Papers by Keyword: Hydrothermal

Abstract: A hybrid supercapacitor is an energy storage device that combines the properties of EDLCs and pseudocapacitors. In this research, the goal was to analyze the effect of hydrothermal temperature on the structure, morphology, and capacitive properties of the N-Doped reduced graphene oxide/Copper Chromite (N-Doped rGO/CuCr₂O₄) composite, which was being investigated as a potential material for hybrid supercapacitor electrodes. The method used was hydrothermal, with temperature variations of 120°C, 140°C, and 160°C. The structure and morphology of the composites were analyzed using Scanning Electron Microscope (SEM) and Energy Dispersive X-Ray Analysis (EDX), X-Ray Diffractometer (XRD), and Fourier Transform Infrared Spectrometer (FTIR). Meanwhile, the capacitance and conductivity values of N-doped rGO/CuCr₂O₄ were measured using Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS) tests. The results of the XRD tests showed that an increase in temperature led to a greater d_spacing value, indicating the presence of more substituted nitrogen atoms. This was supported by the results from EDX, which showed that the sample with a hydrothermal temperature of 160°C had the largest percentage of nitrogen. Nitrogen is important in increasing the conductivity of the material. The FTIR results revealed a covalent bond between Carbon (C) and Nitrogen (N). Meanwhile, the results of the CV test, performed at a scan rate of 5 mV/s and a potential window of 0-0.8 V, showed that the specific capacitance values were 99.5, 196.16, and 221.59 Fg^-1 for the samples with hydrothermal temperatures of 120°C, 140°C, and 160°C, respectively. The EIS test measured the conductivity values of the samples, which were 0.123, 0.518, and 0.549 S/m for the samples with hydrothermal temperatures of 120°C, 140°C, and 160°C, respectively. Thus, the specific capacitance values were influenced by the electrical conductivity of the materials and the nitrogen doping content in the electrode composite material.

Abstract: Titanate nanosheets are a type of 2-dimensional nanomaterial with vast applications in electronics, energy storage, and photocatalysis due to their superior properties, such as their large specific surface area and excellent electrical conductivity. Titanate nanosheets are expected to be the material precursor of TiO₂ nanostructures with further treatment. The current research aims to synthesize titanate nanosheets using the natural mineral ilmenite from Indonesia through the hydrothermal method. X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM), and Brunaeur-Emmett-Teller (BET) analysis were used to characterize the chemical composition, crystal structure, shape, size, and specific surface area of the prepared samples. The structure phase of the as-synthesized sample is known to be layered titanate. The as-synthesized nanosheet sample has a diameter ranging from 2.5 to 4 μm and BET surface areas of approximately 40 m²/g. This concise hydrothermal method could create 2-dimensional structured nanomaterials from Indonesian local minerals.

Abstract: Using a facile hydrothermal method, ZnO nanomaterials with various morphological structures (nanowires, nanodiscs, and nanostars) were produced. An investigation was conducted into the relationships between the exposed polar facets and the photocatalytic activities. Based on XPS, Pl, and structural analysis, it was discovered that the exposed facets’ chemsorption ability of the different ZnO nanomaterials with different morphologies plays a vital role in their photocatalytic properties. Zinc-terminated surfaces had the highest chemsorption ability and consequently the ZnO nanodiscs with the highest fraction of exposed Zinc-terminated facets were the ideal photocatalysts from the tested morphologies. This work emphasises the important influence of rational control over the nanomaterial morphology on its physical and chemical properties and therefore on its performance in various practical applications.

