Kimya Mühendisliği Bölümü Makale Koleksiyonu

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https://hdl.handle.net/20.500.12418/625

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Calcium phosphate nano powder biosynthesis from sea urchin shells: a response surface approach
(2024) Öksüz, K. Emre
In this experimental study, calcium phos phate Ca3(PO4)2 nanopowders, in the form of nano hydroxyapatite (n-HA), were successfully synthesized from sea urchin shells (Diadema setosum, Leske, 1778) via a process involving precipitation and heat treatment method at various calcination tempera tures (800 to 1200 °C). The optimal conditions for producing n-HA with maximum free CaO content were determined using response surface methodology (RSM) through a Box–Behnken Design. Key findings demonstrated that calcination temperature, calcina tion time, and ball-milling time significantly influ enced the free CaO content. The study identified that Highlights • (Ca3(PO4)2) NPs namely hydroxyapatite were synthesized by the wet chemical precipitation process using sea urchin (D. setosum) through the response surface method (RSM). • Calcination temperature was determined by RSM to be a key factor in controlling the % CaO. • Spectral analyses and phase identification were investigated in detail for the (Ca3(PO4)2) NPs. • Homogenous dispersions of (Ca3(PO4)2) NPs exhibited constant zeta potential. K. E. Öksüz (*) Department of Metallurgical and Materials Engineering, Faculty of Engineering, Sivas Cumhuriyet University, 58140 Sivas, Türkiye e-mail: emre.oksuz@cumhuriyet.edu.tr K. E. Öksüz · İ. Şen · M. Erşan Department of Bioengineering, Institute of Science and Technology, Sivas Cumhuriyet University, Sivas 58140, Türkiye a calcination temperature of 1100.73 °C for 2.78 h for CaO derived from sea urchin shells, combined with a ball-milling time of 66.37 h, resulted in the highest purity of n-HA. The biosynthesized n-HA exhibited desirable characteristics for bone and dental restora tion applications, as confirmed by comprehensive analyses of functional group vibrations, chemical structure/composition, molecular interactions, sur face morphology, and particle size distribution. These f indings underscore the potential of using invasive sea urchin shells as a sustainable and effective source for n-HA production in biomedical applications
Calcium phosphate nano powder biosynthesis from sea urchin shells: a response surface approach
(2024) Öksüz, K. Emre; Şen, İlker; Erşan, Mehtap
In this experimental study, calcium phos phate Ca3(PO4)2 nanopowders, in the form of nano hydroxyapatite (n-HA), were successfully synthesized from sea urchin shells (Diadema setosum, Leske, 1778) via a process involving precipitation and heat treatment method at various calcination tempera tures (800 to 1200 °C). The optimal conditions for producing n-HA with maximum free CaO content were determined using response surface methodology (RSM) through a Box–Behnken Design. Key findings demonstrated that calcination temperature, calcina tion time, and ball-milling time significantly influ enced the free CaO content. The study identified that a calcination temperature of 1100.73 °C for 2.78 h for CaO derived from sea urchin shells, combined with a ball-milling time of 66.37 h, resulted in the highest purity of n-HA. The biosynthesized n-HA exhibited desirable characteristics for bone and dental restora tion applications, as confirmed by comprehensive analyses of functional group vibrations, chemical structure/composition, molecular interactions, sur face morphology, and particle size distribution. These f indings underscore the potential of using invasive sea urchin shells as a sustainable and effective source for n-HA production in biomedical applications.
