Concurrent Decomposition Research Articles

Revisiting Li-CO2/O2 battery chemistry through the spatial distributions of discharge products and their oxidation behaviors

Li-CO2/O2 batteries present a promising strategy for CO2 conversion and energy storage, yet the complexity of discharge products poses challenges for revealing their oxidation. Here, we simulate the influences of various properties of Li2CO3 and/or Li2O2 on the decomposition pathway by comprehensively analyzing the singlet O2 (1O2) and gas components (O2 and CO2) generated during electrochemical oxidation. Our results show that no matter Li2CO3 or Li2O2, the decomposition of samples with small size and poor crystallinity produces less 1O2 and more gas product. Especially, small and poorly crystalline Li2CO3 triggers the concurrent decomposition of Li2CO3 and C, while large and highly crystalline Li2CO3 favors the solo decomposition pathway. Furthermore, the 1O2 yield can be most inhibited at a Li2CO3/Li2O2 ratio of 50 %. After clarifying the nature of Li2CO3 and/or Li2O2 oxidation, the spatial distributions of the oxygen discharge product in Li-CO2/O2 batteries were observed by scanning transmission X-ray microscopy (STXM). Li2CO3 is mainly distributed in the interior of large aggregates with high crystallinity. Poorly crystalline Li2O2 appears as small particles or coats on the surface of Li2CO3. Combined with multi-dimensional information of the discharge products and simulation results, the oxidation behaviors of the discharge products in Li-CO2/O2 batteries are reacquainted.

Sparse Multichannel Decomposition of Electrodermal Activity With Physiological Priors.

Goal: Inferring autonomous nervous system (ANS) activity is a challenging issue and has critical applications in stress regulation. Sweat secretions caused by ANS activity influence the electrical conductance of the skin. Therefore, the variations in skin conductance (SC) measurements reflect the sudomotor nerve activity (SMNA) and can be used to infer the underlying ANS activity. These variations are strongly correlated with emotional arousal as well as thermoregulation. However, accurately recovering ANS activity and the corresponding state-space system from a single channel signal is difficult due to artifacts introduced by measurement noise. To minimize the impact of noise on inferring ANS activity, we utilize multiple channels of SC data. Methods: We model skin conductance using a second-order differential equation incorporating a time-shifted sparse impulse train input in combination with independent cubic basis spline functions. Finally, we develop a block coordinate descent method for SC signal decomposition by employing a generalized cross-validation sparse recovery approach while including physiological priors. Results: We analyze the experimental data to validate the performance of the proposed algorithm. We demonstrate its capacity to recover the ANS activations, the underlying physiological system parameters, and both tonic and phasic components. Finally, we present an overview of the algorithm's comparative performance under varying conditions and configurations to substantiate its ability to accurately model ANS activity. Our results show that our algorithm performs better in terms of multiple metrics like noise performance, AUC score, the goodness of fit of reconstructed signal, and lower missing impulses compared with the single channel decomposition approach. Conclusion: In this study, we highlight the challenges and benefits of concurrent decomposition and deconvolution of multichannel SC signals.

Concurrent decomposition and replacement of marine gas hydrate with the injection of CO2-N2

