Optimization Of Synthesis Parameters Research Articles

Synthesis and characterization of C@CdS core-shell structures for high-performance capacitors

The present study investigates the synthesis and characterization of carbon@cadium sulphide (C@CdS) core-shell nanostructures for their potential application in electrochemical double-layer (ECDL) capacitors. Two distinct synthesis methods, hydrothermal route and co-precipitation method, were employed to fabricate C@CdS materials, each resulting in unique morphology and growth mechanisms. Detailed microstructural analyses, including high-resolution transmission electron microscopy (HR-TEM) and X-ray diffraction (XRD), revealed nanosheets in co-precipitated sample (CCSP) and core-shell structures in hydrothermally synthesized sample (CCSA). Optical investigations using UV-Vis spectroscopy provided insights into the absorbance properties of the synthesized materials. Electrical characterization, including frequency response testing and impedance analysis, demonstrated distinct capacitive behaviours for CCSP and CCSA, highlighting their potential for use in energy storage applications. Electrical characterization, including frequency response testing, impedance analysis, and galvanostatic charge-discharge (GCD) curve analysis, demonstrated distinct capacitive behaviours for CCSP and CCSA, highlighting their potential for use in energy storage applications. The integration of optical, structural, and electrical analyses provides a comprehensive understanding of the synthesized C@CdS core-shell nanostructures, offering insights into their potential application for ECDL capacitor technology and other emerging energy storage applications. Further optimization of synthesis parameters and exploration of scalable production methods are suggested for future research endeavors.

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.

Granulated graphene oxide-activated carbon for adsorptive removal of diclofenac sodium and ibuprofen in a continuous fixed-bed column

The granular graphene oxide-activated carbon (GGA) composite was synthesized with polyvinyl alcohol (PVA) and malonic acid (MA) as chemical crosslinker at different conditions. GGA synthesis was performed at different parameters including binder-to-powder ratio in the range of 0.5–1.2, synthesis time in the range of 2-24 h, and drying temperature in the range of 60-110 °C. Response surface methodology (RSM) was used to optimize the synthesis parameters of the adsorbent synthesis. The optimum parameters for synthesis were achieved at a binder-to-powder ratio of 0.875, a synthesis time of 23.992 h, and a drying temperature of 60.071 °C. XRD, FTIR, FE-SEM, BET and TGA analyses were used to discuss the characteristics of the adsorbent structures. The surface area and mechanical stability were found to be 156.59 m2/g and 95.417%, respectively. The adsorption behavior of mono-components (diclofenac sodium (DCF)/ibuprofen (IBP)) and bi-components (DCF+IBP) on the GGA was evaluated in a fixed-bed column. The effects of column operating parameters, including bed mass (m: 0.25-0.75 g), flow rate (Q: 5-9 mL/min), and adsorbate concentration for DCF (C: 20-100 mg/L) and IBP (C: 5-15 mg/L) on the breakthrough curves were investigated. The experimental data of fixed-bed column were correlated with breakthrough models such as Thomas, Bohart-Adams, Yoon-Nelson, Yan, Gompertz, and Log-Gompertz via both linear (under different column operating conditions) and nonlinear (for DCF (Co of 60 mg/L; m of 0.5 g and Q of 7 mL/min) and IBP (Co of 10 mg/L; m of 0.5 g and Q of 7 mL/min)) regression analysis. The maximum adsorption capacities calculated by the Thomas model were 110.068 and 34.912 mg/g for DCF and IBP, respectively. In bi-component systems, antagonistic behavior was observed in the adsorption of DCF and IBP. The results showed that the GGA can successfully remove DCF and IBP through a fixed-bed adsorption column.

