Browsing by Author "Ulas, Berdan"

Now showing 1 - 20 of 42

Application of Ann and Rsm for Rhodamine B and Safranine-O Decolorization on Zinc-Carbon Battery Waste Derived Ag/Cofe-ldh Catalyst
(Amer Chemical Soc, 2024) Ecer, Umit; Ulas, Berdan; Yilmaz, Sakir
The present work is first aimed at recovering graphite from carbon rods of waste zinc-carbon (Zn-C) batteries for applications such as wastewater treatment, in order to contribute to the development of a sustainable environment. Then, a composite material, cobalt-iron layered double hydroxide combination with reduced graphene oxide, and with subsequent Ag nanoparticles deposition via NaBH4 reduction method (Ag/CoFe-LDH/rGO) was prepared for the catalytic activity of Rhodamine B (RhB) and Safranine-O (SO) as model contaminants from aquatic media. The catalytic activity of RhB and SO by Ag/CoFe-LDH/rGO in the presence of NaBH4 was studied to model and optimize the process parameters (NaBH4 amount, reaction time, initial dye concentration (C-o), and catalyst dosage) via central composite design (CCD)-response surface methodology (RSM). Also, an artificial neural network (ANN) model was developed to estimate the catalytic activity of each dye using an RSM data set. The catalytic activities of 99.54% and 99.96% were obtained for RhB and SO dyes, respectively, under the optimal conditions: NaBH4 amount 12.32 mM, reaction time 3.19 min, C-o 33.46 mg/L, and catalyst dosage 1.24 mg/mL for RhB dye; NaBH4 amount 16.76 mM, reaction time 3.06 min, C-o 15.10 mg/L, and catalyst dosage 1.46 mg/mL for SO dye. The optimum conditions of process parameters by ANN with gray wolf optimizer (GWO) were in good agreement with the points determined the RSM-CCD. These results demonstrate that RSM and ANN approaches can be applied practically and efficiently to maximize the catalytic activity of RhB and SO by Ag/CoFe-LDH/rGO in the existence of NaBH4. On the other hand, from the kinetic and thermodynamic studies, the positive activation enthalpy, Delta H-# and the negative activation entropy, Delta S-# values for each dye demonstrated that the catalytic performance was endothermic and less random at the solid/liquid interface.
Atomic Molar Ratio Optimization of Carbon Nanotube Supported Pdauco Catalysts for Ethylene Glycol and Methanol Electrooxidation in Alkaline Media
(Springer international Publishing Ag, 2019) Ulas, Berdan; Caglar, Aykut; Kivrak, Arif; Kivrak, Hilal
In this study, carbon nanotube supported Pd, PdAu, and PdAuCo electrocatalysts (Pd/CNT, PdAu/CNT, and PdAuCo/CNT) were synthesized via NaBH4 reduction method at varying molar atomic ratios to investigate their performance for methanol and ethylene glycol electrooxidation in alkaline media. The characterization of the as-prepared catalysts was performed using X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, N-2 adsorption-desorption, and small-angle X-ray-scattering analysis. From the physical characterization results, it was seen that PdAuCo/CNT catalysts were successfully prepared. X-ray photoelectron spectroscopy results showed that Pd and Au atoms employed in the preparation of the catalysts exist mainly in their elemental state. X-ray diffraction results indicated the formation of a new phase. Furthermore, the mean particle size of Pd50Au30Co20/CNT was determined as 7.9 and 8.7nm using small-angle X-ray scattering and transmission electron microscopy analyses. Pd50Au30Co20/CNT demonstrated the type V adsorption isotherms with H1-type hysteresis, which indicates the mesoporous structure of the catalyst. Electrocatalytic activity of the catalysts for ethylene glycol and methanol electrooxidation was investigated with cyclic voltammetry and electrochemical impedance spectroscopy. The electrocatalytic activity of Pd50Au30Co20/CNT was determined as 262 and 694mA/mg Pd for methanol and ethylene glycol electrooxidation. In accordance with cyclic voltammetry and electrochemical impedance spectroscopy results, Pd50Au30Co20/CNT possesses the highest electrocatalytic activity for both electrooxidation.
