Synthesis Parameters Research Articles

A review on Fe2O3‐based catalysts for toluene oxidation: catalysts design and optimization with the formation of abundant oxygen vacancies

Volatile organic compounds (VOCs) are typical pollutants with hazards for humans and the environment, and can be efficiently mitigated by catalytic combustion. Fe2O3‐based catalysts are a promising choice due to their low cost and strong redox ability. Several attempts have been made to promote the catalytic performance of Fe2O3 at low temperatures. This review summarizes the research progress on Fe2O3‐based catalysts for the oxidation of toluene, one of the most common and harmful VOC. Firstly, the properties and catalytical performance for Fe2O3‐based catalysts were summarized, and the reaction mechanisms for toluene oxidation on the surface of Fe2O3 were detailed to comprehend the role of oxygen vacancy. Then, the modification for single Fe2O3 catalysts, including synthesis parameters, structure and morphology control, has been introduced to reveal the correlation between physicochemical properties of catalysts and their activity. In addition, composite Fe2O3 catalysts, which can promote catalytic performance significantly due to the synergetic effect between different components, were comprehended. Finally, waste‐derived Fe2O3 catalysts with sustainable merit as converting waste into worth have been discussed. Moreover, the advanced machine learning tools, which are helpful in accelerating catalyst design, configuration optimization and reactivity prediction, have been introduced as an emerging research opportunity for the future.

Humidity Diode Sensors Based on 1D Nanosized Silicon Structures

Introduction. Humidity measurement is essential in microelectronics, aerospace, biomedical, and food industries, as well as in households for climate control. Currently, various types of devices have been used as humidity sensors: capacitive, resistive, diode, gravimetric, optical structures, field-effect transistors and devices based on surface acoustic waves.Problem Statement. Today, there is a need to develop IC-compatible humidity sensors that have high sensitivityand low cost. To this end, silicon nanowires have been successfully used in resistive and capacitive humidity sensors. However, there is a lack of research on the nanowire effect on device parameters of diode-type humidity sensors.Purpose. To develop diode sensors based on silicon nanowires and to determine the effect of process parameters of synthesis and structural features of nanowires on the performance of humidity sensors.Materials and Methods. The process of sensor fabrication includes several steps: chemical cleaning of silicon wafer, synthesis of silicon nanowires using standard or modified metal-assisted chemical etching, phosphorus diffusion to create a p-n junction, front and back metallization. The surface morphology of the nanostructures has been studied by scanning electron microscopy. The humidity-sensitive characteristics have been studied with theuse of salt hygrostats.Results. It has been shown that the addition of one-dimensional silicon nanostructures to the diode-type sensor signifi cantly improves its characteristics. The rectification ratio increases from 161 to 1807, the response ups from 4.5 to 25, the sensitivity grows from 1.6 to 4.02 (%RH)–1, while the response time and recovery time are reduced from 85/90 to 25/30 s, the hysteresis value goes down from 75 to 16%, the signal deviation after cycling drops from 15to 3%, and the signal fluctuation during continuous device operation decreases from 17 to 15%.Conclusions. The results have shown that the use of a simple and cheap nanowire synthesis technology is effective to produce humidity sensors.

Extracellular synthesis of heteroatom doped copper oxide nanoparticles from electronic waste – Transforming waste to resource for the remediation of nitrophenol contaminated water

Industrial effluents containing hazardous phenolic compounds such as 4-nitrophenol (4-NP) can threaten aquatic ecosystems and the environment. To address the environmental issues due to nitrophenol-contaminated industrial effluents and rapidly generating electronic waste (e-waste), catalytic nanoparticles are biosynthesized utilizing the waste printed circuit boards (WPCBs) and the cell-free supernatant (CFS) of the bacteria Alcaligenes aquatilis for the catalytic reduction of 4-NP with sodium borohydride (NaBH4). The optimum synthesis parameters to maximize 4-NP reduction were an initial pH of 12.4 and a volume ratio of metal leachate to CFS of 1:3. These nanoparticles were found to be heteroatom-doped CuO/Cu2O (Bio-CuO/Cu2O-PCB) with spherical shape, average crystallite size of 19 nm and average particle size of 19.2 nm. The biosynthesized nanoparticles exhibited excellent catalytic activity in the reduction of 4-NP with a pseudo-first-order rate constant (kapp) of 0.526 min-1, induction period of 2 min, and 90% reduction of 4-NP in 6 min. This work demonstrates the recovery of metal resources from waste as nanoparticles with excellent catalytic activity using a green, eco-friendly synthesis method under ambient conditions. Bio-CuO/Cu2O-PCB showed better activity than commercial CuO, biosynthesized and chemically synthesized CuO using precursor salt. The developed synthesis method is eco-friendly and could yield a recyclable catalyst for reducing harmful aromatic pollutants such as 4-NP present in wastewater to 4-aminophenol, a pharmaceutical intermediate.