Structural, Morphological, Optical, and Magnetic Properties of NiO-added NiCo2O4 Electrode Materials Synthesized by Sol-Gel, Co-Precipitation and Ultrasonication Methods and their Electrochemical Supercapacitor Response

In this study, NiO-added NiCo2O4 composite samples were prepared using three distinct synthesis methods to study the impact of synthesis technique and NiO addition on the electrochemical performance of NiCo2O4. The chosen methods, sol-gel, co-precipitation, and ultrasonication, represent a range of approaches that yield different particle structures and morphologies. The structural and morphological studies of composite samples were investigated using X-ray diffraction (XRD) and field emission scanning electron microscope (FESEM), respectively. XRD analysis revealed the crystalline composition, revealing the presence of two distinct phases: NiO and NiCo2O4. The Rietveld analysis of the composite samples supports the dual phases in the samples. FESEM analysis confirms the change in size and shape of the particles with the synthesis procedure. Optical properties, measured via UV-visible absorbance spectra, demonstrated that the energy gap varied with the synthesis method. The sol-gel samples exhibited the highest energy gap at 2.20 eV. The magnetic properties were measured using the vibration sample magnetometer (VSM), and the results confirm that the synthesis procedure influences magnetic loops and coercivity. The electrochemical performance of the samples in a 3 M potassium hydroxide electrolyte revealed that the co-precipitation method produced the highest capacitance of 398 Fg-1 at a 10 mV/s sweep rate, indicating superior energy storage capacity compared to pure NiCo2O4. Adding NiO phase to the NiCo2O4 matrix is believed to enhance electrochemical performance by creating additional charge at the grain boundaries, leading to a synergistic effect and improved electron and ion transport. The exceptional electrochemical performance of these composite materials suggests that the synthesis methods and the addition of NiO play a critical role in determining the overall efficiency and applicability of battery-type supercapacitors. These findings pave the way for further research into optimizing synthesis parameters to enhance energy storage capacity and inspire the development of advanced spinel metal oxide composite electrodes for supercapacitors and other energy storage applications.

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).

Structure optimization of ceramic-based metal−organic framework membrane for efficient desalination

To address global water pollution and crisis issue, wastewater recycling, seawater and brackish water desalination have been increasingly utilized to produce clean water. Ceramic membranes have been gaining widespread interest due to their unique physicochemical properties and high stability. Integrating nanoporous MOF (metal organic framework) with ceramic membranes could enable a rational design of ceramic-based MOF membranes with enhance sieving performance. Herein, we report an in-situ method to construct an inter-crystalline defect-free MOF layer on ZrO2 ceramic membranes for efficient desalination application. After optimizing synthesis parameters, an inter-crystalline defect-free and well-intergrown ceramic-based MOF membrane was obtained. The ceramic-based MOF membranes not only demonstrated a near-complete salt rejection, but also exhibited high water flux, which are superior to most of the reported zeolite and MOF membranes. In addition, the MOF membranes exhibited promising performance and structure stability even when exposed to harsh water environments. Our work introduces a protocol for the design of high-performance ceramic-based MOF membrane as a promising candidate for challenging desalination applications under different environments.

A review of synthesis strategies for nickel cobaltite-based composites in supercapacitor applications

Supercapacitors (SCs), known for their exceptional power and reasonably high energy densities, long lifespan, and lower production costs, have emerged as an ideal solution to meet the growing demand for various energy storage applications. The characteristics of supercapacitors are greatly influenced utilizing the choice of electrode materials, developing novel electrode materials a focal point for extensive research in the field of high-performance supercapacitors. In recent years, NiCo2O4 has garnered increasing attention as a supercapacitor electrode material owing to its notable edges, including high theoretical capacity, low cost, abundant availability, and ease of synthesizing. However, the performance of NiCo2O4 is hindered by its low electrical conductivity and limited surface area, leading to significant capacity deterioration. Therefore, it is imperative to systematically and comprehensively summarize the advancements in comprehending and adjusting NiCo2O4-based electrodes from multiple perspectives. The present review primarily focuses on the synthetic approaches employed to produce NiCo2O4 nanomaterials with diverse morphologies for their application in supercapacitors. This review article provides a comprehensive overview of the synthesis approaches utilized for developing nickel cobaltite-based composites tailored for supercapacitor applications. Various synthesis methods, including sol-gel, hydrothermal, and co-precipitation techniques, are discussed in detail, emphasizing the importance of optimizing synthesis parameters to enhance the electrochemical performance of the composites. The potential applications of nickel cobaltite-based composites in supercapacitors are explored, highlighting their promising prospects in energy storage technologies. Future research directions in this field are also discussed.

