic studies have enabled the use of low catalyst loadings and broad functional group tolerance. However, the dominant mode of transmetalation remains controversial and likely depends on the conditions employed. Herein we detail a mechanistic study of the palladium-catalyzed Suzuki-Miyaura coupling under biphasic conditions. The use of phase transfer catalysts results in a remarkable 12-fold rate enhancement in the targeted system. A shift from an oxo-palladium based transmetalation to a boronate-based pathway lies at the root of this activity. Furthermore, a study of the impact of different water loadings reveals reducing the proportion of the aqueous phase increases the reaction rate, contrary to reaction conditions typically employed in the literature. The importance of these findings is highlighted by achieving an exceptionally broad substrate scope with benzylic electrophiles using a 10-fold reduction in catalyst loading relative to literature precedent.

An adaptive MLP-based joint optimization of resource allocation and relay selection in device-to-device communication using hybrid meta-heuristic algorithm

Enhancement in both energy efficiency and spectral efficiency in cellular networks is made possible by means of an advanced technique called device-to device (D2D) communication. The enhancement of these efficiencies is done by utilizing the cellular user (CU) resources once again to make communication with nearby cellular devices in an effective manner by spectral means. As the D2D communication technology is capable of providing a direct communication link with nearby devices effectively with enhanced spectral efficacy, this approach is considered as an ideal solution for the futuristic cellular communication network. A flexible and reliable relay-assisted communication by means of D2D technology is required that acts as an intermediate relay when the attenuation between the channels across the D2D devices becomes high. The throughput of the system is increased by utilizing D2D communication technology as it uses direct data transmission within cellular devices. When the cellular user is far apart from one another, the data loss in the D2D communication system is minimized with the utilization of the relay. When the channels are good, then the relay nodes (RNs) serve the cellular user. However, it is noted that the D2D systems are affected by issues such as higher consumption of energy and spectral sharing. Also, the sum rate gets degraded as a result of mutual interference between resource-sharing cellular devices in the relay-assisted D2D communication system. The transmission of the data in a traditional relay-assisted D2D communication system is carried out between the D2D receiver (DR) and D2D transmitter (DT) only with the utilization of its own energy by the RN. The issues in relay selection and resource allocation in the conventional joint resource allocation schemes are tackled by executing a scheme for performing the task of optimal relay selection and joint resource allocation. The enhancement of the overall sum rate in the D2D communication is the main motive behind the implemented scheme. This goal is attained along with the minimization of the link rates in the cellular and D2D networks. The ideal selection of the relay and the execution of the joint resource allocation are done with the utilization of a new optimization scheme called the hybrid flow direction with the chameleon swarm algorithm (HFDCSA), in which the flow direction algorithm (FDA) is fused along with chameleon swarm algorithm. This optimal selection of the relays is assisted by considering constraints like the network’s sum rate and energy efficiency in the network to achieve high performance. The data obtained from distinct sources are given to the adaptive multi-layer perceptron (AMLP) in which optimal resource allocation and the relay selection are performed with the help of the suggested HFDCSA. The parameters in the MLP are tuned by the same HFDCSA. Finally, the performance validation is conducted in the stage to verify the working of the suggested approach.

Solubility and Dissolution Rate Enhancement of Aceclofenac by Solid Dispersion Employing Kneading and Solvent Evaporation Techniques

Background: Aceclofenac (ACF) is a non-steroidal anti-inflammatory drug with potent anti-inflammatory and analgesic properties. ACF is belongs to BCS class II which has poor solubility in water (practically insoluble) and high permeability that leads to a low dissolution rate and reduced bioavailability. Objective: to enhance the solubility and dissolution rate of ACF using the solid dispersion method (SD) by two common techniques which were solvent evaporation (SE) and kneading (Kn) by using different carriers Mannitol, PVP k30, Soluplus®, and Urea in both techniques at 1:1 and 1:5 wight ratio. Methods: The effects of type of carrier and preparation method on solubility and dissolution rate of SD were studied. Solid dispersions were characterized for their, percentage yield, drug content, drug solubility and in-vitro dissolution rate in comparison with pure drug. Results: The best formula is obtained by the Kn formula (F16) which was formulated by the use of ACF: Soluplus®: with a weight ratio of 1:5 which gave a high percentage yield (99.5%), high drug content (99.8± 0.003%) and the best solubility enhancement which was 361 folds compared to pure ACF and faster dissolution rate which was 80% in 10 minutes compared to 20% for pure drug. Conclusion: the solubility and in-vitro dissolution rate of ACF was efficiently improved when prepared by SD techniques, utilizing both solvent evaporation and kneading methods. Furthermore, the kneading method was superior to solvent evaporation method due to the greater enhancement of solubility and dissolution rate obtained by all carriers and ratios with higher improvement by 1:5 ratio, and can be considered a successful and efficient strategy for solubility and in-vitro dissolution rate improvement of hydrophobic drugs.