Degree of serum LDL cholesterol reduction by simvastatin and ezetimibe is dependent on baseline LDL cholesterol concentration but not on baseline values and changes of cholesterol synthesis and absorption parameters.

We questioned whether the baseline status of low-density lipoprotein cholesterol (LDL-C), cholesterol synthesis and absorption, and the changes in these parameters determine the change in serum LDL-C under statin or ezetimibe treatment or under combination treatment. 37 mildly hypercholesterolemic healthy male subjects were studied under placebo, simvastatin (20mg/d), ezetimibe (10mg/d), and combination treatment. We correlated the change of LDL-C (ΔLDL-C) under treatment with the placebo end values of LDL-C (baseline), whole-body cholesterol synthesis, and hepatic cholesterol synthesis (serum lathosterol to cholesterol ratio) as well as fractional absorption rate (FAR) of cholesterol and serum campesterol to cholesterol ratio. The change in serum LDL-C was also correlated with the changes in synthesis and absorption parameters. ΔLDL-C was highly negatively related to baseline LDL-C under ezetimibe (p<0.0001), simvastatin (p<0.0001), and combination treatment (p<0.0001). Under combination treatment, LDL-C lowering appears possible from baseline values of 10 mg/dL upwards, while ΔLDL-C was independent of the baseline value (-50 to -60%). ΔLDL-C was positively associated with placebo FAR under ezetimibe (p=0.0106) and combination treatment (p=0.0457). No associations were found between ΔLDL-C and baseline values for synthesis nor between ΔLDL-C and changes in synthesis and absorption surrogate markers. Under ezetimibe, simvastatin, and combination treatment, ΔLDL-C is predominantly dependent on the baseline LDL-C concentration. We hypothesize that the concentration gradient between serum LDL-C and hepatic cellular cholesterol determines the efficiency of serum LDL-C lowering. Combination treatment is the preferred treatment.

Letting Pulsars Sing: Sonification With Granular Synthesis

An astronomy sonification project has been initiated to create sound and music from the data of pulsars in space. Pulsars are formed when some stars burn out all of their fuel and emit electromagnetic radiation, which hits earth periodically as the pulsar rotates. Each pulsar has unique characteristics. The source of the data is the online Pulsar Catalog from the Australian National Telescope Facility. The first result is a stereo fixed media composition, From Orion to Cassiopeia, which reveals a sweep of much of the Milky Way, displaying audio for many of the known pulsars. Galactic longitude, rotation speed, pulse width, mean flux density, age, and distance are mapped to granular synthesis parameters. Sound event duration, amplitude, amount of reverberation, grain rate, grain duration, grain frequency, and panning are controlled by the data. The piece was created with the new SGRAN2() instrument in the RTcmix music programming language.

Prediction of hydrogel swelling states using machine learning methods

AbstractIn the field of material informatics, artificial neural networks (ANNs) contribute to the investigation of the processing‐structure‐properties‐performance relationship of materials. This inspires us to leverage the capabilities of ANNs to decode properties of hydrogels, thereby customizing these active materials for sensors or actuators. In the current work, we introduce an approach to predict discrete swelling states of temperature‐responsive hydrogels, especially PNIPAAm, based on their synthesis parameters, utilizing ANN models. To build the database, we analyze literature on temperature‐responsive hydrogels and compile essential synthesis parameters. The corresponding data points related to these synthesis parameters are then extracted. We propose different variants of ANN models and compare their accuracy on the acquired dataset. The selected model can predict the swelling states of hydrogel samples within the test dataset with relative prediction error of 0.11. This approach is applied to predict the expected properties. Subsequently, the hydrogels can be synthesized, and their properties can be experimentally verified. Our approach can be extended to other types of hydrogels and in the prediction of additional properties. The identified synthesis parameters serve as a valuable foundation for the expansion of the database with further literature resources. An enriched database will enhance the performance of the data‐driven model, thereby improving its predictive capabilities.