Optimization of reduced graphene oxide yield using response surface methodology
(2024) Anaklı, Duygu; Erşan, Mehtap
The efficient synthesis of reduced graphene oxide (RGO) by one-step chemical reduction of graphene oxide (GO) was carried out using sodium sulfate (Na 2 SO 4 ) as a reducing agent. The aim of this study was to find the optimum conditions for the production of RGO as a function of reduction time, reduction temperature and GO:Na 2 SO 4 weight ratio. The Box-Behnken design (BBD) method of the Response surface methodology (RSM) was used to optimize three variable factors (reduction temperature (25–95 C), reduction time (1 12h), GO:Na weightratio ([1:1]-[1:20]) on the RGO yield. The optimum conditions obtained by the RSM method were given as a weight ratio of [1:10.5] GO:Na 2 SO ◦ 2 SO SO 4 , a reduction temperature of 60 4 C, and a reduction time of 6.5 h. The predicted optimum conditions obtained by RSM showed that the amount of RGO increased with the weight ratio of the GO:Na 2 4 . The obtained RGO was characterized by using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Raman spectroscopy, Brunauer-Emmett-Teller (BET), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and ultraviolet-visible (UV–Vis) spectroscopy to confirm that high quality RGO was synthesized with appropriate amount. XRD analysis suggested that the π-conjugated structure of RGO was significantly restored with the removal of oxygen functional groups. The RSM method can improve the experiment as a low cost method thatcan be used with a small number of experiments and experimental materials to give the highest yield of RGO.
Removal of Reactive Red120 from Aqueous Solutions by Graphene Oxide/Zirconium Oxide Nanocomposites
(2024) Anaklı, Duygu; Erşan, Mehtap
Agraphene oxide/zirconium oxide (GO/ZrO2) nanocomposite was developed and evaluated for the efficient removal of Reactive Red120 (RR120) dye. The charac terization of the GO/ZrO2 nanocomposite was carried out by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Raman spectroscopy, Brunauer-Emmett-Teller (BET), field emission scanning electron microscopy (FESEM), and energy dispersive X-ray (EDX) spectroscopy. Box-Behnken design (BBD) was used as a statistical optimization to evaluate the effects of adsorption parameters, including adsorbent concentration, RR120 amount, and removal time. The study describes the GO/ZrO2 nanocomposite adsorbent, which has a potential application in the treatment of anionic dye-contaminated water.
Modeling the change of the sphericity feature of graphite particles ground in a ball and vibrating disc mill with grinding time
(Elsevier, 01 Eylül 2024)
Natural graphite, the most preferred battery anode material driving the EV revolution, is purified by flotation after being micronized. Therefore, grinding, an energy-intensive process that affects the size and shape of particles, is of very central importance not only for graphite ore flotation but also for the anode material preparation. Since controlling particle shape through the selection of an appropriate grinding system can enhance these processes, obtaining optimum grinding conditions by modeling the change of particle shape with grinding time can bring remarkable benefits in terms of time, energy, and cost. However, grinding modeling has mostly focused on particle size and the effect of particle shape has generally been lacking. Therefore, this study delves into the relationship between the shape of graphite particles obtained at the same size fraction by grinding them in “tumbling” and “non-tumbling” mills and the grinding time
Characterization of copper metallic particles recovered from jig separation of E-wastes
(Academia Engineering, 7 Ekim 2024)
Since copper (Cu) plays a vital role in the transition toward carbon neutrality due to its excellent electrical conductivity, environmental and economic advantages can be achieved by utilizing e-waste, which contains much more Cu metal than Cu ores. Therefore, the recovery of Cu from e-waste is crucial for ensuring sustainability and preventing the rapid depletion of natural resources. Due to the significant density difference between metals and plastics, gravity separation methods, such as jigging and shaking tables, can be efficiently applied at large scales. These methods are particularly attractive for e-waste recycling due to their low capital and operating costs. Besides, understanding e-waste materials at the particle-scale level can help improve the separation process by examining the behavior of each particle during separation. However, no literature currently examines particle shapes in the jig separation process for recovering Cu from e-waste. To fill this gap, this study explores the behavior of Cu particles in jig separation from e-waste through shape characterization of Cu particles. The fact that approximately 60% of the Cu in the feed material of the jig-heavy product consists of heavy, large, and round Cu particles shows that not only density and size are effective in stratification.
