Reaction Kinetics Research Articles

Evaluating a hybrid process of anaerobic digestion, aerobic degradation, and electrochemical separation for swine wastewater treatment with methane and nutrient recovery

A hybrid process of anaerobic digestion (AD), aerobic degradation, and electrochemical separation was evaluated for treating real swine wastewater that is rich in organic and nutrient to achieve methane and nutrient recovery and industry standard discharge quality. Fe anode electrocoagulation and Mg anode struvite electrochemical precipitation (SEP) were evaluated as AD pretreatments. Both removed partial chemical oxygen demand (COD) from raw swine wastewater, but only SEP slightly enhanced the methane yield of pretreated swine wastewater. The SEP efficiency of the AD effluent was significantly better than raw swine wastewater. A further coupled micro/ultra-filtration produced high-purity (96%) struvite. SEP and struvite chemical precipitation (SCP) were evaluated for AD effluent treatment. This showed that compared with SCP following first-order reaction kinetics (reaction rate constant of 0.791 and 0.854 h−1 for NH4+-N and PO43--P), SEP not only achieved better removal of COD, NH4+-N and PO43--P, but was also shown to follow zero-order reaction kinetics (reaction rate constant of 5.72 and 5.78 mmol L−1 h−1 for NH4+-N and PO43--P). The SEP and SCP treated AD effluent was evaluated by conventional activated sludge (CAS), showing faster COD removal (first-order reaction rate constant of 0. 213 and 0.163 h−1) and lower residual COD (150 and 248 mg L−1) from SEP than SCP treated AD effluent, making the final effluent well below Chinese livestock wastewater discharge standards. Therefore, an emerging hybrid anaerobic membrane bioreactor (AnMBR)-SEP-CAS is proposed for swine wastewater treatment and proved to be more economically viable than the conventional hybrid AD-SCP-CAS process via cost-benefit analysis.

High-volume recycled glass cementitious and geopolymer composites incorporating graphene oxide

This study presents the development of high-volume recycled glass construction materials using recycled glass aggregate (RGA) as a 100 % sand replacement, recycled glass powder (RGP) as 40 wt% of the binder, and 0.1 wt% graphene oxide (GO) as nano-reinforcement. The research investigates the individual and their combined effects on the engineering performance, reaction kinetics (using calorimetry, X-ray diffraction-XRD, Fourier Transform Infrared-FTIR and Thermogravimetric analysis-TGA), and microstructure (Scanning Electron Microscopy/ Energy Dispersive X-ray Spectroscopy-SEM/EDS) for both cementitious and geopolymer systems. The results indicate that while RGA reduces strength and exacerbates alkali-silica reaction (ASR), the presence of 40 wt% RGP significantly mitigates ASR despite a lower strength gain in both systems. Geopolymers exhibit significantly lower ASR expansion compared to cementitious matrices owing to their superior alkali-binding capacity and denser microstructure, which restricts water and alkali ion mobility. 0.1 wt% GO was found to accelerate geopolymerisation, enhancing the strength of geopolymer mixes, but it decreased compressive strength in cement-based mixes due to self-desiccation-induced micro-cracking under ambient curing condition. The study also highlights that cement and metasilicate, as well as slag, are the main contributors to cost and CO2 emissions in cementitious and geopolymer systems, respectively. Overall, geopolymers exhibit a significantly lower global warming potential (< 180 kg CO2-eq/m3) compared to cement-based mixes (> 365 kg CO2-eq/m3) with a comparable cost (190–230 AUD/m3). The results indicate the potential for sustainable construction applications using high volumes of recycled glass, incorporating over 70 % of the mixture by weight.