• CO 2 -N 2 was injected into gas hydrate sediments under real reservoir conditions. • Concurrent CH 4 hydrate decomposition and CO 2 -N 2 replacement occurs distinctly. • Local non-equilibrium with a higher CH 4 concentration leads to a local replacement. • Both of decomposition and replacement contributes to gas recovery. • Dual production pattern combines advantages of depressurization and replacement. CO 2 replacement has been regarded as a promising method for the recovery of gas hydrate. The kinetics and feasibility of its application to gas hydrate reservoir are extensively studied at low temperatures that are proper for the formation of CO 2 /N 2 hydrates. However, in facts, most of the gas hydrate reservoirs in marine sediments have relatively high temperature conditions that are below the hydrate equilibrium line of CO 2 /N 2 . In this work, CO 2 -N 2 gas was injected into gas hydrate sediments under the pressure–temperature conditions of real marine hydrate reservoirs to evaluate the kinetic behavior of the CO 2 -N 2 replacement at relatively high temperatures. It was observed that the CH 4 production was more prominent than the sequestration of CO 2 -N 2 . The results indicate that concurrent decomposition and replacement occur distinctly in gas hydrate reservoir with relatively high temperatures after the injection of CO 2 -N 2 . It is proposed that the local non-equilibrium with a higher concentration of CH 4 near the dissociating hydrate surface than that of the bulk gas phase can lead to a local CO 2 -N 2 replacement. The contribution of decomposition and replacement to gas recovery varies with the temperature and pressure conditions. Higher temperature and lower pressure would promote the decomposition and inhibit replacement, enhancing the gas recovery efficiency. This dual production pattern combines the advantages of both depressurization and replacement, which would substantially improve the safety of depressurization method for weak hydrate reservoir conditions in efficient gas recovery as the geologic storage of CO 2 -N 2 in hydrate form consolidates the sediments. These findings extend the previous knowledge on CO 2 replacement method and provide insights for a complete understanding of the application of this method to the real marine gas hydrate reservoirs.

Mechanisms of genuine humic acid evolution and its dynamic interaction with methane production in anaerobic digestion processes

Humic acid (HA), a byproduct formed during the biological conversion of organic matter into biogas in the anaerobic digestion (AD) process, contains complex structures and redox functions. However, the evolution mechanism of HA and its interaction with CH4 production during the AD process have not been fully explored, particularly with respect to various substrates and temperature conditions. In this study, we investigated the evolutionary dynamics of the structure and function of genuine HA that naturally formed in the AD processes of chicken manure and corn stover under mesophilic (37 °C) and thermophilic (55 °C) conditions. The results demonstrated that the HA evolution mechanisms in AD of chicken manure and corn stover have different pathways. The AD of core stover showed higher degree of aromaticity (41.2–66.7% and 45.3–68.4% for mesophilic and thermophilic respectively) and humification index (1.5–4.2 and 2.8–4.5 for mesophilic and thermophilic respectively) than those (28.3–45.3% and 30.2–54.5% of aromaticity and 0.6–1.2 and 1.3–3.7 of humification index) in AD of chicken manure. The results from HSQC NMR spectroscopy and 2D-COS-FTIR spectroscopy demonstrated an accelerating effect of the higher temperature on the evolution of HA through humification. Moreover, the concurrent decomposition and re-polymerization of HA during both AD processes, resulting in positive and negative effects on CH4 production in the fast and slow CH4 production stages, respectively. The dynamic interaction was due to variations in the electron transferring ability and structure of the formed HA. The results could not only advance our understanding of the mechanisms of HA evolution and its interaction with the performance of AD process, but also support further research toward improving AD performance by regulating HA formation and transformation.

Systematic activation of potassium peroxydisulfate with ZIF-8 via sono-assisted catalytic process: Mechanism and ecotoxicological analysis

Abstract Powerful and suitable combination of different advanced oxidation processes (AOPs) has raised a new challenge in recent years. Since the generation of synergistic phenomenon is vital in the final integrated process, there is still an urgent demand for developing a superior hybrid AOPs, which is synergistically effective, simply and economically prepared and operated. Herein, a novel combination of ZIF-8 nanomaterials (NMs) and sonolysis process was utilised for efficient activation of potassium peroxydisulfate (PDS), leading to the establishment of a novel combined sono-assisted indirect photocatalytic process. ZIF-8 NMs were fabricated by a facial and green synthesis method at room temperature. The XRD, TEM, and BET analyses confirmed the successful production of porous ZIF-8 nanomaterials with sodalite (SOD) topology and hexagonal shapes including the specific surface area of 1484.28 m2/g. Besides, the effects of operational parameters including pH, ZIF-8, and PDS, Acid Blue 7 (AB7) concentration and ultrasonic bath power (UBP) were investigated on three response parameters consisting of AB7 removal efficiency (RE (%)), pseudo-first-order kinetic rate constant (kapp) and synergistic factor (SF). Optimum operating conditions were determined as pH = 5, [ZIF-8] = 0.6 g/L, [PDS] = 0.6 mmol/L in which maximum SF of 1.45 was achieved. The concurrent decomposition of S2O82−, HSO5−, H2O2, and AB7 on the active sites of ZIF-8 NMs were responsible for degradation. Based on the identified by-products via GC–MS technique, the AB7 sonocatalytic degradation mechanism was proposed. Finally, valuable efforts were made to assess the ecotoxicological effects of AB7, ZIF-8 NMs and the produced intermediates under optimised operating conditions. Sono-assisted indirect photocatalytic process in the presence of ZIF-8 NMs activated PDS can be noticed as an acceptable and green integrated process due to its high SF and novel features.