The effect of particle geometry (size & shape) on the recovery of gold and copper metallic particles from end-of-life random access memory cards by flotation
(Elsevier, 05 Mart 2024)
Since Random Access Memory (RAM), one of the main parts of computers contains a remarkable quantity of precious metals, applying flotation at the pre-concentration stage to recycle these metals can result in a more cost-effective, user-friendly, and environmentally friendly process compared to direct chemical methods. While the significance of physical characteristics like particle size and shape in the flotation process is well established, the impact of particle shape in the flotation process utilized in the recycling of end-of-life (EoL) RAMs hasn’t yet been thoroughly investigated. To fill this gap, a two-stage coarse flotation approach is used for the selective recovery of plastic and valuable metallic particles for sustainable development. The particle geometry of metallic particles recovered by flotation was characterized by axis measurement on the images by optical microscope that allows us to distinguish particles of different sizes and colors that make up the sample and evaluated in terms of particle size distribution (PSD), elongation (E) and roundness (R) parameters.
Evaluation of factors affecting tetracycline and diclofenac adsorption by agricultural soils using response surface methodology
(AICHE, 2023) GÜLER ÜLKER ASLI, TUNCEL Eliza, ERŞAN MEHTAP
The adsorption process of the pharmaceutical pollutant in the soil is affected by its physicochemical properties and soil properties. In this study, the factors affecting the adsorption of tetracycline and diclofenac onto two different soils (S and M) were investigated using response surface methodology (RSM). The RSM design was used to optimize the five variable factors (pH (2–10), contact time (5–180 min), soil amount (1–10 g/L), temperature (25–45°C)) on the adsorption of tetracycline and diclofenac. The predicted optimal conditions obtained by RSM showed that pH was the most important variable affecting the adsorption of tetracycline and diclofenac. The optimum pH for the adsorption of tetracycline and diclofenac onto the soil samples S and M were found to be 4 and 2, respectively. The adsorbed amounts of tetracycline and diclofenac onto the soils S and M were calculated to be 14.82 mg/g, 12.43 mg/g, 189.40 mg/g, and 144.81 mg/g, respectively. In addition, the effects of soil organic matter, salt, and divalent cations on the adsorption of tetracycline and diclofenac onto soils were studied. The removal of soil organic matter slightly increased tetracycline adsorption, while inhibiting diclofenac adsorption. The presence of salt and divalent cations prominently suppressed the adsorption of tetracycline and diclofenac onto soils. A possible complex mechanism was proposed for TC and DCF adsorption, including ion exchange, electrostatic interaction, and some chemical bonds.
Alkaline activation synthesis by graphite/calcite mortar and the effect of experimental conditions on compressive strength
(Springer, 20.07.2023) Kütük, Nurşah; Çetinkaya Gürer, Sevil
The construction industry is an application area that has continuity all over the world and requires cheap, durable, and environmentally friendly materials. Synthesis with alkali activation includes materials that have come to the fore in the construction industry in recent years. In this study using alkali activation method, a graphite/calcite mortar was prepared by optimizing the experimental conditions and its properties were investigated. The effects of Na2SiO3/NaOH mass ratio, NaOH solution concentration, and graphite content variables on structure and compressive strength in alkaline activation synthesis were investigated. It was determined that the samples reached a compressive strength of 21 MPa at the end of 28 days when the Na2SiO3/NaOH ratio was 2 and the NaOH concentration was 10 M. In the continuation of the optimized experimental conditions, the effect of the amount of graphite on the compressive strength was examined between 5 and 100% (w/w). Structural properties of the samples were investigated by X-ray diffraction and Fourier transform infrared spectroscopy, and their morphological properties were investigated by scanning electron microscopy. It was determined that C–S–H gel was formed and samples with heterogeneous morphology were synthesized.