Active Learning-Based Guided Synthesis of Engineered Biochar for CO2 Capture.

Biomass waste-derived engineered biochar for CO2 capture presents a viable route for climate change mitigation and sustainable waste management. However, optimally synthesizing them for enhanced performance is time- and labor-intensive. To address these issues, we devise an active learning strategy to guide and expedite their synthesis with improved CO2 adsorption capacities. Our framework learns from experimental data and recommends optimal synthesis parameters, aiming to maximize the narrow micropore volume of engineered biochar, which exhibits a linear correlation with its CO2 adsorption capacity. We experimentally validate the active learning predictions, and these data are iteratively leveraged for subsequent model training and revalidation, thereby establishing a closed loop. Over three active learning cycles, we synthesized 16 property-specific engineered biochar samples such that the CO2 uptake nearly doubled by the final round. We demonstrate a data-driven workflow to accelerate the development of high-performance engineered biochar with enhanced CO2 uptake and broader applications as a functional material.

Graphene oxide as an emerging sole adsorbent and photocatalyst: Chemistry of synthesis and tailoring properties for removal of emerging contaminants

Contaminants of emerging concern (CEC) contain a wide range of compounds, such as pharmaceutical waste, pesticides, herbicides, industrial chemicals, organic dyes, etc. Their presence in the surrounding has extensive and multifaceted effects on human health as they have the potential to persist in the environment, accumulate in biota, and disrupt ecosystems. In this regard, various remediation methods involving different kind of functional nanomaterials with unique properties have been developed. The functional nanomaterials can provide several mechanisms for water pollutant removal, such as adsorption, catalysis, and disinfection, in a single platform. Graphene oxide (GO) is a two-dimensional carbon-based material that has an extremely large surface area and a large number of active sites. Recent advances in synthesising GO have shown great progress in tailoring its various physiochemical, optical, surface, structural properties etc., making it better adsorbent and photocatalysts. In this review, sole adsorbent and standalone photocatalytic performances of GO for the removal of CEC have been discussed in light of tailoring its adsorption and photocatalytic properties through novel synthesis routes and optimizing synthesis parameters. This review also examines various models describing the structure of GO and its surface/structural modifications for improved adsorption and photocatalytic properties. The article provides valuable information for the production of efficient and cost-effective GO-based sole adsorbents and photocatalysts as compared to the traditional materials. Furthermore, future prospective and challenges for sole GO nanostructures to compete with traditional adsorbents and photocatalysts have been discussed providing interesting avenues for future research.

Photoluminescence enhancement of chemical vapor-deposited MoSe2 monolayers

The transition metal dichalcogenide (TMDC) materials have attracted a great interest owing to their superior features. The chemical vapor deposition (CVD) is very feasible to synthesis of TMDC materials. The thermal expansion coefficient difference between TMDC materials and substrate in the CVD synthesis can cause a strain, resulting in non-radiative recombination and PL decrement for these materials. Therefore, in this work, we studied acetone and isopropanol (IPA) treatment on the photoluminescence (PL) properties of CVD-grown MoSe2 monolayers. Firstly, monolayer MoSe2 flakes on SiO2/Si substrates were synthesized via the CVD method by optimizing synthesis parameters. The Raman and PL measurements were taken after acetone and IPA treatments were applied to grown samples. The results indicated an important PL enhancement was seen for acetone treatment. For IPA treatment, there was a PL peak position shifting with decreasing intensity due to its possible structural damage. The acetone, IPA, and transfer processes caused the releasing strain on MoSe2 by breaking the strong interaction between MoSe2 and substrate. For the whole treatment, PL peaks shift to blue with about 80 meV. As a result of the present study, acetone treatment was found as an easy and quick way to enhance radiative emission of CVD-grown MoSe2.