Abstract: Industrial dyes contained a wide range of organic compounds that could affect the environment and high dimensional challenges to humans. In recent years, the environmentally safe and inexpensive quaternary copper-based chalcogenide Cu₂ZnSnS₄ (CZTS) has emerged as a material for photovoltaics and photocatalysis. CZTS nanoparticles were prepared in this investigation using the hydrothermal route at 210 °C for 24 h without the addition of a surfactant or capping agents. Rhodamine B (RhB), a carcinogenic dye, was degraded using the synthesized material through a photocatalytic process. The structural, morphological, optical, and photocatalytic characteristics of CZTS nanoparticles were examined using X-ray diffraction (XRD), Raman spectroscopy, Field emission scanning electron microscopy (FE-SEM), and UV-vis spectroscopy. The average particle size of CZTS is found to be 31 nm with crystalline nature have been characterized by XRD. The results demonstrate that the synthesized sample has mixed morphological structures such as clew-like and flower-like structures and a bandgap of 1.50 eV. CZTS nanoparticles were used as photocatalysts under direct sunlight for Rhodamine B degradation, with the fastest degradation efficiency of 72% at 50 minutes. The results show that surfactant-free hydrothermally synthesized CZTS nanoparticles are a very promising material for the degradation of RhB dye due to the rapid degradation rate and high degradation efficiency.

Abstract: An electrical insulator known as a dielectric material is a substance that can be solid, liquid, or gaseous. Having a high specific resistance, a dielectric material is a non-metallic substance. A dielectric function as the perfect capacitor, storing and dissipating electrical energy. Due to the rising need for capacitors, semiconductor devices, Liquid Crystal Displays, electrical transformers, and other products, properties including electric susceptibility, dielectric polarisation, dispersion, relaxation, and tunability have received a great deal of attention. Advanced materials must be developed in order to further enhance their performance. Metal-organic frameworks (MOFs), a class of porous crystalline solids, have shown to be ideal models for synthesising functional materials that may be used to make supercapacitor electrodes. Greater electrical conductivity, a higher charge capacity, and variable electrochemical activity are just a few benefits that bimetallic MOFs and their derivatives have over monometallic MOFs. This study focuses on the usage of MOF-derived bimetallic in dielectric materials, with particular attention paid to understanding the cause of the enhanced performance and covering the most recent advancements in the area with a variety of applications.

Abstract: In this research, a homemade autoclave reactor was used for preparing iron oxide nanoparticles by hydrothermal technique at different reaction times by using ferric chloride, ferrous sulfate, and ammonium hydroxide as raw materials. The XRD characterization showed that the nanoparticles of the samples have high crystallinity with the crystal phase of magnetite, furthermore, the crystal phase of hematite appears clearly as the reaction time increased. The SEM results showed when the time of reaction increased the average particle size increased too from 28.1 to 49.2 nm. That means the reaction time is an effective parameter for the nanoparticle's growth, The EDX spectrum verified the confirmation of iron oxide nanoparticles by the appearance of Iron and Oxygen peaks. The FT-IR results showed that all samples have an absorption peak at about 578 cm^-1 corresponding to the Fe-O bond stretching modes of the in magnetite and the peak of hematite appeared as the reaction time increased above 2 hours which was confirmed with XRD results. Finally, the reaction time is a powerful tool for controlling in size and phase of nanoparticle preparation. Keywords: Hydrothermal, Iron Oxide, Reaction time, magnetite, and hematite.

Abstract: Increasing the demand to explore the nanomaterials properties to be used in numerous applications have emerged considerable effort to developing synthesis methods. Herein, Tin oxide (SnO₂) nanosheets have been prepared by a facile one step hydrothermal method using Teflon-lined steel at synthesis temperature of 120 C for 12 hours. As synthesis material were characterized by Field emission scanning electron microscopy (FESEM) and x-ray diffraction (XRD) to revealing the morphology and structural properties. As a result, SnO₂ nanosheets have been obtained with thickness around 15 nm with a clear sheets morphology. XRD pattern showed one phase structural with absence of impurities phases. Optical properties for nanosheets suspended in ethanol were investigated using steady state photoluminescence and UV-Vis absorption technics. The result showed four peaks centered at 380 nm, 445 nm, 475 nm, and 500 nm related to near band to band emission and defects states. Keywords: SnO2, Nanosheets, hydrothermal, XRD