Deeper insights into the devolatilization mechanism of biomass fixed-bed gasification under various atmospheres

In recent years, biomass oxy-fuel gasification has prompted increased interest for its ability to produce a gas with low tar content and to assist in carbon reduction. It is noteworthy that the type of atmosphere is a crucial factor influencing the devolatilization process in biomass gasification and the specific mechanisms by which an oxy-fuel atmosphere influences the devolatilization process remain inadequately explored. This work aimed to investigate the effect of various reaction atmospheres on devolatilization behavior, reaction kinetics, intermediate product formation, and biochar functional groups (BFGs) evolution. In comparison to an inert atmosphere, the oxy-fuel atmosphere facilitated the release of volatiles, and enhanced energy self-sustainability within the devolatilization system. The presence of O2 and CO2 promoted the generation of potential anhydrosugars while suppressing the formation of phenolic compounds. The synergistic effect present in the oxy-fuel atmosphere augments the exothermic effect and promotes the release of volatile and alkane gases during the devolatilization process. Furthermore, as oxygen concentrations increased in the reaction atmosphere, the sequential response of BFGs primarily followed the order: C-O → aromatic ring → C-OH/C–H/COO– → C=O. Moreover, advanced characterization analyses revealed that the oxy-fuel environment was more effective in promoting the aromatization and pore structure of biochar than an inert atmosphere. Collectively, these findings have substantial implications for reaction modeling in biomass fixed-bed gasification under real gas atmospheres and guide future research on tar control strategies.

Improving the coverage area and flake size of ReS2 through machine learning in APCVD

Machine learning is playing a crucial role in optimizing material synthesis, particularly in scenarios where several parameters related to growth exhibit different and significant outcomes. An example of such complexity is the growth of atomically thin semiconductors through chemical vapor deposition (CVD), where multiple parameters can influence the thermodynamics and reaction kinetics involved in the synthesis. Herein, we performed a set of orthogonal experiments, varying the key parameters such as temperature, carries gas flux and precursor position to identify the optimal conditions for maximizing covered area and the size of rhenium disulfide (ReS2) crystals. The experimental results were used to establish correlations among the three thermodynamic variables through an artificial neural network. Contour plots were then generated to visualize the impact on the coverage and flake size of the crystals. This study demonstrates the capability of machine learning to enhance the potential of CVD-growth for the integration of 2D semiconductors like ReS2at larger scales.

Vanadate-Mediated Mismatch Configuration over the Reconstructed Nickel-Iron Electrocatalyst for Boosting Alkaline Oxygen Evolution.

During the oxygen evolution reaction (OER), catalyst candidates that can fully trigger self-reconstruction to derive active species with favorable configurations are expected to overcome the sluggish reaction kinetics. Herein, we innovatively propose the introduction of heterogeneous vanadate dopants into nickel-iron alloy precatalysts, where the crystal mismatch structure induces local electron delocalization in the hexagonal close packed alloy phase, thereby facilitating adequate electrochemical reconstruction to form (oxy)hydroxides as the real catalytic species. Simultaneously, the participation of vanadate in the reconstruction also triggers mismatch in the derived (oxy)hydroxides, reinforcing the metal-oxygen covalence, so that lattice oxygen activation is kinetically favorable and facilitates the OER via the lattice oxygen pathway. Optimized reconstructed catalyst r-NiFeVOx-NF exhibits a low overpotential of 220 mV at current densities of 10 mA cm-2 and considerably stable operation. Our study opens up opportunities for achieving robust OER performance through the design and fabrication of the mismatch catalytic configuration.

Phenanthridine-based Covalent Organic Frameworks for Boosting Overall Solar H2O2 Production.

Solar-driven H2O2 production via the oxygen reduction reaction (ORR) and water oxidation reaction (WOR) dual channels is green and sustainable, but severely restricted by the sluggish reaction kinetics. Constructing intriguing photocatalysts with effective active centers is a shortcut to breaking the kinetic bottleneck with great significance. Herein, we synthesize two novel neutral phenanthridine-based covalent organic frameworks (PD-COF1 and PD-COF2) for photosynthesizing H2O2. Compared to the no phenanthridine counterpart (AN-COF), the H2O2 photosynthetic activities of PD-COF1 and PD-COF2 are markedly boosted. In air and pure water without sacrificial agents, under Xe lamp and natural sunlight, the H2O2 photogeneration rate of PD-COF2 is 6103 and 3646 μmol g-1 h-1, respectively. Further experimental and theoretical inspections demonstrate that introducing phenanthridine units into COFs smoothly modulates the charge carrier dynamics and thermodynamically favors the generation of crucial OOH* and OH* intermediates in the ORR and WOR paths, respectively. Additionally, this is the first time the neutral phenanthridine moiety serves as the photooxidation unit for 2e- WOR towards H2O2 photoproduction. The current work sheds light on exploring novel catalytic centers for high-performance H2O2 evolution.