Unraveling the Impact of Ether and Carbonate Electrolytes on the Solid-Electrolyte Interface and the Electrochemical Performances of ZnSe@C Core-Shell Composites as Anodes of Lithium-Ion Batteries.

The recognition of the solid electrolyte interface (SEI) between the electrode materials and electrolyte is limiting the selection of electrode materials, electrolytes, and further the electrochemical performance of batteries. Herein, we report ZnSe@C core-shell nanocomposites derived from ZIF-8 as anode materials of lithium-ion batteries, the electrochemical performances, and SEI films formed on ZnSe@C in both ether and carbonate electrolytes. It is found that ZnSe@C delivers a reversible capacity of 617.1 mA h·g-1 after 800 cycles at 1 A·g-1 in the ether electrolyte, much higher than that in the carbonate electrolyte. Both ex situ X-ray diffraction and X-ray photoelectron spectroscopies reveal that stable SEI films are formed on ZnSe@C in the ether electrolyte while selenium is involved in the formation of SEI films and further dissolved into the carbonate electrolyte because of the concurrent decomposition of electrolytes and insertion of Li+ into ZnSe, which differentiates between the cycling performances of ZnSe@C composites in ether and carbonate electrolytes.

Solar photocatalysis mediated by ZnO for the removal of last traces of Indigo carmine dye pollutant from water

Solar photocatalysis as a potential green technology for the removal of traces of the dye pollutant Indigo carmine (IC) from water is investigated using ZnO as the catalyst. Degradation/decolorization alone does not result in complete decontamination as seen from the significant Chemical Oxygen Demand (COD) of water even after the parent compound has disappeared completely. The degradation proceeds through many intermediates which also get mineralized eventually but slowly. Oxalic acid is identified as a stable slow mineralizing degradation product which itself is formed from other transient intermediates. Effect of various parameters such as catalyst dosage, concentration of the dye, pH, temperature, presence of contaminant salts etc. on the degradation is investigated and quantified. Oxidants such as S2O82- and H2O2 have only moderate influence on the degradation. The degradation follows variable kinetics depending on the concentration of the substrate. The reaction proceeds very slowly in the absence of O2 indicating the importance of reactive oxygen species and hydroxyl free radicals in photocatalysis. H2O2 formed insitu in the system undergoes concurrent decomposition resulting in stabilization in its concentration. The study demonstrates that solar photocatalysis can be used as a viable tool for the purification of water contaminated with traces of IC.

Impact of supporting electrolytes on the stability of TiO2–Ti counter electrode during H2O2 electrogeneration

This work focuses on the role of common supporting electrolytes (SEs) in the electro-chemical inertness of Ti-based materials employed for the anodic (direct) oxidation coupled with H2O2 electro-generation at the graphite cathode for the concurrent decomposition of organic contaminants. SEs are added to boost up the ionic conductivity of solution but a question always remains on the effect of SEs on the stability of anode materials. The use of ClO 4 − is encouraged in the electro-Fenton process as it does not form complexes with Fe2+/Fe3+; however, it is found that ClO 4 − corroded the TiO2 coated Ti (TiO2–Ti) anode very fast (>60 min) and, Ti4+ ions formed a yellow color complex (λmax = 380 nm) with H2O2. The influence of Cl–, NO 3 − and SO 4 2− was insignificant on the stability of TiO2–Ti. The cell current efficiency of H2O2 formation dropped sharply with in the case of TiO2–Ti anode. The TiO2–Ti corrosion also reduced the mass transfer co-efficient of DO transport from bulk to the cathode surface because of Ti4+ adsorption on graphite.