Pure Tunable Emissions from Cesium Manganese Bromide by Monitoring the Crystal Fields Through a Sustainable Approach

AbstractResearch on manganese (Mn) halide perovskite derivatives with tunable emissions and high color purity have gathered a significant amount of attention for display technology. Despite of mesmerizing optical properties, the synthesis of these all‐inorganic Mn halide compounds is followed by complex and toxic processes. Second, a precise control over the synthesis parameters is mandatory to achieve their pure emissions. Therefore, an ecologically sustainable water‐based solution approach is adapted here to tailor the phases and emissions of cesium manganese bromide (Cs‐Mn‐Br) perovskite derivatives. It is observed that a controlled injection of solution stabilizer plays a pivotal role in engineering the intrinsic properties of Mn halide perovskites. This solution stabilizer interacts with the Mn‐ions of those perovskite derivatives influencing their surrounding coordination environment and pure emission from then. A pure green emission with PLQY of 82% is achieved from as prepared Cs3MnBr5, whereas CsMnBr3 showed a red emission with PLQY of ≈20%. Encouraged by these properties phosphor‐driven light emitting diodes (LED) are designed that show a steady electroluminescence intensity. The CIE coordinates of the Cs3MnBr5 and CsMnBr3 LED prototypes are at (0.224, 0.659) and (0.688, 0.316). This study showcases simple, eco‐friendly tactics for developing green and red LED prototypes contributing toward sustainable device design.

Design of Experiments for Optimized Synthesis of Carbon‐Supported Ni Nanoparticles: A Green Chemistry Approach

AbstractMetallic nickel nanoparticles supported on a high specific surface area carbon powder were synthesized by a classical polyol method without external reducing agent or surfactant. Ni/C materials were characterized by TGA, XRD, cyclic and linear voltammetry. To decrease the number of experiments, a Taguchi design of experiments (DoE) was implemented and the effects of different synthesis parameters (nature of the nickel salt, loading of Ni on carbon, nNaOH/nNi ratio and reaction time at reflux) on different responses (crystallite size, electrochemically active surface area and current density for the glucose oxidation reaction at 1.5 V) determined. Optimization of parameter values for decreasing the crystallite size down to 14 nm was achieved using the DoE. For the other responses, strong interactions between parameters avoided straightforward optimization of parameter values. However, some trends could be drawn from the experimental matrix showing that the synthesis of a catalyst loaded with only 10 wt% Ni, with NiCl2 as precursor salt, with a nNaOH/nNi ratio of 6 for 80 minutes at reflux was a good compromise between atom, time and energy savings, costs efficiencies, and electrochemically active surface area and catalytic activity towards the glucose oxidation reaction, particularly in terms of mass activity.

Influence of grain size on the electrochemical performance of Li7‑3xLa3Zr2AlxO12 solid electrolyte

Contemporary Li‐ion batteries are facing substantial challenges like safety and limited energy density. The development of all‐solid‐state battery cells mitigates safety hazards and allows the use of Li‐metal anodes increasing energy density. Garnet‐type solid electrolytes can be vital to achieving an all‐solid‐state cell and an understanding of the influence of its microstructure on the electrochemical performance is crucial for material and cell design. In this work the influence of grain size on the Li‐ion conductivity of Li7‐3xLa3Zr2AlxO12 (x = 0.22) is presented. The synthesis and processing procedure allows changing the ceramic grain size, while maintaining the same synthesis parameters, eliminating influences of the synthesis on grain boundary composition. Field assisted sintering technology is a powerful method to obtain dense, fine‐grained ceramics with an optimal grain size of 2‐3 µm, where the conductivity is double that of the counterpart (0.7 µm). A total Li‐ion conductivity of 0.43 mS cm‑1 and an activation energy of 0.36 eV were achieved. The oxide‐based all‐solid‐state battery cell combining the garnet‐type electrolyte, a Li‐metal anode and a thin‐film LiCoO2 cathode was assembled and cycled at room temperature for 90 hours. This represents a proof of concept, for the application of oxide‐based electrolytes at ambient temperatures.