Sodium chloride solution transport through a carbon nanotube with an embedded carbon nanotube via molecular dynamics simulations

Carbon nanotubes hold significant potential for developing highly efficient desalination membranes. However, achieving both enhanced water transfer rate and salt rejection efficiency simultaneously has been challenging due to the pore size limitation. In this study, we discovered that embedding a carbon nanotube within a large-diameter carbon nanotube enables the simultaneous enhancement of both water transfer rate and salt rejection efficiency. This outcome is attributed to the accelerated water velocity and the blockage of ions entering the narrowed cross-section of the carbon nanotube. These findings have valuable implications for the design of fast water transport membranes with high salt rejection efficiency.

Effects of Yacon (Smallanthus sonchifolius) Juice Byproduct Administered Using Different Feeding Methods on the Growth Performance, Digestive Enzyme Activity, Antioxidant Status, and Disease Resistance against Streptococcus iniae of Juvenile Black Rockfish (Sebastes schlegelii)

This study was designed to evaluate the effects of yacon (Smallanthus sonchifolius) juice byproduct (YJB) on the growth performance, digestive and antioxidant enzyme activities, and disease resistance against Streptococcus iniae of juvenile black rockfish (Sebastes schlegelii) based on different feeding schedules. Four different YJB feeding strategies were evaluated: feeding the fish a basal diet continuously (control, T0), feeding them YJB (2.5 g/kg) continuously (T1), feeding them YJB for 1 day and the basal diet the next day (T2), and feeding them YJB for 1 day and the basal diet for the following 2 days (T3). No difference in survival among the treatments was found after the 8-week feeding trial (p > 0.05). However, the T1 and T2 groups exhibited significant enhancements in final body weight, weight gain, and specific growth rate compared with the T0 and T3 groups. Furthermore, the T1 and T2 groups showed a significant improvement in feed consumption, feed efficiency, and protein efficiency ratio compared with the T0 and T3 groups. No significant differences in the condition factor or viscerosomatic and hepatosomatic indices were observed among all the groups. Intestinal amylase, trypsin, and lipase activity was significantly (p < 0.05) higher in the T1 and T2 groups than in the T0 and T3 groups. Lysozyme, superoxide dismutase, and catalase activity along with glutathione peroxidase content were significantly (p < 0.05) higher under all YJB feeding regimens than those under the control treatment. The survival rates in all the YJB treatment groups after the S. iniae challenge were significantly (p < 0.05) enhanced. In conclusion, we recommend offering YJB at day-to-day intervals to improve growth performance, digestive enzyme activity, antioxidant status, and disease resistance against S. iniae.

MicroRNA257 promotes secondary growth in hybrid poplar

Populus, a significant fast-growing tree species with global afforestation and energy potential, holds considerable economic value. The abundant production of secondary xylem by trees, which serves as a vital resource for industrial purposes and human sustenance, necessitates the orchestration of various regulatory mechanisms, encompassing transcriptional regulators and microRNAs (miRNAs). Nevertheless, the investigation of microRNA-mediated regulation of poplar secondary growth remains limited. In this study, we successfully isolated a novel microRNA (Pag-miR257) from 84 K poplar and subsequently integrated it into the 35 S overexpression vector. The overexpression of Pag-miR257 resulted in notable increases in plant height, stem diameter, and fresh weight. Additionally, the overexpression of Pag-miR257 demonstrated a significant enhancement in net photosynthetic rate. The findings from the examination of cell wall autofluorescence indicated a substantial increase in both xylem area and the number of vessels in poplar plants overexpressing Pag-miR257. Furthermore, the cell wall of the Pag-miR257 overexpressing plants exhibited thickening as observed through transmission electron microscopy. Moreover, the Fourier Transforms Infrared (FTIR) analysis and phloroglucinol-HCl staining revealed an elevation in lignin content in Pag-miR257 overexpressing poplar plants. The findings of this study suggest that microRNA257 may play a role in the control of secondary growth in poplar stems, thereby potentially enhancing the development of wood engineering techniques for improved material and energy production.