Operando Nanobeam Diffraction to Follow the Decomposition of Individual Li2O2 Grains in a Nonaqueous Li-O2 Battery.

Intense interest in the Li-O2 battery system over the past 5 years has led to a much better understanding of the various chemical processes involved in the functioning of this battery system. However, detailed decomposition of the nanostructured Li2O2 product, held at least partially responsible for the limited reversibility and poor rate performance, is hard to measure operando under realistic electrochemical conditions. Here, we report operando nanobeam X-ray diffraction experiments that enable monitoring of the decomposition of individual Li2O2 grains in a working Li-O2 battery. Platelet-shaped crystallites with aspect ratios between 2.2 and 5.5 decompose preferentially via the more reactive (001) facets. The slow and concurrent decomposition of individual Li2O2 crystallites indicates that the Li2O2 decomposition rate limits the charge time of these Li-O2 batteries, highlighting the importance of using redox mediators in solution to charge Li-O2 batteries.

Application of solar energy in wastewater treatment: Photocatalytic degradation of α-methylstyrene in water in presence of ZnO

Zinc oxide mediated photocatalytic degradation of trace amounts of the petrochemical pollutant α-methylstyrene (AMS) in water is investigated using sunlight as the energy source. The influence of various parameters such as catalyst dosage, initial concentration of AMS, pH, insitu formed intermediates, humic acid, H2O2, O2 etc., on the rate of degradation is investigated. Acetophenone (ACP) is identified as the major intermediate in the degradation. Both AMS and ACP inhibit the degradation of one another, the extent of inhibition being dependent on the relative concentration of one with respect to the other. H2O2 formed in the process acts as a reservoir of various Reactive Oxygen Species (ROS) which can enhance the degradation. However, H2O2 also acts as a scavenger for the ROS leading to its own concurrent decomposition. The degradation of AMS follows first order kinetics. The degradation is slow in deaerated system thereby reconfirming the role of O2 in the photocatalytic process. The catalyst can be recycled at least three times repeatedly before there is reduction in activity. The study clearly shows that zinc oxide mediated solar photocatalysis can be used as an effective tool for the tertiary treatment of AMS contaminated water thus indicating its potential for achieving the twin objectives of solar energy harvesting and wastewater treatment.

Highly toughened dense TiC–Ni composite by in situ decomposition of (Ti,Ni)C solid solution

A highly-toughened TiC–Ni composite was produced by the in situ decomposition during sintering of a nonequilibrim (Ti,Ni)C solid-solution phase. The solid solution was synthesized by the mechanical milling of Ti–Ni alloy/graphite mixtures, which then decomposed to finely dispersed TiC and Ni upon heating in a vacuum. To take advantage of the fine microstructure, samples were sintered to facilitate the in situ decomposition. Densification of the (Ti,Ni)C during the sintering was achieved through the coalescence of fine particles and the concurrent decomposition of the nonequilibrium (Ti,Ni)C phase. Additional densification was obtained through liquid-phase sintering by the eutectic melting of Ni. The fracture toughness of the sintered TiC–Ni composite was notably higher than that of conventional TiC/Ti(CN)–Ni or of comparable Ti(CN)–WC–Ni composites. Its fine and dense microstructure is believed to account for the enhanced toughness. The method suggested here might represent a valuable option for the preparation of TiC–Ni composites with desirable mechanical properties.

Synthesis and Characterization of Nanostructured Nickel Diselenide NiSe2 from the Decomposition of Nickel Acetate, (CH3CO2)2Ni

Solution processed NiSe2 nanorods were synthesized by a modified colloidal synthesis technique, by chemical reaction of TOPSe and nickel acetate at 150°C. The rods exist as an oleic acid ligand stabilized solution, with oleic acid acting as a capping group. Structural characterization by X‐ray diffraction and transmission electron microscopy indicates that the particles are rod‐like shaped crystals with a high and relatively constant aspect ratio (30 : 1). TEM shows that the width and the length of the nanorods are in the range 10–20 nm and 300–350 nm, respectively. XRD indicates that the nanorods are pure and well crystallized. The size of nanorods based on the Debye‐Scherrer effect, was 150 nm, the average value of length and width. They display thermal stability over prolonged heating times (<100 hours) at 150°C, for which the average particle size is roughly constant. After about 100 hours of heating time there is an onset and growth of micron sized cubes and concurrent decomposition of NiSe2 to Ni and NiSe at 150°C.

