Kinetic Study of Ozone Photocatalytic Decomposition Using a Thin Film of TiO₂ Coated on a Glass Plate and the CFD Modeling Approach

The kinetics of ozone photocatalytic decomposition in a flow-through reactor using a thin film of TiO₂ coated on a glass plate is investigated. The Langmuir–Hinshelwood kinetic model provides a good description of the ozone decomposition. The effect of light intensity on reaction rate is also studied, showing a transition in the kinetic order with respect to light intensity occurred from 0.75 to 1.0 mW·cm^–2 under the experimental conditions. Fluid dynamics and surface photocatalytic reaction modeling by the computational fluid dynamic (CFD) approach is then proposed. The parameters determined in the kinetic experiment are used to calculate the ozone concentration distribution in the flow-through reactor under a given radiation field. In terms of conversion yield, the model predictions agree closely with the experimental results within the range in which the results are examined. This study presents a simple example of the photocatalytic reaction process modeling. Knowledge of the intrinsic kinetics allows the universal application of this CFD approach to the optimization and design of photocatalytic reactors

Metallic BSi₃ Silicene: A Promising High Capacity Anode Material for Lithium-Ion Batteries

Very recently, intrinsically metallic B-substituted silicenes, namely, <i>H</i>-BSi₃ and <i>R</i>-BSi₃ (<i>H</i> and <i>R</i> denote the hexagonal and rectangular symmetry), have been predicted as the global minimum structures of the BSi₃ monolayer (<i>J. Phys. Chem. C</i> <b>2014</b>, DOI: 10.1021/jp507011p). With unusual planar geometry and better electronic conductivity relative to the buckled and semimetallic pristine silicene sheet, the B-substituted silicenes are expected to have good applications in high capacity lithium-ion batteries (LIBs) anodes. By means of density functional theory (DFT) computations, we systematically investigated the adsorption and diffusion of Li on <i>H</i>-BSi₃ and <i>R</i>-BSi₃, in comparison with silicene and graphite. Their exceptional properties, including good electronic conductivity, very high theoretical charge capacity (1410 and 846 mA·h/g for single- and double-layer, respectively), fast Li diffusion, and low open-circuit voltage (OCV), suggest that the BSi₃ silicene could serve as a promising high capacity and fast charge/discharge rate anode material for LIBs

Borophene as a Promising Material for Charge-Modulated Switchable CO₂ Capture

Ideal carbon dioxide (CO₂) capture materials for practical applications should bind CO₂ molecules neither too weakly to limit good loading kinetics nor too strongly to limit facile release. Although charge-modulated switchable CO₂ capture has been proposed to be a controllable, highly selective, and reversible CO₂ capture strategy, the development of a practical gas-adsorbent material remains a great challenge. In this study, by means of density functional theory (DFT) calculations, we have examined the possibility of conductive borophene nanosheets as promising sorbent materials for charge-modulated switchable CO₂ capture. Our results reveal that the binding strength of CO₂ molecules on negatively charged borophene can be significantly enhanced by injecting extra electrons into the adsorbent. At saturation CO₂ capture coverage, the negatively charged borophene achieves CO₂ capture capacities up to 6.73 × 10¹⁴ cm^–2. In contrast to the other CO₂ capture methods, the CO₂ capture/release processes on negatively charged borophene are reversible with fast kinetics and can be easily controlled via switching on/off the charges carried by borophene nanosheets. Moreover, these negatively charged borophene nanosheets are highly selective for separating CO₂ from mixtures with CH₄, H₂, and/or N₂. This theoretical exploration will provide helpful guidance for identifying experimentally feasible, controllable, highly selective, and high-capacity CO₂ capture materials with ideal thermodynamics and reversibility

p‑Doped Graphene/Graphitic Carbon Nitride Hybrid Electrocatalysts: Unraveling Charge Transfer Mechanisms for Enhanced Hydrogen Evolution Reaction Performance