Investigating the effects of synthesis parameter on textural and catalytic properties of ZnO-CuO-Al2O3-Cr2O3 mixed oxide in water gas shift reaction

The present study has investigated the influence of preparing conditions, including aging temperature and time, pH, and Tcalcination, on the co-precipitated ZnO-CuO-Al2O3-Cr2O3 mixed oxide at a high-temperature water gas shift reaction. XRD, BET, FTIR, TG-DTA, SEM, TEM, and H2-TPR were used to characterize the relationships between the synthesis parameters and the physicochemical features. The investigation proved that the activity in aging 5 h could be related to higher pore volume and lower crystalline size of 0.24 cm3g-1 and 6.4nm, respectively. Also found that increasing the aging temperature to 60°C results in a rise in the surface area and particle size of less than 6nm, enhancing the catalyst activity. The findings showed that raising the Tcalcination reduced the surface area from 132 to 65m2 g-1. It has been concluded that the CO conversion of 70% was obtained at a pH of 10 when aged at 60°C for 5 hours and calcination temperature of 400°C.

Multiparameter optimization of non-thermal plasma-driven synthesis of carbohydrate-stabilized rhenium nanoparticles towards enhancement of their catalytical activity for reduction of nitroaromatic compounds

This study aims to optimize the synthesis of carbohydrate-stabilized rhenium nanoparticles (ReNPs) utilizing cold atmospheric pressure plasma (CAPP), specifically direct current atmospheric pressure glow discharge (dc-APGD), hypothesizing that controlling synthesis parameters will enhance catalytic efficiency in the reduction of nitroaromatic compounds (NACs). The dc-APGD system operated in flowing liquid cathode (FLC-dc-APGD) and flowing liquid anode (FLA-dc-APGD) modes. Design of experiments (DOE) and response surface methodology (RSM) were employed for the first time to optimize ReNPs synthesis. This included optimizing the concentration of ReO4- in ReNPs precursor solution, solution flow rate as well as discharge current. ReNPs were characterized using high-resolution transmission electron microscopy (HRTEM), dynamic light scattering (DLS), and X-Ray photoelectron spectroscopy (XPS). In turn, optical emission spectroscopy (OES) was employed for the identification of reactive species generated in plasma phase that contributed to the synthesis of ReNPs. The resultant sizes, surface charges, and phase compositions were linked with synthesis parameters and then with catalytic activities revealed by the variety of ReNPs. HRTEM photomicrographs revealed spherical and spherical-like morphologies of obtained ReNPs synthesized using FLC-dc-dc-APGD and FLA-dc-APGD modes with the actual sizes of 7.28 ± 2.90nm and 3.24 ± 0.57nm, respectively. Optimized conditions yielded ReNPs with exceptional catalytic activity, reducing 94.9% (FLC-dc-APGD) and 90.5% (FLA-dc-APGD) of 4-nitrophenol (4-NP) with the apparent rate constants (k1) 0.269 and 0.107min-1, respectively. Further, the conversions of 90% were achieved over FLC-dc-APGD-based ReNPs for nitrobenzene (NB), 2,4,6-trinitrophenol (2,4,6-TNP), 2,4-dinitrophenol (2,4-DNP), and 4-nitroaniline (4-NA). In these cases, the k1 values were 0.235, 0.174, 0.070, 0.001min-1 for, respectively. The results allowed to find a correlation between ReNP size distribution, oxidation state, and catalytic activity that suggested a potential for tailored Re nanocatalysts in environmental remediation.

Influence of Chromium Carbide-Derived Carbon Support and Ceria Nanocrystals on Pt-CeO2/C Catalysts for Fuel Cell Applications