Abstract: CoO nanocrystal is well-known photocatalyst for overall water splitting. However it suffers from a very short lifetime of only 1 h. The poor stability is derived from carrier recombination-induced thermal oxidation. This research will provide information about synthesis of CoO/ZnO nanocrystalline that can potentially enhance photocatalysts. CoO has been synthesized first under hydrothermal method, followed by calcination process. Thereafter, CoO has been used to produce CoO/ZnO under precipitation method. The samples were characterized using XRD (X-Ray Diffraction), FTIR (Fourier Transform Infrared Spectroscopy), and UV-VIS (UV–Visible Spectroscopy) to analyze their composition, chemical functional group, optical absorption, and band gap. The XRD spectrum showed that CoO/ZnO had cubic spinel and hexagonal phase structure with crystallite size of 69.0, 46.4, 32.8, and 32,4 nm. The bands in obtained FTIR spectrum at 586.36, 671.23, and 410-429 cm⁻¹ were correlated with vibrations of the Co³⁺ in octahedral hole, the Co²⁺ in tetrahedral hole, and Zn-O, respectively. The band gap energy of CoO, CoO/ZnO with variation of 1:1 and 1:3 were 4.39, 4.14, and 3.65 eV, respectively. The photocatalytic activities of CoO/ZnO were confirmed by methylene blue dyes photodegradation of 663 nm under UV light irradiation in aqueous solution. The 22.4% methylene blue can be removed within 3 h. Overall, these findings reveal the potential of CoO/ZnO for practical application.

Abstract: In this study, a novel reduced graphene oxide, indium (III) oxide, and molybdenum disulfide (rGO/In₂O₃/MoS₂) ternary composite for supercapacitor electrode application was developed via green hydrothermal synthesis. The topography, surface morphology, crystalline structure, phase identification and molecular structure of the composites were examined by applying Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDX), Transmission Electron Microscopy (TEM), X-ray Diffraction Spectroscopy (XRD), X-Ray Photoelectron Spectroscopy (XPS), and Raman Spectroscopy. SEM and TEM reveal the uniform dispersion of In₂O₃ nanoparticles on the rGO and MoS₂ sheets. EDX, XRD, and XPS analysis confirm the coexistences of rGO, In₂O₃, and MoS₂, and hence the composite formation. The electrochemical performances of rGO/In₂O₃/MoS₂ ternary composite were evaluated by cyclic voltammetry (CV) in two-electrode configuration in 1 M sodium sulfite (Na₂SO₃) aqueous electrolyte. The electrochemical results show that the rGO/In₂O₃/MoS₂ composite electrodes possess improved specific capacitance of 77 F/g at a scan rate of 25 mV/s, a modest 29% enhancement over pure In₂O₃ and In₂O₃/MoS₂ binary composite.

Abstract: This research paper describes the effect of hydrogen peroxide concentrations (0; 1; 3; 5 and 7 wt%) on fluorescence properties of carbon dots (CDs) from high-density polyethylene (HDPE) plastic. Synthesis of CDs has been carried out using modified pyrolysis and hydrothermal methods. The CDs obtained were characterized by FTIR, XRD, UV-Visible and fluorescence spectrophotometer. Based on UV-Visible spectra, the maximum wavelength of carbon dot ranges from 287 to 291 nm, indicating there is an π -π* electron transition belonging to the core site (C=C), then the absorption widens to 400 nm which indicated n-π* electron transition relating to the CDs surface functional group (carbonyl, hydroxyl, and carboxyl). The use of hydrogen peroxide (5 wt%) can produce CDs with the best fluorescence properties based on fluorescence spectra. CDs has a structure like graphite which is rich in functional groups on its surface. The photocatalytic activity of carbon dot has been tested and it showed that CDs can degrade methylene blue (MB) dye under visible light (80.3%).