Symbolic regression with feature selection of dye biosorption from an aqueous solution using pumpkin seed husk using evolutionary computation-based automatic programming methods
(Elseiver, 30.11.2023) Arslan, Sibel; Kütük, Nurşah
Industrial waste pollution is a serious and systematic problem that harms the environment and people. The development of cheap, simple, and efficient techniques to solve this problem is important for sustainability. In this study, both experimental and evolutionary computation (EC)-based automatic programming (AP) methods were used to investigate the biosorption process for water treatment. In the experiments, titan yellow (TY), an anionic dye, was biosorbed from an aqueous solution containing pumpkin seed husk (PSH). The structure of PSH was examined using a Fourier transform infrared spectroscopy (FTIR) and a scanning electron microscope (SEM). The result of the experimental studies was that TY biosorption of PSH reached a biosorption efficiency of 95% after 120 min of contact time. The maximum biosorption capacity ( ) was calculated to be 181.8 mg/g. It was found that the biosorption of TY better followed the Dubinin–Radushkevich isotherm ( ) and pseudo second-order reaction kinetics ( ). Based on the thermodynamic data, the biosorption process was exothermic and spontaneous. After the experiments, the process was modeled using pH, biosorbent concentration, initial dye concentration, contact time, and temperature as inputs and biosorption efficiency (%) as output for the methods. Moreover, the success of these AP methods was compared with a newly proposed evolutionary method. The simulation results indicate that AP methods generate best models ( and ). At the same time, the most important parameter of the process in the feature analysis is contact time. This study shows that EC-based AP methods can effectively model applications such as the biosorption process.
Reduction of Graphene Oxide using purple cabbage extract and investigation of photocatalytic activity by oxidation
(Gazi Üniversitesi, 06.01.2023) Kütük, Nurşah; Boran, Filiz; Çetinkaya Gürer, Sevil
Graphene and its derivatives are an important material with many unique properties and potential in photocatalytic degradation and adsorption applications. Removal of oxygen-containing functional groups by reduction of graphene oxide (GO) is an interesting method that has been used frequently in recent years. The aim of this study is to examine graphene oxide reduction by using green synthesis and purple cabbage aqueous extraxt, which is an easy and effective method, and its use in photocatalytic removal applications. To optimize the synthesis conditions, the reaction temperature was first studied at 25, 50, and 100, and then the reaction time was studied for 1, 2, 4, and 6 hours. According to XRD, FTIR, UV/vis and SEM results, suitable experimental conditions for GO reduction are obtained at reaction temperature of 100 and reaction time of 6 h. The obtained reduced graphene oxide (IGO) was used in photocatalytic degradation experiments in the aqueous solution of methylene blue (MM), an organic and cationic dye, under UV lamp and in the presence of H2O2. The results showed that after 120 min, IGO removed 85% of MM from the aqueous solution. It was determined that the MM photocatalytic degradation reaction kinetics of IGO matched the pseudo second-order reaction kinetics.
Investigation of structural, morphology, and conduction mechanism of GO–Fe3O4–TiO2 composite material
(2023) Ateş, Ayten; ben brahim, Khawla; Keklikcioğlu Çakmak, Neşe; Oueslati, Abderrazek; Gargouri, Mohamed
The graphene oxide composite (GO), iron oxide (Fe3O4), and titanium dioxide (TiO2) were prepared by the sol–gel process. The surface of GO is coated with TiO2 and Fe3O4 nanoparticles, and the composite contains 10.26% C, 23.70% O, 57.17% Ti, and 8.87% Fe. The formation of anatase TiO2 and magnetite Fe3O4 on the surface of GO was detected by XRD and Raman analysis. The N2 adsorption–desorption isotherm and pore size distribution results showed the formation of a mesoporous material with a specifc surface area of 233.3 m2 /g, a total pore volume of 0.298 cm3 /g, and an average pore diameter of 7.7 nm. The GO–Fe3O4– TiO2 composite’s dielectric characteristics were examined in the frequency and temperature ranges of 0.1 Hz–5 MHz and 293–373 K, respectively. The Nyquist plot suggests the non-Debye conduction behaviour, which may be related to the distribution of relaxation times within the composite material. The contribution of grains and grain boundaries to the total conductivity is confrmed by impedance spectroscopy. Jonscher’s power law was used to examine AC conductivity graphs, and the variation in the exponent “s” revealed that CBH models accurately characterize the conduction mechanism in the composite. The dielectric measurements reveal Maxwell–Wagner polarization and a thermal-activated relaxation process.