Abstract The influence of different synthesis parameters on CeO2 and Pt nanoparticle (NP) deposition on Ketjenblack carbon (C(KB)) was examined. The Pt NP diameter (3.1–4.1 nm) was not influenced by CeO2 synthesis parameters. The CeO2 NPs synthesized using ultrasound sonication contribute to a better durability of the Pt-CeO2/C against CO poisoning. In contrast, CeO2 synthesized using the microwave heating method contributes to better methanol oxidation reaction (MOR) activity at low potential. Synthesis parameters of CeO2 and Pt NPs developed for the C(KB)-based catalysts were applied for C(Cr3C2)-based catalysts. The Pt NP diameter of C(Cr3C2)-based catalysts was slightly higher (7.2 nm) as some Pt NPs were agglomerated. The C(Cr3C2) support facilitates the MOR and CO stripping, especially in the case of the Pt/C on C(Cr3C2) support. The MOR activity at 0.85 V of Pt/C on the C(Cr3C2) support is as good as the MOR activity for the best Pt-CeO2/C on the C(KB) support. The C(Cr3C2) support also improves the CO removal from the Pt surface. All the synthesized catalysts had better MOR activity than the commercial Pt/C(Vulcan) catalyst. The oxygen reduction reaction activity of Pt-CeO2/C catalysts with higher CeO2 content synthesized with the microwave heating method was very good.

Sustainable upgrading of crude glycerol via ultrasound-reinforced bio-refinery process with oxygen–nitrogen subsistence: Co-application of reusable heterogeneous catalyst

Selective/rapid production of value-added glyceryl triacetate (GT) from catalytic transformation of crude glycerol (CG) derived from biodiesel production procedure was systematically investigated using ultrasound-reinforced bio-refinery process with environmental friendliness. Interestingly, the tartaric-magnetic mesoporous alumina (TMMA) was synthesized via hydrothermal aluminization, calcination and functionalization, further applied as an active catalyst for CG acetylation under nitrogen and/or oxygen subsistence. The operative parameters for selective synthesis of GT derived optimization process were in the sequence of TMMA loading amount > ultrasonic level > acetylation time. The GT selectivity and activation energy derived from catalytic acetylation of CG using ultrasonic system were 97.78 % and 44.38 kJ/mol while traditional system were 52.51 % and 60.66 kJ/mol. For catalytic comparison, TMMA catalyst presented better turnover rate of CG transformation than that of marketable catalysts. Moreover, TMMA catalyst could be reused for 15 cycles without notable changing in physicochemical properties such as surface area and acidity which was contributed under oxygen subsistence by oxidative degradation, leading to long-term durability of catalytic performance and long-term repression of polymeric formation. The sustainable application of O2 molecular could perfectly restrain hard polymeric deposition on TMMA structure, leading to facile separation after complete acetylation. This work anticipated that specific integration between TMMA with CG acetylation can be further co-applied for practical process of biodiesel production using ultrasound-reinforced bio-refinery process.

Improvement of Hydrogen Peroxide and Glucose Detection in Serum using Persistent Luminescent Nanoparticles: Impact of Synthesis Parameters and Particle Size

In this study, we report the preparation of a library of nanoparticles doped with chromium (ZGO) through two distinct syntheses conducted at 120°C for 12 hours or 24 hours, followed by a calcination at 500°C or 750°C. Using centrifugation, and starting from polydisperse samples, we demonstrated the ability to achieve different sizes in a monodisperse manner. Furthermore, our research revealed that ZGO react differently with hydrogen peroxide (H2O2) based on their size, synthesis duration, and calcination temperature. We observed the most significant amplification of persistent luminescence for particles prepared at 120°C for 12 hours and calcinated at 500°C, with a size of 100 nm, in the presence of 100 mM H2O2. This study enabled the detection of H2O2 in serum, with a detection limit of up to 2.1 µM. Additionally, we designed a glucose test for based on the responsiveness of ZGO PLNPs to H2O2. Using glucose oxidase, the glucose detection limit in serum was established around 0.13 µM, with a detection range between 0 ‐ 5 µM. These findings could open new avenues to further control the size, synthesis, calcination temperature, and persistent luminescence of PLNPs, thus enhancing their utility in the development of new in vitro biosensors.

Tailoring Microemulsification Techniques for the Encapsulation of Diverse Cargo: A Systematic Analysis of Poly (Urea-Formaldehyde) Microcapsules