Robust mussel-inspired LBL carbon nanotube-based superhydrophobic polyurethane sponge for efficient oil–water separation utilizing photothermal effect

Superhydrophobic materials possessing efficient and rapid oil–water separation capabilities, as well as robustness, have emerged as the epicenter of global attention. Conventional three-dimensional adsorbent materials often succumb to impaired performance under extreme environmental conditions, rendering it arduous to ensure the efficacy of oil–water separation, and confining the application scenarios. In this study, polyurethane sponges (PUs) co-modified with stearic acid (SA), polydimethylsiloxane (PDMS), and multi-walled carbon nanotubes (MWCNTs), designated as SA-PDMS/MWCNTs@PU (SPMPU), were successfully synthesized via layer-by-layer (LBL) self-assembly and liquid-phase deposition. The SPMPU sponge exhibits an overall separation efficiency of not less than 90 %. It boasts a stable adsorption capacity, formidable mechanical properties, and commendable reusability. SPMPU sponges maintain unparalleled stability in extreme environments, such as strong acids and alkalis, and in the photothermal effect experiment, the SPMPU sponge can attain a temperature of 101.5 °C within 2 min, with rapid reaction kinetics, high efficiency, and unwavering stability. Through the photothermal effect-assisted oil–water separation, a reliable solution is furnished for the current oil–water separation endeavors. The SPMPU sponge preparation is uncomplicated, economical, and yields stable performance, holding significant potential for application in marine oil spills and industrial oil–water separation scenarios.

Cutting-Edge Progress in Aqueous Zn-S Batteries: Innovations in Cathodes, Electrolytes, and Mediators.

Rechargeable aqueous zinc-sulfur batteries (AZSBs) are emerging as prominent candidates for next-generation energy storage devices owing to their affordability, non-toxicity, environmental friendliness, non-flammability, and use of earth-abundant electrodes and aqueous electrolytes. However, AZSBs currently face challenges in achieving satisfied electrochemical performance due to slow kinetic reactions and limited stability. Therefore, further research and improvement efforts are crucial for advancing AZSBs technology. In this comprehensive review, it is delved into the primary mechanisms governing AZSBs, assess recent advancements in the field, and analyse pivotal modifications made to electrodes and electrolytes to enhance AZSBs performance. This includes the development of novel host materials for sulfur (S) cathodes, which are capable of supporting higher S loading capacities and the refinement of electrolyte compositions to improve ionic conductivity and stability. Moreover, the potential applications of AZSBs across various energy platforms and evaluate their market viability based on recent scholarly contributions is explored. By doing so, this review provides a visionary outlook on future research directions for AZSBs, driving continuous advancements in stable AZSBs technology and deepening the understanding of their charge-discharge dynamics. The insights presented in this review signify a significant step toward a sustainable energy future powered by renewable sources.

Sparkling Synergy: Enhancing Hydrogen Evolution with a Mesoporous CoP/FeP Interface.