Enhanced peroxymonosulfate activation by δ-MnO2 nanocatalyst enriched with oxygen vacancies for phenolic pollutants polymerization

Heterogeneous advanced oxidation processes technology holds great potential for the removal of toxic phenolic molecules in water, but is currently challenged by overuse of oxidation agents and undesirable carbon emissions during the mineralization process. The present work demonstrates that with an oxygen-vacancy-rich Fe doped δ-phase MnO2 (δ-MnO2) as the nanocatalyst, the phenol (PhOH) could be removed with high selectivity as well as effective conversion into non-toxic phenolic polymers via a non-radical electron transfer route, instead of complete mineralization by common radical attacking route. Oxygen vacancies in δ-MnO2 were enriched by Fe doping, which greatly improved the activation of peroxymonosulfate (PMS) by extending the length of the O-O bond in PMS. A 6.68-fold enhancement of the removal rate of PhOH was achieved by Fe doping δ-MnO2, compared to the pristine δ-MnO2. Moreover, the consumption of PMS could be reduced by up to 95.08 %, and the carbon emissions were also reduced by up 99.13 % during the polymerization process. The present study manifests that rationally designing a non-radical route offers significant potential for the cost-effective use of oxidation agents as well as reducing carbon emissions, presenting a superior approach for the target of achieving carbon neutrality in environmental remediation.

Non-consecutive enzyme interactions within TCA cycle supramolecular assembly regulate carbon-nitrogen metabolism

Enzymes of the central metabolism tend to assemble into transient supramolecular complexes. However, the functional significance of the interactions, particularly between enzymes catalyzing non-consecutive reactions, remains unclear. Here, by co-localizing two non-consecutive enzymes of the TCA cycle from Bacillus subtilis, malate dehydrogenase (MDH) and isocitrate dehydrogenase (ICD), in phase separated droplets we show that MDH-ICD interaction leads to enzyme agglomeration with a concomitant enhancement of ICD catalytic rate and an apparent sequestration of its reaction product, 2-oxoglutarate. Theory demonstrates that MDH-mediated clustering of ICD molecules explains the observed phenomena. In vivo analyses reveal that MDH overexpression leads to accumulation of 2-oxoglutarate and reduction of fluxes flowing through both the catabolic and anabolic branches of the carbon-nitrogen intersection occupied by 2-oxoglutarate, resulting in impeded ammonium assimilation and reduced biomass production. Our findings suggest that the MDH-ICD interaction is an important coordinator of carbon-nitrogen metabolism.

Anion- and water-facilitated oxidative carbon–carbon bond cleavage and diketonate carboxylation in Cu(II) chlorodiketonate complexes

The O2-dependent carbon–carbon (CC) bond cleavage reactions of the mononuclear Cu(II) chlorodiketonate complexes [(6-Ph2TPA)Cu(PhC(O)CClC(O)Ph)]ClO4 (1-ClO4) and [(bpy)Cu(PhC(O)CClC(O)Ph)(ClO4)] (3-ClO4) have been further examined in terms of their anion and water dependence. The bpy-ligated Cu(II) chlorodiketonate complex 3-ClO4 is inherently more reactive with O2 than the 6-Ph2TPA-ligated analog 1-ClO4. Added chloride is needed to facilitate O2 reactivity for 1-ClO4 but not for 3-ClO4 at 25(1) °C. Evaluation of kobs for the reaction of 1-ClO4 with O2 under pseudo first-order conditions as a function of the amount of added chloride ion produced saturation type behavior. The bpy-ligated 3-ClO4 exhibits different behavior, with rate enhancement resulting from both the addition of chloride ion and water. Computational studies indicate that the presence of water lowers the barrier for O2 activation for 3-ClO4 by ∼12 kcal/mol whereas changing the anion from perchlorate to chloride has a smaller effect (lowering of the barrier by ∼3 kcal/mol). Notably, the effect of water for 3-ClO4 is of similar magnitude to the barrier-lowering chloride effect found in the O2 activation pathway for 1-ClO4. Thus, both systems involve lower energy O2 activation pathways available, albeit resulting from different ligand effects. Probing the effect of added benzoate anion, it was found that the chloro substituent in the diketonate moiety of 1-ClO4 and 3-ClO4 will undergo displacement upon treatment of each complex with tetrabutyl ammonium benzoate to give Cu(II) benzoyloxydiketonate complexes (4 and 5). Complexes 4 and 5 exhibit slow O2-dependent CC cleavage in the presence of added chloride ion. These results are discussed in the context of the chemistry identified for various divalent metal chlorodiketonate complexes, which have relevance to catalytic systems and metalloenzymes that mediate O2-dependent CC cleavage within diketonate substrates.