Cargo encapsulation through emulsion-based methods has been pondered over the years. Although several microemulsification techniques have been employed for the microcapsule’s synthesis, there are still no clear guidelines regarding the suitability of one technique over the others or the impacts on the morphological and physicochemical stability of the final particles. Therefore, in this systematic study, we investigated the influence of synthesis parameters on the fabrication of emulsion-based microcapsules concerning morphological and physicochemical properties. Using poly(urea-formaldehyde) (PUF) microcapsules as a model system, and after determining the optimal core/shell ratio, we tested three different microemulsification techniques (magnetic stirring, ultrasonication, and mechanical stirring) and two different cargo types (100% TEGDMA (Triethylene glycol dimethacrylate) and 80% TEGDMA + 20% DMAM (N,N-Dimethylacrylamide)). The resulting microcapsules were characterized via optical and scanning electron microscopies, followed by size distribution analysis. The encapsulation efficiency was obtained through the extraction method, and the percentage reaction yield was calculated. Physicochemical properties were assessed by incubating the microcapsules under different osmotic pressures for 1 day and 1, 2, or 4 weeks. The data were analyzed statistically with one-way ANOVA and Tukey’s tests (α = 0.05). Overall, the mechanical stirring resulted in the most homogeneous and stable microcapsules, with an increased reaction yield from 100% to 50% in comparison with ultrasonication and magnetic methods, respectively. The average microcapsule diameter ranged from 5 to 450 µm, with the smallest ones in the ultrasonication and the largest ones in the magnetic stirring groups. The water affinities of the encapsulated cargo influenced the microcapsule formation and stability, with the incorporation of DMAM leading to more homogeneous and stable microcapsules. Environmental osmotic pressure led to cargo loss or the selective swelling of the shells. In summary, this systematic investigation provides insights and highlights commonly overlooked factors that can influence microcapsule fabrication and guide the choice based on a diligent analysis of therapeutic niche requirements.

Using solid waste to treat wastewater: Preparation of flowerlike calcium silicate hydrate from coal fly ash for cadmium removal

Efficient utilization of Coal fly ash (CFA) and ingenious treatment of cadmium (Cd (II)) in the water environment are interesting topics. In this paper, a mesoporous floral calcium silicate hydrate (MCSH) for removal of Cd (II) was prepared by low temperature hydrothermal synthesis using CFA desilication solution. Different synthesis parameters (molar ratio of Ca to Si (Ca/Si), temperature, time) of MCSH were investigated and optimized. All synthesized MCSH showed good adsorption properties for Cd (II), and MCSH synthesized at Ca/Si molar ratio of 1.0, temperature of 363 K and time of 120 min had the optimum Cd (II) adsorption capacity of 357.43 mg/g. The effects of solution pH, MCSH dosage, coexisting cations and ionic strength on the Cd (II) adsorption performance by MCSH were further considered systematically. The adsorption process was a spontaneous and endothermic process, conformed to the pseudo-second-order kinetic and Langmuir isothermal model. The main mechanism of Cd (II) removal by MCSH was the precipitation between Cd (II) and OH– released by MCSH, accompanied by ion exchange, surface complexation and electrostatic adsorption. The mesoporous flowery MCSH prepared from CFA provides an satisfactory solution for the utilization of solid waste resources and the purification of heavy metal wastewater.

Exploring the impact of annealing temperature on morphological, structural, vibrational and electron paramagnetic resonance properties of starch-mediated spinel CoAl2O4: Experimental and DFT study

In the present work, CoAl2O4 nanoparticles were successfully synthesized using the simple auto-combustion sol-gel method employing starch as an organic fuel source. The effect of the annealing temperature on the structural, vibrational, morphological, and magnetic properties is studied. The obtained spherical nanoparticles have grain sizes ranging from 23.54 nm to 46.50 nm. X-ray diffraction (XRD) patterns reveal the formation of a face centered cubic (fcc) spinel phase with the Fd-3m space group for all prepared samples. The calculated average crystallite sizes exhibit an increase from 24.65 nm to 56.27 nm, consistent with the observed grain sizes. Density Functional Theory (DFT) calculations are applied to reach the optimized cell parameters as well as to confirm the structural properties of the synthetized CoAl2O4 nanoparticles. Geometry optimization of the CoAl2O4 spinel oxide is performed using the CASTEP module of Materials Studio software. The optimized unit cell, lattice parameter and unit cell volume were obtained from this simulation. The combined experimental and density functional theory study of structural properties of CoAl2O4 revealed that an increase in the calcination temperature leads to an increase in the volume of the unit cell and hence to an increase in the particles size. Fourier-transform infrared spectroscopy (FTIR) further corroborated these findings by demonstrating subtle shifts in characteristic CoAl2O4 absorption peaks with varying annealing temperatures. These peak shifts suggest a potential redistribution of Al³⁺ and Co2⁺ ions between tetrahedral and octahedral sites within the spinel structure. Electron paramagnetic resonance (EPR) spectroscopy revealed a magnetic state transition as a function of both the annealing temperature and the resulting crystallite size. Occupancy fluctuations of Al³⁺ and Co2⁺ ions at specific sites have also impacted on the nanoparticles color since the hue of the material depends on the valence state and the cationic coordination environment in the CoAl2O4 crystal lattice. Correlations between structural, vibrational, magnetic and color properties are presented to understanding how synthesis parameters influence CoAl2O4 characteristics which is essential for tailoring materials for specific applications.