Control of nitrogen insertion during the growth of nitrogen-containing carbon nanofibers on cordierite monolith walls

A well attached coating of nitrogen-functionalised carbon nanofibers (N-CNFs) has been prepared on the walls of cordierite monolith channels. It is formed via concurrent decomposition of ethane and ammonia catalysed by nickel nanoparticles dispersed on alumina coated cordierite monolith. N-CNF/monoliths synthesis employing several growth temperatures and NH(3) compositions was exhaustively characterised by Raman, XPS, elemental analysis and TEM. Synthesis conditions affected profoundly content and type of nitrogen functionality, enabling its fine tuning. N-CNFs surface chemistry and microstructure differed remarkably from its N-free counterparts.

Ethanol Dehydration to Ethylene in a Stratified Autothermal Millisecond Reactor

The concurrent decomposition and deoxygenation of ethanol was accomplished in a stratified reactor with 50-80 ms contact times. The stratified reactor comprised an upstream oxidation zone that contained Pt-coated Al(2)O(3) beads and a downstream dehydration zone consisting of H-ZSM-5 zeolite films deposited on Al(2)O(3) monoliths. Ethanol conversion, product selectivity, and reactor temperature profiles were measured for a range of fuel:oxygen ratios for two autothermal reactor configurations using two different sacrificial fuel mixtures: a parallel hydrogen-ethanol feed system and a series methane-ethanol feed system. Increasing the amount of oxygen relative to the fuel resulted in a monotonic increase in ethanol conversion in both reaction zones. The majority of the converted carbon was in the form of ethylene, where the ethanol carbon-carbon bonds stayed intact while the oxygen was removed. Over 90% yield of ethylene was achieved by using methane as a sacrificial fuel. These results demonstrate that noble metals can be successfully paired with zeolites to create a stratified autothermal reactor capable of removing oxygen from biomass model compounds in a compact, continuous flow system that can be configured to have multiple feed inputs, depending on process restrictions.

A new technology for the production of isoprene from isobutene-containing C4 fractions and formaldehyde: Prospects for industrial reconstruction

The industrially implemented process of isoprene production from isobutene-containing C4 fractions and formaldehyde, which includes the gas-phase high-temperature decomposition of an intermediate, 4,4-dimethyl-1,3-dioxane, is expensive and obsolete. We propose a new technology that requires the same precursors and allows for a reduction in the cost of isoprene by a factor of at least 1.5. It features the concurrent liquid-phase decomposition of intermediate products in a column reactor in the presence of an aqueous solution of phosphoric acid at a moderate temperature (∼160°C), and is convenient for reconstructing existing production lines.

STRUCTURE, CHARACTERIZATION AND APPLICATION OF NI HYDROTALCITE AS SOLID BASE CATALYSTS FOR ORGANIC TRANSFORMATIONS

Ni hydrotalcites with different kinds of metals, ions exhibit considerable activity for organic transformations. Various ratios of Ni-Al hydrotalcites are prepared by using different compositions are characterized by XRD, IR and TPR analysis. Carbonate in the brucite sheets is active for selective oxidation reactions. Upon calcination the dehydroxylation of the hydrotalcite and concurrent decomposition of the carbonate ions produce mixed oxides which exhibits activity for variety of organic transformations.