Biosorption of Remazol Orange Rr From Aqueous Solution: Kinetic, Equilibrium and Thermodynamic Studies
(desalination Publ, 2019) Ulas, Berdan; Ergun, Mubeccel
Remazol Orange RR ( RORR) is one of the most frequently used textile dye which causes environmental pollution. In the present study, parameters affecting the RORR biosorption with dead Saccharomyces cerevisiae yeast were investigated. The maximum %RORR removal was found to be 84.9% at 2 g/L biosorbent dosage, 200 mg/L initial dye concentration, pH 3.0, and 25 degrees C. RORR biosorption with S. cerevisiae was expalined by pseudo-second-order kinetics model and Langmuir adsorption isotherm with correlation coefficient ( R-2) of 0.99 and 0.87, respectively. The enthalpy change (Delta H), entropy change (Delta S) and activation energy ( E-a) were determined as 35.9 kJ/mol, 88.1 kJ/mol K and 3.36 kJ/mol, respectively. In addition, Gibbs free energy change was calculated as -10.04, -8.03 and -8.33 kJ/mol for 298, 308 and 318 K, respectively. It is concluded that the biosorption of RORR by S. cerevisiae occurs mainly by physical adsorption through a spontaneous process. The high dye removal and biosorbent capacity indicated that S. cerevisiae is a promising biosorbent for dye removal.
Carbon Monoxide and Formic Acid Electrooxidation Study on Au Decorated Pd Catalysts Prepared Via Microwave Assisted Polyol Method
(Taylor & Francis inc, 2019) Ulas, Berdan; Kivrak, Arif; Aktas, Nahit; Kivrak, Hilal
In this study, carbon supported Pd monometallic and PdAu bimetallic catalysts are prepared by using microwave assisted polyol method to investigate their carbon monoxide and formic acid electrooxidation activities. These catalysts are characterized by using Scanning Electron Micrsocopy (SEM-EDX) and N-2 adsorption desorption measurements. EDX measurements reveal that catalysts are prepared at desired ratios. The electrochemical characterization was performed via cyclic voltammetry and CO stripping voltammetry. Electrochemical surface area (ECSA) was calculated thanks to CO oxidation peaks. It was reported that CO tolerance and ECSA of the PdAu/C catalysts were higher than that of the Pd/C, attributed to sweeping effect of Au particles in terms of CO adsorption. Furthermore, formic acid electrooxidation activity of these catalysts are examined by using cyclic voltammetry (CV). PdAu/CNT catalyst at prepared at 90:10 Pd:Au ratio exhibited the highest formic acid electroxidation activity. It is clear that PdAu/CNT catalyst is a promising catalyst for CO and formic acid electrooxidation. [GRAPHICS] .
A Comparative Analysis for Anti-Viral Drugs: Their Efficiency Against Sars-Cov
(Elsevier, 2021) Kivrak, Arif; Ulas, Berdan; Kivrak, Hilal
Coronavirus, known as the coronavirus pandemic, is continuing its spread across the world, with over 42 million confirmed cases in 189 countries and more than 1.15 million deaths. Although, scientists focus on the finding novel drugs and vaccine for SARS-CoV-2, there is no certain treatment for it. Antiviral drugs such as; oseltamivir, favipiravir, umifenovir, lopinavir, remdesivir, hydroxychloroquine, chloroquine, azithromycin, ascorbic acid, corticosteroids, are mostly used for patients. They prevent cytokine storm that is the main reason of deaths related to SARS-CoV-2. In addition, anti-inflammatory agents have critical roles to inhibit the lung injury and multisystem organ dysfunction. The combination with anti-viral drugs with other drugs displays high synergistic effects. In the present study, the drugs used for Covid-19 are analyzed and compare the efficiency for the Covid-19 patients from the different continents including USA, South Korea, Italy, Spain, Germany, Russia, Brazil, Turkey, and China. Nowadays, all countries tried to find vaccine and new drug candidates for SARS-CoV-2, but anti-viral drugs may be the best candidates for the treatment of Covid-19 before finding novel anti-Covid drug.