XRD analysis of Spirulina platensis mediated TiO2NPs

This study explores the synthesis of titanium dioxide nanoparticles (TiO2NPs) mediated by Spirulina platensis (S. platensis) and presents the corresponding X-ray diffraction (XRD) results. The analysis of the XRD patterns confirms the successful formation of crystalline nanoparticles, with distinct peaks aligning with the anatase phase of titanium dioxide. The utilization of S. platensis as a mediator not only facilitates the generation of TiO2NPs but also introduces a bio-friendly and sustainable dimension to the synthesis process. The anatase phase is known for its advantageous properties, including photocatalytic activity and stability, suggesting the potential of the synthesized nanoparticles for applications such as environmental remediation, catalysis, and photovoltaic devices. This study contributes valuable insights into the S. platensis-mediated synthesis of TiO2NPs, emphasizing their promising prospects for diverse technological applications. Further research can delve into optimizing synthesis parameters to enhance nanoparticle properties, promoting their effective utilization in various fields.

Statistical Design-Guided Synthesis of Nanoarchitectonics of High-Performance NiFeMoN Electrocatalyst through Facile One-Step Magnetron Sputtering.

This study presents an innovative, statistically-guided magnetron sputtering technique for creating nanoarchitectonics of high-performing, NiFeMoN electrocatalysts for oxygen evolution reaction (OER) in water splitting. Using a central composite face-centered (CCF) design, 13 experimental conditions are identified that enable precise optimization of synthesis parameters through response surface methodology (RSM), confirmed by analysis of variance (ANOVA). The statistical analysis highlighted a interaction between Mo% and N% in the nanostructured NiFeMoN and found optimizing values at 31.35% Mo and 47.12% N. The NiFeMoN catalyst demonstrated superior performance with a low overpotential of 216mV at 10mA cm-2 and remarkable stability over seven days, attributed to the modifications in electronic structure and the creation of new active sites through Mo and N additions. Furthermore, the NiFeMoN coating, when used as a protective layer for a Si photoanode in 1m KOH, achieved an applied-bias photon-to-current efficiency (ABPE) of 5.2%, maintaining stability for 76 h. These advancements underscore the profound potential of employing statistical design for optimizing synthesis parameters of intricate catalyst materials via magnetron sputtering, paving the way for accelerated advancements in water splitting technologies and also in other energy conversion systems, such as nitrogen reduction and CO2 conversion.

Top‐down Surfactant‐Free Synthesis of Supported Palladium‐Nanostructured Catalysts

Nanostructured palladium (Pd) is a universal catalyst that is widely used in applications ranging from catalytic converters of combustion engine cars to hydrogenation catalysts in industrial processes. Standard protocols for synthesizing such nanoparticles (NPs) typically use bottom‐up approaches. They utilize special and often expensive physical techniques or wet‐chemical methods requiring organic surfactants. These surfactants should often be removed before catalytic applications. In this article, the synthesis of Pd NPs immobilized on carbon support by electrochemical erosion without using any surfactants or toxic materials is reported. The Pd NPs synthesis essentially relies on a Pd bulk pretreatment, which causes material embrittlement and allows the erosion process to evolve more efficiently, producing homogeneously distributed NPs on the support. Moreover, the synthesized catalyst is tested for hydrogen evolution reaction. The activity evaluations identify optimal synthesis parameters related to the erosion procedure. The electrocatalytic properties of the Pd NPs produced with sizes down to 6.4 ± 2.9 nm are compared with a commercially available Pd/C catalyst. The synthesized catalyst outperforms the commercial catalyst within all properties, like specific surface area, geometric activity, mass activity, specific activity, and durability.

Mn-promoted MoS2 catalysts for CO2 hydrogenation: enhanced methanol selectivity due to MoS2/MnOx interfaces.

Considering the alarming scenario of climate change, CO2 hydrogenation to methanol is considered a key process for phasing out fossil fuels by means of CO2 utilization. In this context, MoS2 catalysts have recently shown to be promising catalysts for this reaction, especially in the presence of abundant basal-plane sulfur vacancies and due to synergistic mechanisms with other phases. In this work, Mn-promoted MoS2 prepared by a hydrothermal method presents considerable selectivity for CO2 hydrogenation to methanol in comparison with pure MoS2 and other promoters such as K and Co. Interestingly, if CO is used as a carbon source for the reaction, methanol production is remarkably lower, which suggests the absence of a CO intermediate during CO2 hydrogenation to methanol. After optimization of synthesis parameters, a methanol selectivity of 64% is achieved at a CO2 conversion of 2.8% under 180 °C. According to material characterization by X-ray Diffraction and X-ray Absorption, the Mn promoter is present mainly in the form of MnO and MnCO3 phases, with the latter undergoing convertion to MnO upon H2 pretreatment. However, following exposure to reaction conditions, X-ray photoelectron spectroscopy suggests that higher oxidation states of Mn may be present at the surface, suggesting that the improved catalytic activity for CO2 hydrogenation to methanol arises from a synergy between MoS2 and MnOx at the catalyst surface.