Experimental and density functional theoretical analyses on degradation of acid orange 7 via UV irradiation and ultrasound enhanced by Fenton process
(05.04.2023) Yıldız, Sayiter; Topal Canbaz, Gamze; Kaya,Savaş; Maslov, Mikhail M.
In this study, Acid Orange 7 (AO7) removal from synthetic water by advanced oxidation processes was investigated. Within the scope of the study, individual and different integrated applications of Fenton reaction, photooxidation and sonication were examined. The effects of variables such as H2O2, Fe2+, reaction time, pH and initial dye concentration on the removal performance were investigated. Three different UV light sources, namely UV-A, UV-B and UV-C, were used. In order to study the effect of ultrasound addition, ultrasound with a frequency of 40 kHz and a power of 180 W was used. Effective AO7 degradation was achieved by Fenton oxidation at optimum conditions of 100 mg L−1 H2O2, 25 mg L−1 Fe2+, 100 mg L−1 dye concentration, 3 pH and 30 min. The removal efficiency of the Fenton process was 97.6%, while it was for Fenton/UV-A, UV-B and UV-C light 97.6%, 96.97% and 97.35%, respectively. In the Fenton/US/UV process with ultrasound addition, removal efficiencies of 97.45%, 97.52% and 95.95% were obtained in UV-A, UV-B and UV-C lights, respectively. In Fenton/US process, the removal efficiency was 96.35%. In addition, in the kinetic study, it was determined that each process complied with the zeroth-order kinetics with the highest R2 values. This study is especially important in terms of demonstrating the synergistic effect of these processes in an integrated reactor. Moreover, in such studies, the chemical reactivity analysis of the studied dye is quite important. For this aim, Density Functional Theory (DFT) calculations were performed. The study showed that Fenton processes can be used as an efficient and reliable method for AO7 removal. In this study, the experimental results for AO7 degradation were supported by theoretical calculations.
Density Functional Theory Computations and Experimental Analyses to Highlight the Degradation of Reactive Black 5 Dye
(08.08.2023) Yıldız, Sayiter; Topal Canbaz, Gamze; Kaya,Savaş; Maslov, Mikhail M.
The oxidative degradation of Reactive Black 5 (RB5) in aqueous solution was investigated using Fenton (FP), photo Fenton (P-FP), sono Fenton (S-FP), and sono photo Fenton (S-P-FP) processes. Degradation experiments showed efficient dye degradation for FP, P-FP, S-FP, and S-P-FP under optimal conditions. The half-life values of the reaction calculated for first-order reaction kinetics showed that the S-FP process is faster than the FP and P-FP processes. Using DFT calculations, the chemical reactivities of the studied chemical systems were analyzed. Especially the calculated chemical hardness values reflect the reactivities of the dye and the dye-Fe2+ complex. The calculated binding energy between the Fe2+ ion and RB5 of 15.836 eV is compatible with the prediction made in the light of the principle of hard and soft acids and bases. The computed data supported the experimental observations.