The reaction kinetics is predominantly determined by the surface and interface engineering of electrocatalysts. Herein, we demonstrate the growth of cobalt monophosphide and iron monophosphide (CoP/FeP) with an effective solid interface. The surface of CoP/FeP is mesoporous, which is obtained by phosphidizing mesoporous CoFe2O4. The CoP/FeP electrode exhibits substantially superior hydrogen evolution reaction (HER) performance compared to CoP and FeP. The overpotentials (η) required to generate 10 mA cm-2 are determined to be around 98 mVRHE (CoP/FeP), 220 mVRHE (FeP), and 265 mVRHE (CoP) in an acidic electrolyte. The exchange current density and Tafel slopes suggest that CoP/FeP has better redox properties and kinetic abilities compared to FeP and CoP. Furthermore, the CoP/FeP electrode exhibits reduced electrochemical impedance and superior surface charge transport characteristics in comparison to both the CoP and FeP electrodes. In addition to having a greater number of catalytically active sites, the turnover frequency of CoP/FeP is approximately 2 and 5 times higher than that of FeP and CoP, respectively. The CoP/FeP electrode maintains a consistent current density of around 25 mA cm-2 for a continuous period of 24 h during the HER, attesting to the excellent durability of the CoP/FeP electrode. In addition, a relationship between differential hydrogen adsorption energy (ΔEH), the corresponding Gibbs free energy change (ΔGH), and the hydrogen coverage on distinct surfaces, namely, CoP, FeP, and CoP/FeP, is established. The calculation findings show that the CoP/FeP surface, which is predominantly exposed with CoP, exhibits the highest catalytic potential for the HER. The estimation of the specific HER activity of the electrodes, normalized to the electrochemically active surface area, corroborates the calculation findings.

Electrochemical in-situ probing of heterocatalytic green reduction of 4-nitroaniline by novel non-noble CuO/Co3O4 nanocomposites

Nobel metals are commonly used catalysts in reactions due to their excellent catalytic activities. Transition metals, too, possess good catalytic activity due to the availability of vacant d-orbitals that provide avenues for electron exchange during reactions. In this work, the performance of CuO/Co3O4 (CCO) catalyst is evaluated. The catalyst is prepared by a facile coprecipitation method. X-ray diffraction, Fourier transform infrared spectroscopy, HRTEM, Ultraviolet spectroscopy, Scanning electron microscopy and X-ray photoelectron spectroscopy techniques were used to study the material properties. XRD analysis confirms the formation of CCO heterostructure with supporting evidence from FTIR, HRTEM and XPS. The catalyst shows optical bandgap contributions of CuO and Co3O4 at 1.6 eV and 2.4 eV, respectively. The SEM analysis shows the presence of agglomerates with a mean length of 111 ± 3 nm. The prepared catalyst is employed for the 4-nitroaniline reduction using sodium borohydride. The kinetics of the reduction reaction were studied, and an apparent rate constant of 0.323 min−1 was estimated. The catalyst shows a turnover frequency of 1.44 min−1 and 100% recyclability up to 5 cycles that are competitive with noble metal and rare-earth-based catalysts. The fast reduction of 4-NA is attributed to the novel p-p type isojunction formed by the heterostructure of CCO. Additionally, extensive electrochemical analysis has been used as an in situ probe to monitor the reduction reaction. Accordingly, the study shows the different intermediary reduction species formed in the process of reduction, adding evidence to the proposed mechanism.

Temperature-Dependent Oxidation Behavior of Silicon Carbide Surface: Reactive Molecular Dynamics Simulations.

The high-temperature oxidation mechanism of silicon carbide (SiC) is crucial for designing thermal protection systems in aircraft. This study explored the oxidative chemical reaction processes and mechanism on SiC surface and interfaces within the temperature range of 300-2300 K by using reactive molecular dynamics simulation. The oxygen impact on the silica (SiOx) growth of the SiC surface was analyzed, which shows a progressive increase of silica thickness. The simulation results indicated that the oxidation process of SiC was a typical passive oxidation mechanism. With the environmental temperature rising and oxygen impact, the increase of oxidation thickness on the SiC surface undergoes three oxidizing reaction processes: little chemical adsorption of oxygen molecules on the initial surface, rapid oxidation of silicon and carbon, and dramatic oxidation of the interface between the oxidation layer and SiC. Additionally, this work studied the mechanism of oxidation thickness growth and chemical diffusion of oxygen. The oxidation rate is weakened according to the oxygen atom diffusion barrier effect of silica repulsion. Moreover, the kinetic parameters were statistically calculated by fitting the growth of Si-O bonds and their reaction rate constants. Subsequently, the activation energy and pre-exponential factors were derived by using the Arrhenius equation to model the chemical reaction kinetics of the thermal oxidation process. The chemical reaction behaviors of the two stages could be concluded as follows: (i) in stage I, the initial oxidation is reaction rate limiting; (ii) in stage II, SiC oxidation is limited by both the oxidation reaction rate and the oxygen diffusion coefficient of the oxidation layer. The activation energy of stage II increased compared with stage I due to the oxygen atoms diffusion barrier between the oxidation layers. This study on the oxidation and ablation mechanism of the SiC surface at the atomic scale would provide insight into understanding thermal oxidation behavior and the design of ceramic materials.