Comprehensive study of the synthetic tychite, Na6Mg2(CO3)4SO4: synthesis, structure and conductive properties.

The structural and conductive properties of the synthetic tychite Na6Mg2(CO3)4SO4 (space group: Fd3̄) were explored. Optimal synthesis parameters were selected by varying the molar ratio of reagents, synthesis temperature and time. For structural descriptions, we carried out scanning electron microscopy, thermal analysis, and Raman and Fourier-transform infrared spectroscopy. We carried out theoretical and experimental studies of conductivity. Theoretical calculations were obtained using geometrical-topological analysis based on Voronoi partitioning (the evaluation of geometrical sizes of voids and channels), the bond valence site energy (BVSE) method (the fast calculation of migration energies, Em), kinetic Monte Carlo simulation (the estimation of ionic conductivity at different temperatures), and density functional theory (the precise assessment of Em and vacancy formation energies). The experimental techniques included electrochemical impedance spectroscopy EIS (total conductivity determination) and direct current DC polarization (electronic conductivity assessment) measurements. Na6Mg2(CO3)4SO4 was found to have a three-periodic Na+-ion migration map with an Em of 0.37 eV and 0.18 eV from BVSE and DFT results, respectively. The theoretical value of cationic conductivity was 2.6 × 10-7 S cm-1 at 100 °C. The experimental total conductivity was equal to 6.0 × 10-7 S cm-1 at 100 °C, which is close to theoretical results. Using additional DC polarization, the electronic contribution to the total conductivity was characterized as insignificant.

Synthesis of calcium propionate from indigenous limestone from Swat area in Pakistan

In this study, native limestone from the Swat area of Pakistan was used for the synthesis of calcium propionate. The powdered limestone was allowed to react with propionic acid and the effect of the synthesis parameters, that is, the particle size (50, 100, 150, and 200 mesh), propionic acid (10, 15, and 30 %), solid-liquid ratio (0.1:10, 0.12:1, 0.14:1, and 0.16:1), reaction time (1, 1.5, 2, and 2.5 hours) and the temperature (60, 80, 90, and 100 °C) on the percentage yield and purity of calcium propionate was studied. The results showed that the optimum synthesis parameters were 200 mesh particle size, 15% propionic acid concentration, 0.14:1 solid-liquid ratio, 2.5 hours reaction time, and 80 °C temperature. The product obtained under optimal conditions was characterized by infrared spectroscopy, thermogravimetry, and scanning electron microscopy. The results revealed that a product having ≥ 99.8% purity with 85% yield can be obtained by this process.