Production of diphenolic acid from bio-levulinic acid over MCF supported bimetallic phosphotungstic acid as catalyst: Enhancement in rate and selectivity under microwave irradiation

The para-isomer of diphenolic acid is widely accepted as a bio-based polymer precursor and a sustainable substitute for bisphenol A (BPA). In the current work, a bimetallic dodecatungstophosphoric acid salt catalyst supported on mesocellular foam (MCF) was employed to condense bio-derived levulinic acid and phenol under solvent-free conditions in the presence of microwaves to enhance rates of reaction, conversion and selectivity. Various parameters affecting conversion and selectivity were systematically studied. A study was done to investigate the factors that affect the reaction rate. A kinetic model was derived, and reaction mechanism proposed. The reaction proceeds with a second-order kinetics with an activation energy of 10.17 Kcal/mol and exhibits the Langmuir-Hinshelwood-Hougen-Watson (LHHW) mechanism. The catalyst was robust and could be repeatedly used. The overall process showed microwaves coupled with the new catalyst improved efficiency, selectivity, and sustainability in synthesizing diphenolic acid (DPA), offering new insights into the process.

Computational study of magnetohydrodynamic mixed convective flow in a nanofluid-filled cavity with diagonally moving lid

This study examines the phenomenon of uniform magnetohydrodynamic mixed convective flow in a cavity filled with nanofluid. The research focuses on analyzing the mixed convection induced by a uniformly heated lid-driven cavity with diagonal motion. The fluid and heat transport equations are solved using the finite volume method. Numerical simulations are conducted for various parameters including Richardson number (Ri) ranging as 0.1, 1 & 10, Hartmann number (Ha) 0, 10, 25 & 50, angle of inclination (γ) 0°, 30°, 45°, 60° & 90°, and solid volume fraction from 0.0 to 0.05. The results are presented in terms of flow and thermal fields. It is observed that higher Hartmann numbers and inclination angles of the magnetic field lead to a suppression of convection, favoring a dominant conduction mode and reducing the overall heat transfer rate. Specifically, the study highlights a significant enhancement in the heat transfer rate in a nanofluid-filled cavity with a diagonally moving wall. The movement’s of diagonal wall has significant power consumption, the tool may be used in an industrial process that improves heat transfer, offers flexibility, and raises the quality of the finished product. Additionally, the correlations that were found are a useful tool for heat exchanger design.

Confined Ionic Environments Tailoring the Reactivity of Molecules in the Micropores of BEA-Type Zeolite.

In the presence of water, hydronium ions formed within the micropores of zeolite H-BEA significantly influence the surrounding environment and the reactivity of organic substrates. The positive charge of these ions, coupled with the zeolite's negatively charged framework, results in an ionic environment that causes a strongly nonideal solvation behavior of cyclohexanol. This leads to a significantly higher excess chemical potential in the initial state and stabilizes at the same time the charged transition state in the dehydration of cyclohexanol. As a result, the free-energy barrier of the reaction is lowered, leading to a marked increase in the reaction rates. Nonetheless, there is a limit to the reaction rate enhancement by the hydronium ion concentration. Experiments conducted with low concentrations of reactants show that beyond an optimal concentration, the required spatial rearrangement between hydronium ions and cyclohexanols inhibits further increases in the reaction rate, leading to a peak in the intrinsic activity of hydronium ions. The quantification of excess chemical potential in both initial and transition states for zeolites H-BEA, along with findings from HMFI, provides a basis to generalize and predict rates for hydronium-ion-catalyzed dehydration reactions in Brønsted zeolites.