Fe3O4@Granite: A Novel Magnetic Adsorbent for Dye Adsorption
(07.09.2023) Topal Canbaz, Gamze
Magnetic granite (MG), a new and low-cost adsorbent, was prepared by the chemical co-precipitation of Fe2+ and Fe3+ using granite (G), which is a magmatic rock type. The adsorption of the Reactive Black 5 (RB5) dye from aqueous solutions on Fe3O4-modified granite was examined in a batch system. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), X-ray fluorescence spectrometry (XRF), X-ray diffractometry (XRD), N2 adsorption–desorption, vibrating-sample magnetometry (VSM), and point-of-zero charge (pHpzc) analysis were used to characterize the prepared MG. Magnetic granite displayed significant magnetization and could be easily separated using external magnets. The maximum adsorption capacity was 29.85 mg/g at 298 K. According to kinetic and isothermal examinations, the pseudo-second-order model and Langmuir isothermal adsorption were the best fit for adsorption. It was found that the enthalpy change ΔH (kJ/mol) was −31.76, and the entropy change ΔS (kJ/mol) was 0.096 for a temperature change of 298–330 K. The ΔG° (kJ/mol) value was negative at all temperatures (298 K, −2.86 kJ/mol; 303 K, −2.85 kJ/mol and 313 K, −1.50 kJ/mol), indicating that the adsorption of RB5 on MG was spontaneous.
Doxorubicin and tamoxifen loaded graphene oxide nanoparticle functionalized with chitosan and folic acid for anticancer drug delivery.
(February 2023) Keklikcioğlu Çakmak, Neşe; Eroğlu, Atakan
Research has commonly utilized graphene-based drug delivery systems for a long time to achieve efective cancer treatment. In the present study, doxorubicin (DOX) and selective estrogen receptor modulator tamoxifen (TAM) anticancer drugs used in breast cancer treatment were bound to a graphene oxide (GO)-based and folic acid (FA)-targeted nanocarrier system that was made biocompatible with chitosan (CS). To this end, graphene oxide synthesis was primarily carried out by employing the modifed Hummer’s method, and then FA and CS were loaded on GO to obtain a targeted and biocompatible carrier The characterization of the obtained conjugate was performed by X-ray difraction analysis, Fourier transform infrared spectroscopy, UV-visible spectrophotometry, scanning electron microscopy, and zeta potential analysis. The zeta potential values of all samples were checked and all of them have a zeta potential above the stability value of±25 mV. GO-CS-FA has the highest zeta potential of 68.8 mV. The graphene oxide-chitosan-folic acidtamoxifen-doxorubicin (GO-CS-FA-TAM-DOX) nanocarrier-based drug displayed a pH-dependent drug release. The drug release profle from these systems was researched in two pH bufer solutions prepared as acidic (pH 5.8) and physiological (pH 7.4). The characterization analyses showed that the drugs bound successfully to the targeted delivery system. The drug release analyses demonstrated that GO-CSFA-TAM-DOX was released better in the acidic (pH 5.8) medium compared to the physiological (pH 7.4) medium after 24 h.
Nitrogen-doped graphene quantum dots/co-doped PANI binary nanocomposites as high-performance supercapacitor electrode materials
(2023) Getiren, Bengü; Altınışık, Hasan; Çıplak, Zafer; Soysal, Furkan; Yıldız, Nuray
In this paper, a suitable and high-performance electrode material for practical applications was developed using a simple two-step approach. Here, we report that nitrogen-doped graphene quantum dots with co-doped polyaniline (N-GQDs-PANI) were fabricated by in situ polymerization as supercapacitor electrodes and that the effect of the amount of N-GQDs in the electrode material on the electrochemical performance was investigated. The integration of N-GQDs into co-doped PANI structure prevented the agglomeration of PANI and enabled the fabrication of N-GQDs as thin film on the surface. This modification improved the charge transfer of the N-GQDs- PANI electrode compared to N-GQDs and pure PANI electrodes, allowing it to exhibit superior electrochemical performance. The N-GQDs-PANI electrode has a specific capacitance of 503 F/g at a current density of 5 A/g with a capacitance retention of about 91.9 % after 10000 charge/discharge cycles.