Composition Dependent Activity of Pdagni Alloy Catalysts for Formic Acid Electrooxidation
(Academic Press inc Elsevier Science, 2018) Ulas, Berdan; Caglar, Aykut; Sahin, Ozlem; Kivrak, Hilal
In the present study, the carbon supported Pd, PdAg and PdAgNi (Pd/C, PdAg/C and PdAgNi/C) electrocatalysts are prepared via NaBH4 reduction method at varying molar atomic ratio for formic acid electrooxidation. These as-prepared electrocatalysts are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), inductively coupled plasma mass spectrometry (ICP-MS), N-2 adsorption desorption, and X-ray electron spectroscopy (XPS), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), chronoamperometry (CA), and lineer sweep voltammetry (LSV). While Pd-50,Ag-50/C exhibits the highest catalytic activity among the bimetallic electrocatalyst, it is observed that Pd70Ag20Ni10/C electrocatalysts have the best performance among the all electrocatalysts. Its maximum current density is about 1.92 times higher than that of Pd/C (0.675 mA cm(-2)). Also, electrochemical impedance spectroscopy (EIS), chronoamperometry (CA) and lineer sweep voltammetry (LSV) results are in a good agreement with CV results in terms of stability and electrocatalytic activity of Pd50Ag50/C and Pd70Ag20Ni10/C. The Pd70Ag20Ni10/C catalyst is believed to be a promising anode catalyst for the direct formic acid fuel cell. (C) 2018 Elsevier Inc. All rights reserved.
Constructing Hnt-Ac Supported Coni Nanoparticles for Hydrogen Generation Toward Nabh4 Hydrolysis: Optimization With Rsm-Ccd
(Springer, 2024) Ecer, Umit; Yilmaz, Sakir; Ulas, Berdan; Kaya, Sefika
In this study, activated carbon (AC) obtained from waste hazelnut shell and halloysite nanotube (HNT) were used to prepare HNT-AC support material by hydrothermal method. CoNi/HNT-AC catalyst was synthesized by reducing Co and Ni on HNT-AC by chemical reduction method. CoNi/HNT-AC has been characterized using scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), N-2 adsorption-desorption, elemental mapping, and transmission electron microscopy (TEM) methods. The optimum reaction conditions for hydrogen generation through NaBH4 hydrolysis on CoNi/HNT-AC catalyst were determined using response surface methodology (RSM). The proposed quadratic model for NaBH4 hydrolysis on CoNi/HNT-AC was found to be statistically significant with a correlation coefficient of 0.96. Under the optimum reaction conditions of 40.76 mg catalyst, 0.18 M NaBH4, and 8.64 wt% NaOH, the hydrogen generation rate (HGR) and activation energy (E-a) were obtained as 1114.16 mL/gcat. min. and 24.15 kj/mol, respectively.
Design of 2-(4 Based Remarkable Organic Catalyst Towards Hydrazine Electrooxidation
(Elsevier Science Sa, 2021) Er, Omer Faruk; Ulas, Berdan; Ozok, Omruye; Kivrak, Arif; Kivrak, Hilal
Herein, 2-(4-(2-pentyllbenzo[ b]thiophen-3-yl)benzylidene)malononitrile (6B) is synthesized by using coupling reactions, electrophilic cyclization reactions, and condensation reactions. Then, these materials are employed as anode catalysts for hydrazine electrooxidation reactions with electrochemical methods such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in 1 M KOH + 0.5 M N2H4 solution on different benzothiophene derivates. 6B catalyst exhibits the best catalytic activity in hydrazine electrooxidation reaction with 3.22 mA cm(-2) (16.72 mA mg(-1) 6B) value. Thus, for the electrodes obtained from 6B, the electrode preparation stage is optimized by the response surface methodology (RSM) and the hydrazine electrooxidation current under optimum conditions is found as 4.95 mA cm(-2). EIS results reveal that 6B modified electrode has the lowest charge transfer resistance. In conclusion, 6B catalyst could be used as anode catalysts in hydrazine fuel cells instead of expensive catalysts such as Pt, Pd, and Au.