Coordination by design and the price of autonomy

We consider a multi-agent planning problem as a set of activities that has to be planned by several autonomous agents. In general, due to the possible dependencies between the agents’ activities or interactions during execution of those activities, allowing agents to plan individually may lead to a very inefficient or even infeasible solution to the multi-agent planning problem. This is exactly where plan coordination methods come into play. In this paper, we aim at the development of coordination by design techniques that (i) let each agent construct its plan completely independent of the others while (ii) guaranteeing that the joint combination of their plans always is coordinated. The contribution of this paper is twofold. Firstly, instead of focusing only on the feasibility of the resulting plans, we will investigate the additional costs incurred by the coordination by design method, that means, we propose to take into account the price of autonomy: the ratio of the costs of a solution obtained by coordinating selfish agents versus the costs of an optimal solution. Secondly, we will point out that in general there exist at least two ways to achieve coordination by design: one called concurrent decomposition and the other sequential decomposition. We will briefly discuss the applicability of these two methods, and then illustrate them with two specific coordination problems: coordinating tasks and coordinating resource usage. We also investigate some aspects of the price of autonomy of these two coordination methods.

Thermochemical Study of Photoinduced Processes at TiO2 Nanoparticles in Aqueous Suspension Containing Br- or Cl-. Photodeaggregation and Subsequent Processes

Laser pulse-induced optoacoustic calorimetry (LIOAC) was applied to determine enthalpy changes in aerated aqueous suspensions of TiO2 nanoparticles (2.4 nm mean diameter) at pH = 1 in the absence and presence of the halide ions X- = Br- or Cl-. LIOAC demonstrates that in the system TiO2|H2O, O2 10% of the absorbed optical energy are stored for at least a few μs, which can be assigned to the decomposition of water. In the systems containing the X-, the overall photoprocess was exothermic although the oxidation of X- to - and the concurrent decomposition of water are endothermic. As an explanation we suggest a model in which the photodeaggregation of TiO2 nanoparticle aggregates produces additional photocatalyst surface area. The subsequent establishment of the thermodynamic equilibria on the additional surface comprises protonation of the TiO2 particles, halide adsorption, and formation of the electrochemical double layer. All these processes are exothermic. Adsorption of X- is best described by a Temkin-isotherm with in the range −5 to −20 kJ mol-1 for the transfer of X- from the outer to the inner Helmholtz plane on the TiO2 particles. The enthalpy of deaggregation is ca. + 30 kJ mol-1 as was calculated on the basis of energy conservation considerations.

IMPROVING SUPERVISED LEARNING BY SAMPLE DECOMPOSITION

This paper introduces a new ensemble technique, cluster-based concurrent decomposition (CBCD) that induces an ensemble of classifiers by decomposing the training set into mutually exclusive sub-samples of equal-size. The CBCD algorithm first clusters the instance space by using the K-means clustering algorithm. Afterwards it produces disjoint sub-samples using the clusters in such a way that each sub-sample is comprised of tuples from all clusters and hence represents the entire dataset. An induction algorithm is applied in turn to each subset, followed by a voting mechanism that combines the classifier's predictions. The CBCD algorithm has two tuning parameters: the number of clusters and the number of subsets to create. Using a suitable meta-learning it is possible to tune these parameters properly. In the experimental study we conducted, the CBCD algorithm, using an embedded C4.5 algorithm, outperformed the bagging algorithm of the same computational complexity.

Influence of Ni content on physico-chemical characteristics of Ni, Mg, Al-Hydrotalcite like compounds

The physico-chemical properties of a series of Ni,Mg,Al-HTLC with Al/(Al+Mg+Ni) = 0.25 and low Ni/Mg ratios were studied by means of X-ray diffraction (XRD), thermogravimetric (TGA) and thermodifferential (DTA) analysis, N2 physissorption and temperature programmed reduction (TPR). The as-synthesized materials were well-crystallized, with XRD patterns typical of the HTLCs in carbonate form. Upon calcination and dehydration the dehydroxilation of the layers with concurrent decomposition of carbonate anions produced mixed oxides with high surface area. XRD analysis indicated that the different nickel and aluminum oxides species are well-dispersed in a poor-crystallized MgO periclase-type phase. As observed by TPR, the different Ni species showed distinct interactions with Mg(Al)O phase, which were influenced by both nickel content and calcination temperature. Regardless of the the nickel content, the reduction of nickel species was not complete as indicated by the presence of metallic dispersions.