Symmetry Molecular Design Strategy for Highly Efficient Blue Electroluminescence with Hot Exciton Mechanisms

AbstractEmitters with a hot exciton mechanism are regarded as one of the most promising candidates for organic light‐emitting diodes (OLEDs). In this study, a deep‐blue emitter with the hot exciton mechanism is reported, namely 2An‐PCz, by integrating a pair of carbazole groups with a 9,9′‐bi‐anthracene nucleus. Owing to the symmetric molecular architecture and intrinsic local excited state character, multiple high‐lying reverse intersystem cross (hRISC) channels and large overlaps of frontier molecular orbits (FMOs) can be formed, facilitating rapid hRISC processes as well as enhancement of radiative transition rates simultaneously. Combined with the strong luminescence properties brought by the unique X‐packing mode, a high photoluminescence quantum yield of 60.5% is achieved in the non‐doped state. Strikingly, non‐doped deep‐blue OLEDs exhibited a maximum external quantum efficiency (EQE) of 10.50% with minimal efficient roll‐off, which is one of the highest values for deep‐blue organic light‐emitting devices based on hot exciton emitters thus far. The magneto‐electroluminescence (MEL) experiment and transient electroluminescence measurements corroborated that both the high EQE and suppressed efficiency roll‐off are attributable to the rapid “hot exciton” channels.

Fe3+-modified polyamide membrane with a porous network structure: Rapid permeation and efficient interception of trace organic compounds

Forward osmosis (FO) is a promising technology in the treatment of trace organic substances. However, the development of this technology is limited by membrane material selection and the long-term chemical stability and durability of the membrane. Whereas ibuprofen, a representative trace organic substances that is hydrophobic and negatively charged, poses potential environmental hazards due to its bioactivity. In this work, polyethersulfone (PES) membranes were modified with iron metal complexes via chelation reactions to achieve high rejection rates for ibuprofen. The Fe3+-modified composite FO membrane increased the ibuprofen rejection rate to 98.3 % compared to less than 80.0 % for the original PES membrane. Additionally, the modified membrane enhanced water flux by at least 25.0 % and reduced reverse solute flux to a maximum of 73.0 % of that of the polyamide composite membrane, while significantly improving anti-fouling capabilities. Membrane characterization results revealed that the significant enhancement in the ibuprofen retention rate was due to the addition of a negative charge by forming complexes with Fe3+, which increased intermolecular interactions. Additionally, the dense network structure developed by the Fe3+-EDTA-2Na modification also contributed to the enhanced membrane performance.

Manipulating interface-induced multi-channel charge transfers toward highly hierarchical synchronous g-C3N4/STO@Pt modulation for boosting artificial photosynthesis

For the transformation of energy conversion and photocatalytic decomposition, photocatalyst-based artificial photosynthesis for solar-to green fuels and environmental treatment has aroused great attention. Herein, a novel ternary heterojunction based on constructing an interaction between 2D-graphitic carbon nitride (CN), 3D-strontium titanate (STO) and Pt nanoparticles (NPs) (2D/3D CN/STO@Pt) is designed for the first time to greatly promote photocatalytic water cracking hydrogen (H2) evolution in an alkalescent environment, such as triethanolamine (TEO) as well as integrating with Rhodamin B (RhB) decomposition. Under optimized conditions, the H2 productivity over 3D/2D CN/STO@Pt-3 heterostructures (10,005 μmol h−1 g−1) with an apparent quantum yield of H2 production approaching 47.5% is found to be ∼29.7, 8.5, 1.1, and 1.5-fold as much as that in the CN, CN/STO, CN/STO@Pt-1, and CN/STO@Pt-5 heterojunctions, respectively. An up to 2.5-fold enhancement in the photocatalytic RhB decomposition rate, obtaining 90% within 60 min under visible-light-driven is observed for 3D/2D CN/STO@Pt-3 heterostructures, surpassing that of other samples. The CN/STO@Pt-3 sample shows the highest degradation rate of 3.5 min−1, which is 1.8, 2.8, 4.27 and 4.9 -time higher than that of the CN/STO@Pt-1, CN/STO@Pt-5, CN, and STO samples, respectively. The improved photocatalytic behavior of the heterogeneous structures could be ascribed to i) the type II-heterojunction between 2D CN and 3D STO; and ii) the creation of the Schottky contacts between semiconductors and Pt NPs. The configuration of the type-II heterojunction formed by the two semiconductors of 2D g-C3N4 and 3D STO contributes to improved light absorption ability, and rapid separation and transfer of photoinduced charges. At the same time, the close junction of Pt establishes the Schottky barrier to facilitate efficient electron transfer in the ternary nanostructures, impeding the quick recombination of photoexcited charge carriers, and offering abundant reactive sites, contributing multiple electron pathways for the photoreaction strategy. Increased photocurrent density from the LSV measurement and a declined in PL intensity confirmed the enhanced interfacial charge separation in the tertiary photocatalyst. Furthermore, the CN/STO@Pt-3 ternary heterostructure presents outstanding photocatalytic performance after five cycles, indicating good stability and reusability. This work gives a valuable modification pathway for the establishing multi-channel charge carrier transport for energy conversion and environmental remediation processes.