INVESTIGATION OF THE INFLUENCE OF SILICON NANOWIRE SYNTHESIS PARAMETERS ON THE CHARACTERISTICS OF PHOTOSENSITIVE SENSORS

Problem. Photosensitive sensors are widely used both in everyday life in climate systems and in communication devices and street lighting. In order to improve the performance parameters of photosensitive sensors, the use of silicon nanowires (SiNWs) has been proposed. A large number of articles are dedicated to the influence of synthesis parameters on the dimensions of SiNWs. However, there is a lack of research on the impact of the surface morphology of SiNW arrays on the electrical and photosensitive parameters of sensors based on them.The purpose of the work The aim of this work is to synthesize silicon nanowires using the metal-assisted chemical etching method, investigate their surface morphology, and fabricate photodiodes based on them to examine the influence of SiNW synthesis parameters on the characteristics of photosensitive sensors, considering the peculiarities of their structure.Research results. Photosensitive sensors of diode type based on SiNWs were synthesized and investigated. The influence of the following synthesis parameters of SiNWs on their lateral and vertical morphology as well as on characteristics of diode sensors based on them was demonstrated: the duration of the first and second stages of metal-assisted chemical etching (MACE), the content of silver nitride and hydrogen peroxide in the solutions of the first and second stages of MACE, as well as surface texturing and processing in isotropic and anisotropic etchants. The maximum operational parameters of the obtained photosensitivity sensors based on the SiNW array were as follows: rectification coefficient of 1320 and photosensitivity coefficient of 3.1 mA/lmV.Conclusions. The obtained results indicate that the technological parameters of the first and second stages of MACE, as well as pre- and post- chemical treatments, have a significant influence on increasing of the surface roughness, height, and porosity of SiNWs, which in turn affect the electric and photosensitive parameters of the sensors. Optimal SiNWs synthesis parameters for achieving of maximum photosensitivity have been established.

Синтез кобальтата лития стехиометрического состава комбинированным золь-гель методом с твердофазным окончанием без использования длительной высокотемпературной обработки

Lithium cobaltate (LiCoO2) of stoichiometric composition was synthesized by an improved sol-gel method combined with a solid-state method. Originality of this paper is that, cobalt oxidation is used not by long-term high temperature treatment, but by bubbling with air oxygen (Co2+→Co3+) during sol-gel synthesis. A fundamental schematic diagram of the synthesis has been developed based on experimental results. The electrophysical properties of lithium cobaltate were determined (electronic ionic conductivity) and physical properties (particle size, specific surface area). The optimal synthesis parameters were established.

Interlayer spacing-controlled carnation flower-like microstructure of nickel-manganese layered double hydroxide for enhancing hybrid supercapacitor performance

Energy harvested from intermittent sources can be stored in supercapacitors for high-power delivery with long cycling stability. Binary layered double hydroxide (LDH) materials have great potential for hybrid supercapacitor applications owing to their mixed and tunable charges and layered structure. This study presents carnation flower-like, 3D micro-structured NiMn-LDH prepared by a facile single-step hydrothermal synthesis using hexamethylenetetramine to produce hydroxides. The 3D structure was assembled from ultrathin 2D NiMn-LDH nanosheets, and the largest interlayer spacing was obtained by optimizing synthesis parameters, such as Ni:Mn molar ratio and reaction temperature, ensuring a fast diffusion and thus the best energy storage performance. The optimized NiMn-LDH electrode delivered a high specific capacity of 612 C g−1 with an excellent rate capability of 67% at 20 A g−1 in a three-electrode test. An asymmetric device assembled using NiMn-LDH and reduced graphene oxide as positive and negative electrodes provided a high energy density of 60.0 Wh kg−1 and power density of 17.7 kW kg−1 with 90.4% capacity retention after 10,000 charge–discharge cycles. This superior result highlights the potential industrial applications, such as portable electronics and trams.

Synthesis of Mo2C-based material in DC arc discharge plasma under ambient air conditions

Molybdenum carbide is a well-known material, which properties makes it good candidate for replacing platinum in hydrogen production by electrolysis. Mo2C phase shows the best characteristics among other molybdenum carbide phases in HER. In this paper Mo2C-based powder material has been synthesized by non-vacuum DC arc discharge method. The main advantage of the method is the synthesis under ambient air conditions, which leads to low cost and more effectiveness of the process. We carried out several series of experiments to determine the optimal synthesis parameters that ensure the dominance of the Mo2C phase in the synthesis product. Carbon nanofibers (CNFs) obtained via catalytic pyrolysis of ethylene on Ni–Cu alloy were used as a carbon source. CNFs were characterized by SEM and low-temperature adsorption/desorption of N2. According to XRD analysis, the optimal ratio of the initial components C:Mo is 1:16 wt, arc current is 200 A, and plasma exposure time is 30 s. In this paper, for the first time the oxidation behavior of the Mo2C-based material, obtained in DC arc discharge plasma under ambient air conditions, was investigated by TG/DTA. The noble metal free HER electrocatalyst with the synthesized material as precursor was prepared for investigation of electrocatalytic activity.