Recently, hybrid electrocatalyst systems involving an active layer of <i>g</i>-C₃N₄ on a conductive substrate of N-doped graphene (<i>g</i>-C₃N₄@NG) have been shown to achieve excellent efficiency for the hydrogen evolution reaction (HER) [e.g., Zheng, Y.; Jiao, Y.; Zhu, Y.; Li, L. H.; Han, Y.; Chen, Y.; Du, A.; Jaroniec, M.; Qiao, S. Z. Nat. Commun. 2014, 5, 3783]. We demonstrate here through first principle calculations examining various hybrid <i>g</i>-C₃N₄@MG (M = B, N, O, F, P. and S) electrocatalysts that the N-doped case may be regarded as an example of a more general modulation doping strategy – by which either electron donating or electron withdrawing features induced in the substrate can be exploited to promote the HER. Despite the intrinsically cathodic nature of the HER, our study reveals that <i>all</i> of the graphene substrates have an increasingly electron withdrawing influence on the <i>g</i>-C₃N₄ active layer as H atom coverage increases, modulating binding of the H atom intermediates, the overpotential, and the likely operational coverage. In this context, it is not surprising that p-doping of the substrate can further enhance the effect. Our calculations show that B is the most promising doping element for <i>g</i>-C₃N₄@MG (M = B, N, O, F, P, and S) electrocatalysts due to the predicted overpotential of 0.06 eV at full coverage and a large interfacial adhesion energy of −1.30 eV, offering prospects for significant improvement over the n-dopant systems such as <i>g</i>-C₃N₄@NG that have appeared in the literature to date. These theoretical results reveal a more general principle for rational design of hybrid electrocatalysts, via manipulation of the Fermi level of the underlying conductive substrate

Controllable Electrocatalytic to Photocatalytic Conversion in Ferroelectric Heterostructures

Photocatalytic and electrocatalytic reactions to produce value-added chemicals offer promising solutions for addressing the energy crisis and environmental pollution. Photocatalysis is driven by light excitation and charge separation and relies on semiconducting catalysts, while electrocatalysis is driven by external electric current and is mostly based on metallic catalysts with high electrical conductivity. Due to the distinct reaction mechanism, the conversion between the two catalytic types has remained largely unexplored. Herein, by means of density functional theory (DFT) simulations, we demonstrated that the ferroelectric heterostructures Mo-BN@In2Se3 and WSe2@In2Se3 can exhibit semiconducting or metallic features depending on the polarization direction as a result of the built-in field and electron transfer. Using the nitrogen reduction reaction (NRR) and hydrogen evolution reaction (HER) as examples, the metallic heterostructures act as excellent electrocatalysts for these reactions, while the semiconducting heterostructures serve as the corresponding photocatalysts with improved optical absorption, enhanced charge separation, and low Gibbs free energy change. The findings not only bridge physical phenomena of the electronic phase transition with chemical reactions but also offer a new and feasible approach to significantly improve the catalytic efficiency

Conductive Boron-Doped Graphene as an Ideal Material for Electrocatalytically Switchable and High-Capacity Hydrogen Storage

Electrocatalytic, switchable hydrogen storage promises both tunable kinetics and facile reversibility without the need for specific catalysts. The feasibility of this approach relies on having materials that are easy to synthesize, possessing good electrical conductivities. Graphitic carbon nitride (g-C₄N₃) has been predicted to display charge-responsive binding with molecular hydrogenthe only such conductive sorbent material that has been discovered to date. As yet, however, this conductive variant of graphitic carbon nitride is not readily synthesized by scalable methods. Here, we examine the possibility of conductive and easily synthesized boron-doped graphene nanosheets (B-doped graphene) as sorbent materials for practical applications of electrocatalytically switchable hydrogen storage. Using first-principle calculations, we find that the adsorption energy of H₂ molecules on B-doped graphene can be dramatically enhanced by removing electrons from and thereby positively charging the adsorbent. Thus, by controlling charge injected or depleted from the adsorbent, one can effectively tune the storage/release processes which occur spontaneously without any energy barriers. At full hydrogen coverage, the positively charged BC₅ achieves high storage capacities up to 5.3 wt %. Importantly, B-doped graphene, such as BC₄₉, BC₇, and BC₅, have good electrical conductivity and can be easily synthesized by scalable methods, which positions this class of material as a very good candidate for charge injection/release. These predictions pave the route for practical implementation of electrocatalytic systems with switchable storage/release capacities that offer high capacity for hydrogen storage

High Activity Ti³⁺-Modified Brookite TiO₂/Graphene Nanocomposites with Specific Facets Exposed for Water Splitting

Brookite TiO₂ exhibits promising photocatalytic activity in photoreduction; however, it is least known due to poor stability. We have synthesized Ti³⁺-modified brookite TiO₂/graphene nanocomposites with specific facets exposed successfully. They show highly improved photoreduction activity for water splitting into H₂ with excellent stability. The well-crystallized brookite TiO₂ nanorods are surrounded by four reductive (211) facets with high conduction band potential and growth along the [001] direction, indicating that they have high photoreduction ability because more reductive electrons will be excited. By combining spectroscopic techniques and electrochemical analysis methods, the outstanding activity could be linked with the synergistic effects of highly exposed (211) facets, Ti³⁺ defects, and graphene. Their formation mechanism and the effects in the enhanced photoreduction activity have been discussed in detail. In addition to promoting the separation of photogenerated e^––h⁺ pairs effectively, the midgap state was introduced and the absorption ability was improved