Highly Acidic Electron-Rich Brønsted Acids Accelerate Asymmetric Pictet-Spengler Reactions by Virtue of Stabilizing Cation-π Interactions.

Electron-rich heteroaromatic imidodiphosphorimidates (IDPis) catalyze the asymmetric Pictet-Spengler reaction of N-carbamoyl-β-arylethylamines with high stereochemical precision. This particular class of catalysts furthermore provides a vital rate enhancement compared to related Brønsted acids. Here we present experimental studies on the underlying reaction kinetics that shed light on the specific origins of rate acceleration. Analysis of Hammett plots, kinetic isotope effects, reaction orders, Eyring plots, and isotopic scrambling experiments, allowed us to gather insights into the molecular interactions between the chiral Brønsted acid and catalytically formed intermediates. Based on rigorously determined pKa values as well as the experimental evidence, we propose that attractive intermolecular forces offered by electron-rich π-surfaces of the chiral counteranion enthalpically stabilize cationic intermediates and transition states by way of cation-π interactions. This view is furthermore supported by in-depth density functional theory calculations. Our deepened understanding of the reaction mechanism allowed us to develop a method for accessing 1-aryltetrahydroisoquinolines from aromatic dimethyl acetals, a substrate class that was thus far inaccessible via catalytic asymmetric Pictet-Spengler reactions.

Kinetic research of red mud waste oxidative pyrolysis and comparison under different atmospheres

Red mud, as a solid waste with high alkalinity, had a detrimental impact on the environment and required urgent attention. Currently, the mass processing and consumption of red mud were typically conducted under thermal conditions, so it was essential to gain a comprehensive understanding of the oxidative pyrolysis process. The thermogravimetric experiments were conducted at multiple heating rates in air and exhibited three obvious stages. The activation energy and reaction mechanism of three oxidative pyrolysis stages were explored using model-free and model-fitting methods, revealing the activation energies of 162.2, 265.8, 214.1 kJ/mol and the most suitable reaction mechanisms of g(α)=[-ln(1-α)]³, g(α)=1-(1-α)1/⁴, g(α)=[-ln(1-α)]1/2 for each stage, respectively. Furthermore, the estimated kinetic parameters and reaction mechanisms were applied to extra heating rate to verify the accuracy. More important, the effect of air on the pyrolysis process of red mud was examined by comparing the results with those obtained from pure nitrogen pyrolysis. The obtained oxidative pyrolysis characteristics of red mud could provide valuable insights of its co-pyrolysis or combustion for resources recycling.

Organic Carbon Reaction Kinetics in Bioturbated Sediments

AbstractMost organic carbon delivered to the seafloor is degraded within the bioturbated layer. Theory and empirical evidence have shown that organic carbon reactivity relates to the age of a particle. However, due to particle mixing, the age‐depth linear relation induced by sediment accretion is obfuscated. Here we combine a Lagrangian particle tracking model that resolves the age distribution of particles in the bioturbated zone and couple it to age‐dependent organic carbon degradation. Depth profiles for organic carbon concentration, reactivity and degradation rate are presented for sediments receiving low and high reactivity organic carbon in coastal, continental slope and deep‐sea environments. Our results show that a simple first‐order kinetics model suffices for well‐mixed sediments and systems receiving pre‐processed materials. A reactive continuum approach is needed for poorly mixed sediments receiving highly reactive organic carbon and for sediments below the bioturbated layer.