Graphene oxide/polyaniline/silver nanocomposite synthesis and photothermal performance
(2023) Yürekli Bayar, Elif; Getiren, Bengü; Soysal, Furkan; Çıplak, Zafer; Yıldız, Nuray; Bayraktar, Emine
In this study, synthesis and characterization of graphene oxide-polyaniline-Ag nanocomposites (GO-PANI-Ag) as a photothermal agent are demonstrated. In situ polymerization process was used to prepare the ternary nanocomposite of graphene oxide, aniline, and Ag nanoparticles. The chemical and structural characteristics of the nanocomposites were investigated by UV–Vis, FTIR, Raman, XRD, SEM, and TEM and photothermal properties were examined in the NIR region. 1 mL of aqueous dispersions of the nanocomposites at various concentrations were irradiated with the 808 nm NIR laser at 1.5, 2.0, and 2.5 W cm 2 laser power densities. The temperature of GO-PANI4-Ag0.25 nanocomposite increased to 66.6, 80.1 and 90.6 ◦C at 1.5, 2.0, and 2.5 W cm 2 of power density at 0.1 mg mL 1 for 5 min, respectively. The results showed that the GO-PANI-Ag nanocomposite has excellent photothermal performance and high stability. The synthesized nanocomposite could be used as an antibacterial agent or in cancer therapy.
Preparation, Characterization, and Application of Metal Oxide- Doped Zeolitic Imidazolate Framework
(2023) Kümbetlioğlu, Fulya; Oskay, Kürşad Oğuz; Çıplak, Zafer; Ateş, Ayten
Metal−organic frameworks (MOFs) attract the attention of researchers due to their unique properties, such as high surface area, porosity, and stability. Therefore, in this study, the synthesis of zeolitic imidazole frameworks (ZIF-8), a subclass of MOFs, and copper oxide (Cu2O) and manganese oxide (MnO2) containing ZIF-8 was carried out by a mixing method with methanol. The characterization results show that the polyhedral structure of ZIF-8 was prepared with a surface area of 2088 m2/g and a crystallite size of 43.48 nm. Then, each and mixture of two metal oxides were introduced into the ZIF-8 crystal structure. It was found that the surface area and pore volumes of all metal/ZIF- 8 samples decreased with metal loading, depending on the type and ratio of metal oxides. The ZIF-8 containing 4.0 wt % Cu2O and 1.0 wt % MnO2 had the highest surface area (2084 m2/g), which was closest to that of ZIF-8. The polyhedral structure was maintained by the addition of both metal oxides, and the crystal size of the material decreased with the loading of MnO2 to the ZIF-8 structure. All of the synthesized samples were analyzed in supercapacitor applications and a relatively higher value of specific capacitance was obtained for Cu−Mn/ZIF-8 due to higher surface area and improved conductivity. In addition to supercapacitor applications, the properties of metal/ZIF-8 are also promising for applications such as catalysts, membranes, and gas storage.
Ag@Fe3O4 nanoparticles decorated NrGO nanocomposite for supercapacitor application
(2023) Çıplak, Zafer; Yıldız, Nuray
There is still a great need for production and design of electrode materials with superior electrochemical properties for supercapacitor application. Nanocomposites containing graphene-based metal-metal oxide nanostructures are promising electrode materials because of their high conductivity, excellent surface properties, and effective charge storage with both EDLC and pseudocapacitance mechanisms. In this study, Ag@Fe3O4 core@shell nanoparticles decorated nitrogen doped reduced graphene oxide (NrGO) was obtained with a facile and simple method. On the surface of NrGO nanosheets, Ag nanoparticles were found to be coated with Fe3O4 nanoparticles with a particle size of 5–12 nm. The electrochemical measurements of NrGO-Ag@Fe3O4 nanocomposite were carried out in a two-electrode cell. The ternary nanocomposite exhibited 212.2 F/g specific capacitance at a current density of 1 A/g, as well as high cyclic stability, the NrGOAg@ Fe3O4 nanocomposite retained 77 % of its specific capacitance after 10,000 cycles. The Ag@Fe3O4 decorated NrGO nanocomposite indicates great potential as an electrode material for supercapacitor applications.

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