Charge-modulated permeability and selectivity in graphdiyne for hydrogen purification

<p>Using first-principle calculations, we show that injecting positive charges into graphdiyne can substantially improve its hydrogen purification capability. When positive charges are introduced, the H₂ penetration barrier decreases while the penetration barriers of CO and CH₄ are significantly increased, hence leading to enhanced permeability and selectivity for hydrogen purification from CO and CH₄. These predictions show that application of positive charge provides a unique pathway, which avoids complicated synthesis routes, to enhance hydrogen purification performance, and may prove to be instrumental in searching for a new class of high-permeability and high-selectivity molecular-sieving membranes.</p

Formation and Migration of Oxygen Vacancies in SrCoO₃ and Their Effect on Oxygen Evolution Reactions

Perovskite SrCoO₃ is a potentially useful material for promoting the electrocatalytic oxygen evolution reaction, with high activities predicted theoretically and observed experimentally for closely related doped perovskite materials. However, complete stoichiometric oxidation is very difficult to realize experimentallyin almost all cases there are significant fractions of oxygen vacancies present. Here, using first-principles calculations we study oxygen vacancies in perovskite SrCoO₃ from thermodynamic, electronic, and kinetic points of view. We find that an oxygen vacancy donates two electrons to neighboring Co sites in the form of localized charge. The formation energy of a single vacancy is very low and is estimated to be 1.26 eV in the dilute limit. We find that a vacancy is quite mobile with a migration energy of ∼0.5 eV. Moreover, we predict that oxygen vacancies exhibit a tendency toward clustering, which is in accordance with the material’s ability to form a variety of oxygen-deficient structures. These vacancies have a profound effect on the material’s ability to facilitate OER, increasing the overpotential from ∼0.3 V for the perfect material to ∼0.7 V for defective surfaces. A moderate compressive biaxial strain (2%) is predicted here to increase the surface oxygen vacancy formation energy by ca. 30%, thus reducing the concentration of surface vacancies and thereby preserving the OER activity of the material

Data_Sheet_1_Disease-modifying therapy in progressive multiple sclerosis: a systematic review and network meta-analysis of randomized controlled trials.PDF

BackgroundCurrently, disease-modifying therapies (DMTs) for progressive multiple sclerosis (PMS) are widely used in clinical practice. At the same time, there are a variety of drug options for DMTs, but the effect of the drugs that can better relieve symptoms and improve the prognosis are still inconclusive.ObjectivesThis systematic review aimed to evaluate the efficacy and safety of DMTs for PMS and to identify the best among these drugs.MethodsMEDLINE, EMBASE, the Cochrane Library, and clinicaltrials.gov were systematically searched to identify relevant studies published before 30 January, 2023. We assessed the certainty of the evidence using the confidence in the network meta-analysis (CINeMA) framework. We estimated the summary risk ratio (RR) for dichotomous outcomes and mean differences (MD) for continuous outcomes with 95% credible intervals (CrIs).ResultsWe included 18 randomized controlled trials (RCTs) involving 9,234 patients in the study. DMT can effectively control the disease progression of MS. Among them, mitoxantrone, siponimod, and ocrelizumab are superior to other drug options in delaying disease progression (high certainty). Mitoxantrone was the best (with high certainty) for mitigating deterioration (progression of disability). Ocrelizumab performed best on the pre- and post-treatment Timed 25-Foot Walk test (T25FW; low certainty), as did all other agents (RR range: 1.12–1.05). In the 9-Hole Peg Test (9HPT), natalizumab performed the best (high certainty), as did all other agents (RR range: 1.59–1.09). In terms of imaging, IFN-beta-1b performed better on the new T2 hypointense lesion on contrast, before and after treatment (high certainty), while siponimod performed best on the change from baseline in the total volume of lesions on T2-weighted image contrast before and after treatment (high certainty), and sWASO had the highest area under the curve (SUCRA) value (100%). In terms of adverse events (AEs), rituximab (RR 1.01), and laquinimod (RR 1.02) were more effective than the placebo (high certainty). In terms of serious adverse events (SAEs), natalizumab (RR 1.09), and ocrelizumab (RR 1.07) were safer than placebo (high certainty).ConclusionDMTs can effectively control disease progression and reduce disease deterioration during the treatment of PMS.Systematic review registrationhttps://inplasy.com/?s=202320071, identifier: 202320071.</p