Determination of Optimum Pd:ni Ratio for Pdxni100-x/Cnts Formic Acid Electrooxidation Catalysts Synthesized Via Sodium Borohydride Reduction Method
(Wiley, 2019) Ulas, Berdan; Caglar, Aykut; Kivrak, Hilal
The main purpose of this study is to investigate the optimum Pd:Ni molar ratio for carbon nanotube-supported PdNi (PdxNi100-x/CNT) alloy catalysts toward formic acid electrooxidation (FAE). NaBH4 reduction method was employed for the synthesis of Pd90Ni10/CNT, Pd70Ni30/CNT, Pd50Ni50/CNT, and Pd40Ni60/CNT. Synthesized catalysts were characterized by employing advanced surface analytical techniques, namely, X-ray diffraction (XRD), transmission electron microscopy (TEM), N-2 adsorption-desorption, and inductively coupled plasma-mass spectrometry (ICP-MS). The characterization results showed that all catalysts were successfully synthesized at desired molar composition. Pd90Ni10/CNT displayed the highest specific and mass activities with 2.32 mA/cm(2) and 613.9 mA/mg Pd, respectively. Specific activity of the Pd90Ni10/CNT was found approximately 3.6, 2.3, 11.1, and 3.4 times higher than those of Pd70Ni30/CNT, Pd50Ni50/CNT, Pd40Ni60/CNT, and Pd/CNT, respectively. The synergistic effect between Pd and Ni at optimized metal ratio was utilized to obtain an improvement in specific activity. Furthermore, Pd90Ni10/CNT showed the lowest charge transfer resistance (R-ct) and a long-term stability. To our knowledge, this is the first study reporting the optimization of atomic molar composition for PdxNi100-x/CNT catalysts toward FAE.
Development of Effective Bimetallic Electrocatalysts for Glucose Electrooxidation
(Electrochemical Soc inc, 2022) Ulas, Berdan; Yilmaz, Yonca; Kivrak, Hilal; Erunal, Ebru
Vulcan XC-72 supported PdCo and PtCo electrocatalysts were synthesized via supercritical deposition method and designed as anode catalyst for direct glucose fuel cells (DGFCs). As-prepared electrocatalysts were characterized by using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), inductively coupled plasma-mass spectrometer (ICP-MS), scanning electron microscopy energy-dispersive X-ray spectroscopy (SEM-EDX), and transmission electron microscopy (TEM) while electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and chronoamperometry (CA) methods were used for the electrochemical characterization of PdCo/Vulcan XC-72 and PtCo/Vulcan XC-72 catalysts. PdCo/Vulcan XC-72 anode catalyst showed higher electrocatalytic activity for glucose electrooxidation than PtCo/Vulcan XC-72. In addition, chronoamperometry results showed that PdCo/Vulcan XC-72 possessed better stability within 1000 s than PtCo/Vulcan XC-72. The improvement in electrocatalytic activity and stability has been attributed to the alteration of the electronic properties of Pd with the addition of Co. The PdCo/Vulcan XC-72 catalyst is a good candidate for use as an anode catalyst in DGFCs. (C) 2022 The Electrochemical Society ("ECS"). Published on behalf of ECS by IOP Publishing Limited.