NiCo2O4-based wool-ball as an electrocatalyst for methanol assisted water splitting, an alternative to water splitting

Hydrogen energy is considered a potential solution to the energy crisis and environmental pollution concerns. Pure hydrogen can be produced from electrochemical water splitting, however, the oxygen evolution reaction (OER) is the primary obstacle due to its sluggish reaction kinetics. Introducing methanol oxidation is one possible solution to replace OER for water splitting to produce hydrogen as an energy source. In this article, a NiCo₂O₄-based wool-ball electrocatalyst was prepared via a solvothermal process followed by annealing. The catalyst showed high purity and a wool-ball structure, where the threads are arranged in different patterns and composed of sub-nano-sized spheres. The catalyst exhibited an excellent response to oxidation reactions and reduced severely the potential for 250 mV, when 1.17 mM of methanol was introduced into a 1 M KOH solution. The catalyst also demonstrated good performance for the hydrogen evolution reaction (HER), however, there was a reduction in performance in the presence of methanol. This might be due to the formation of a methanol layer that inhibits the HER in the KOH solution, as methanol does not participate in HER. This resistance was confirmed with electrochemical impedance spectroscopy (EIS) and electrochemical surface area (ECSA) measurements, where the ECSA value in KOH was 4.10, which reduced to 2.63 in the presence of methanol. The catalyst exhibited excellent stability for both HER and methanol oxidation reaction (MOR) over a long duration of 3600 s.

Construction of carbon hybridized Co3S4/NiS microspheres on nickel foam for enhanced electrocatalytic hydrogen evolution in all-pH water and seawater

Interface engineering can expose sufficient active sites and facilitate the hydrogen evolution reaction kinetics. Herein, we developed a strategy with the designed deep eutectic solvents dissolved CoO as precursors to prepare Co3S4 and NiS nanodots and carbon hybridized microspheres on the surface of nickel foam (Co3S4/NiS/C/NF) via a one-step sulfidation-pyrolysis method. The composite catalysts have abundant tightly coupled heterogeneous interfaces between Co3S4 and NiS nanodots, the hybridized carbon layers and NF, which not only improve the electron transfer efficiency but also increase the number of active sites. The optimized Co3S4/NiS/C/NF electrodes exhibit excellent electrocatalytic HER activity in all-pH water and natural seawater, and were even superior to the Pt/C electrode at high current densities. In 0.5 M H2SO4, 1.0 M KOH, 1.0 M PBS, and natural seawater electrolytes, current densities as high as 10 mA cm−2 were obtained at remarkably low overpotentials of only 49, 72, 93, and 261 mV respectively. This work provides new insights for the development of excellent electrocatalysts in all-pH water and natural seawater applications.

Study of Exhaust Gas Composition and Dilution Effects on Diesel Spray Ignition Characteristics

ABSTRACT Exhaust gas retained in a cylinder is unavoidable, affecting diesel spray ignition. However, its effects on diesel spray ignition characteristics are not completely clear so far, due to the coupled and complicated function of exhaust gas compositions and dilution effects. To reveal the effect mechanism, three-dimensional simulations and chemical kinetics calculations were performed. The results illustrate that with the rise of exhaust gas rate, the initial position of the flame moves downward due to the longer ignition delay. The introduction of exhaust gas compositions decreases both the low-temperature and high-temperature ignition delay while dilution on oxygen mass fraction primarily affects and prolongs the high-temperature ignition delay. Nitric oxide (NO) significantly decreases the ignition delay compared to other exhaust gas compositions, with the high-temperature ignition delay experiencing a substantial decrease of 33.33% under 500 ppm NO addition at the ambient temperature of 820K. With the NO addition in the fresh intake air, conversion reactions occur between NO and nitrogen dioxide, and the reactions of NO with hydroperoxyl (HO2) and nitrogen dioxide with hydrogen radical lead to the generation of hydroxyl radical throughout the low- and high-temperature ignition stages, which enhances system reactivity and contributes to a decrease of ignition delay. The decrease in the oxygen mass fraction significantly reduces the rate of production of HO2 and hydrogen peroxide, which results in a decrease in the rate of production of hydrogen peroxide decomposition and HO2 deoxidation into hydroxyl radicals, prolonging the high-temperature ignition. The revealed mechanism may be applicable to the diagnosis of exhaust gas residual fault phenomenon.