Manufacturing Free‐Standing, Porous Metallic Layers with Dynamic Hydrogen Bubble Templating

AbstractThe 3D structure (i.e., microstructure) of porous electrodes governs the performance of emerging electrochemical technologies such as fuel cells, electrolysis, and batteries. Sustaining electrochemical reactions and convective‐diffusive mass transport at high efficiency is complex and motivates the search for sophisticated microstructures with multimodal pore size distributions and pore size gradients. Here a new synthesis route for porous, metallic layers is presented that combines the characteristics of carbon structures (i.e., pore size, porosity) with the properties of metals (i.e., recyclability, conductivity). Building on the method of dynamic hydrogen bubble templating, a novel approach is engineered to manufacture thin, free‐standing layers using an electrochemical flow cell through the introduction of an intermediate layer and optimization of the synthesis parameters. Mechanically stable layers are created with thicknesses ranging from ≈50 to ≈200 µm comprising porous, dendritic structures, arranged to form a vascular network of larger pores with a gradient in radii from ≈5 µm at the bottom and up to ≈36 µm at the top of the material. Using X‐ray tomographic data, the morphology is analyzed, and the diffusive transport through the material as a function of liquid filling is simulated and compared to state‐of‐the‐art carbon fiber‐based electrodes, showing significantly higher mass transfer properties.

Optimization of the synthesis parameters and analysis of characteristics of 1,1-diamino-2,2-dinitroethylene

2,2-Dinitroethene-1,1-diamine (FOX-7) is a low-sensitive explosive suitable for various energy-material applications. It can be synthesized based on the nitration and hydrolysis of heterocyclic precursors derived from 2-methylimidazole-4,5-dione (MID) or 2-methylpyrimidine-4,6-diol (MPD). However, more information about its optimal synthesis parameters during production from MPD as a starting material is needed. In this study, Taguchi's experimental design method was used to improve the yield of FOX-7. Verification of the results shows that the optimal synthesis parameters are as follows: the molar ratio of HNO3/MPD is 8, the reaction time is 180 minutes, and the reaction temperature is 15°C; the maximum yield of FOX-7 can reach 79.14%. Furthermore, the synthesized FOX-7 was identified and characterized by nuclear magnetic resonance (NMR) spectroscopy analysis, Fourier transforms infrared spectroscopy (FTIR), Raman spectroscopy analysis, and powder X-ray diffraction (PXRD).

CoFeBP Micro Flowers (MFs) for Highly Efficient Hydrogen Evolution Reaction and Oxygen Evolution Reaction Electrocatalysts.

Hydrogen is one of the most promising green energy alternatives due to its high gravimetric energy density, zero-carbon emissions, and other advantages. In this work, a CoFeBP micro-flower (MF) electrocatalyst is fabricated as an advanced water-splitting electrocatalyst by a hydrothermal approach for hydrogen production with the highly efficient hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The fabrication process of the CoFeBP MF electrocatalyst is systematically optimized by thorough investigations on various hydrothermal synthesis and post-annealing parameters. The best optimized CoFeBP MF electrode demonstrates HER/OER overpotentials of 20 mV and 219 mV at 20 mA/cm2. The CoFeBP MFs also exhibit a low 2-electrode (2-E) cell voltage of 1.60 V at 50 mA/cm2, which is comparable to the benchmark electrodes of Pt/C and RuO2. The CoFeBP MFs demonstrate excellent 2-E stability of over 100 h operation under harsh industrial operational conditions at 60 °C in 6 M KOH at a high current density of 1000 mA/cm2. The flower-like morphology can offer a largely increased electrochemical active surface area (ECSA), and systematic post-annealing can lead to improved crystallinity in CoFeBP MFs.