Highly efficient Z scheme heterojunction of colloidal SnO2 quantum dots grafted g-C3N4 for the degradation of rhodamine B under visible light

The strategic design of the heterojunction photocatalyst with an enhancement in the charge transfer rate of photogenerated charge carriers plays a key role in wastewater treatment to remove organic pollutants. In the current study, the heterojunction of g-C3N4/SnO2 quantum dots (g-CN/c-SQDs) with different ratios of SQDs was prepared via sonochemical route. The Z scheme for the photocatalyst of g-CN/c-SQDs in visible light exhibits an exceptional degradation performance of RhB dye (98.25 % in 40 min) with cyclic stability. The enhancement of photocatalytic degradation efficiency is ascribed to efficient charge transfer and redox reactions due to the design of the heterojunction between high surface areas of g-C3N4 and c-SQD, which is evident from the results from photoluminescence spectra and scavenger experiments. The free radical capture experiments reveal the electron transfer pathway and the generation of reactive oxygen species (ROS) generation, including superoxide (•O2–) and hydroxyl (•OH) radicals has been involved in the photocatalytic degradation process. This study provides an insight of the construction of the Z- scheme heterojunction with an appropriate amount of semiconductor for an enhancement of photodegradation efficiency in wastewater treatment.

Out-of-plane impact behavior and post-impact damage evaluation of GFRP bar-reinforced concrete shear walls in fire

Fiber-reinforced polymers (FRP) have been a prospective material in engineering. However, the attenuation of FRP bar-reinforced concrete members in fire is unclear. This paper studies the impact resistance of glass fiber-reinforced polymer bar-reinforced concrete (GFRP-RC) shear walls under high temperatures. Considering the impacts of strain rate enhancement and high temperature softening on GFRP bars and concrete, a numerical model with finite elements in three dimensions was created. To verify the model, three cases were simulated and compared with the test records, including the seismic performance of FRP-RC shear walls under axial compression, the seismic behavior of reinforced concrete (RC) shear walls under high temperatures, and RC shear walls' impact response. Based on the calibrated numerical model, the displacement, impact force, reaction force, failure mode, energy distribution, internal force and the residual shear bearing capacity of GFRP-RC shear wall subjected to impact under different fire times were analyzed. The influence of fire time on the failure mechanism of GFRP-RC shear walls was studied. Taking the mid-span displacement as the damage index, the evaluation criteria for the four damage levels were determined. The findings indicate that the type of reinforcement has little effect on the shape of impact force, reaction force and displacement time history curve. The peak values of impact force and reaction force of RC walls are larger than those of GFRP-RC shear walls, while the former has smaller peak displacements and residual displacements. The damage of shear walls becomes more severe as the fire time increases, as does the displacement. Also, the impact force, reaction force, shear force and bending moment decrease gradually. The energy absorbed by shear walls is primarily dissipated by concrete, the part by GFRP bars accounting for a small proportion. The post-impact residual bearing capacity of GFRP-RC shear walls is linearly related to the mid-span displacement under impact loads, primarily influenced by high-temperature exposure.