Engineering rare earth metal Ce-N coordination as catalyst for high redox kinetics in lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries are a key area of research in energy storage due to their high theoretical energy density, low cost, and environmental friendliness. However, the shuttle effect caused by lithium polysulfides (LiPSs) intermediates often results in poor cycling stability. Therefore, constructing rational cathode structures to achieve fast reaction kinetics in adsorbing and catalyzing LiPSs is the key to obtain high-performance Li-S batteries. Metallic single-atom catalysts (SACs), known for their 100 % atomic utilization rate and low cost, have demonstrated excellent catalytic activity and selectivity in the redox reactions of Li-S batteries, positioning them as one of the most promising catalysts in this field. Rare earth metallic SACs with versatile oxidation states, diverse coordination chemistry and environmentally friendly are rarely investigated in Li-S system. Herein, we fabricate a rare earth metal-based single-atom catalyst (CeSAs) supported on a three-dimensional porous N-doped carbon (3DCeSA-N-WS), and systematically study its performance in Li-S batteries. Benefitting from the atomic dispersion and versatile oxidation states (Ce3+/Ce4+), the 3DCeSA-N-WS demonstrates excellent performance in anchoring and catalyzing LiPSs, significantly enhancing the redox reaction kinetics. Consequently, the prepared sulfur cathode exhibits exceptional electrochemical performance, with a high initial specific discharge capacity of 1225 mAh g−1 at 0.2 C and a capacity retention of 76.1 % after 160 cycles. The assembled 100 mAh-level pouch cellmaintains a high specific discharge capacity of 877 mAh g−1 after 50 cycles at 0.5 C. This work provides new insights into the design of sulfur cathode catalysts, thereby contributing to the realization of high-performance Li-S batteries.

High‐performance Porous Electrodes for Flow Batteries: Improvements of Specific Surface Areas and Reaction Kinetics

AbstractElectrodes, which offer sites for mass transfer and redox reactions, play a crucial role in determining the energy efficiencies and power densities of redox flow batteries. This review focuses on various approaches to enhancing electrode performance, particularly the methods of surface etching and catalyst deposition, as well as some other advanced strategies for regulating electrode surface properties. These approaches aim to increase active sites and enhance kinetics for the redox reactions, which are crucial for elevating power density and electrolyte utilization, eventually determining the performance of the flow battery. Highlighting the need for interdisciplinary research, this mini‐review suggests that future advancements in electrode design will significantly impact the commercial viability and adoption of redox flow batteries in sustainable energy storage solutions.

A Strategy for Modeling Nonstatistical Reactivity Effects: Combining Chemical Activation Estimates with a Vibrational Relaxation Model.

The kinetics of many chemical reactions can be readily explained with a statistical approach, for example, using a form of transition state theory and comparing calculated Gibbs energies along the reaction coordinate(s). However, there are cases where this approach fails, notably when the vibrational relaxation of the molecule to its statistical equilibrium occurs on the same time scale as the reaction dynamics, whether it is caused by slow relaxation, a fast reaction, or both. These nonstatistical phenomena are then often explored computationally using (quasi)classical ab initio molecular dynamics by calculating a large number of trajectories while being prone to issues such as zero-point energy leakage. On the other side of the field, we see resource-intensive quantum dynamics simulations, which significantly limit the size of explorable systems. We find that using a Fermi's golden rule type of model for vibrational relaxation, based on anharmonic coupling constants, we can extract the same qualitative information while giving insights into how to enhance (or destroy) the bottlenecks causing the phenomena. We present this model as a middle ground for exploring complex nonstatistical behavior, capable of treating medium-sized organic molecules or biologically relevant fragments. We also cover the challenges involved, in particular quantifying the excess energy in terms of vibrational modes. Relying on readily available electronic structure methods and providing results in a simple master equation form, this model shows promise as a screening tool for opportunities in mode-selective chemistry without external control.