Development of Nonenzymatic Benzoic Acid Detection on Pdsn/Gce Xc-72r Prepared Via Polyol Method
(Wiley-v C H verlag Gmbh, 2019) Kazici, Hilal Celik; Yayla, Muge; Ulas, Berdan; Aktas, Nahit; Kivrak, Hilal
In this study a PdSn based sensor was developed for the determination of benzoic acid (BA) in foods. A carbon (Vulcan XC-72R) supported PdSn catalyst was prepared via polyol method and its surface electronic and chemical properties were investigated by advanced surface analytical techniques such as scanning electron microscopy (SEM), X-ray diffraction spectroscopy (XRD), X-ray Photoelectron Spectroscopy (XPS), temperature-programmed reduction with H-2 (TPR-H-2) and transmission electron microscopy (TEM). Electrochemical measurements were performed by employing cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques on PdSn/GCE/Vulcan XC-72R electrode. The developed sensor showed a wide linear range up to 10 mM with a 0.77 mu M low limit of detection (LOD) as well as high stability. Further experiments were performed on food samples containing BA to achieve real sample measurements. For real sample measurements, PdSn/GCE/Vulcan XC-72R electrode was used for the determination of BA in different kinds of samples such as mayonnaise, ketchup and carbonated beverages.
The Development of Titanium Dioxide Nanotube-Supported Cdte Catalysts for Photocatalytic Enzymatic Glucose Fuel Cell and Response Surface Methodology Optimization
(Elsevier Science Sa, 2024) Caglar, Aykut; Pelen, Yucel Tuncbora; Ulas, Berdan; Zahmakiran, Mehmet; Kivrak, Hilal
Energy is one of the critical needs for human life and well-being. Alternative energy sources are essential due to the increase in energy demand with the rise in population the development of industrialization, and the damage caused by fossil fuels to the environment. Fuel cells, an alternative energy source, are a clean and environmentally friendly technology that converts chemical energy into electrical energy. In this study, titanium dioxide (TiO 2 ) nanotube (TNT)-support CdTe catalysts were synthesized by the wet impregnation (WI) method. Glucose oxidase (GOD) and laccase (LAC) enzymes were modified by incubation on CdTe/TNT catalysts. These enzymatic and non-enzymatic catalysts were characterized by scanning electron microscope-energy dispersive X-ray (SEMEDX) and mapping, X-ray diffraction (XRD), Raman spectroscopy, and transmission electron microscope (TEM) analyses. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and chronoamperometry (CA) analyses were used to examine the activity, resistance, and stability of catalysts for enzymatic photocatalytic glucose electrooxidation. The 3 % CdTe(50-50)-TNT-GOD/GCE electrode exhibited the highest activity, resistance, and stability under UV illumination compared to other electrodes. The modification parameters of the electrodes, incubation time, amount of catalyst ink, and drying time were found to be 136.96 min, 8.94 mu L, and 21.30 min with response surface method (RSM) analysis, respectively. The estimated specific activity value was obtained as 0.754 mA/cm 2 under optimized conditions.
Disentangling the Enhanced Catalytic Activity on Ga Modified Ru Surfaces for Sodium Borohydride Electrooxidation
(Elsevier, 2021) Ulas, Berdan; Alpaslan, Duygu; Yilmaz, Yonca; Dudu, Tuba Ersen; Er, Omer Faruk; Kivrak, Hilal
Herein, multi walled carbon nanotube (MWCNT) supported RuGa nanocatalysts (RuGa/MWCNTs) are synthesized at varying atomic molar ratio via sodium borohydride (SBH) reduction method toward SBH electrooxidation (SBHE) and SBH hydrolysis (RSBH). From the X-ray diffraction (XRD) results, Ru and Ga metals are found to be in the alloy form and the average crystal size is determined as 2.77 nm. The distribution of RuGa particles on MWCNT is confirmed using SEM-EDX. These nanocatalysts were employed for RSBH and further measurements were performed to investigate their SBHE activity. For RSBH for RuGa/MWCNT nanocatalysts, one could note that Ga addition to Ru enhanced the initial rate, H-2 generation rate, and turnover frequency values and Ru99Ga1/MWCNT has the highest initial rate, H-2 generation rate, and turnover frequency value. According to the cyclic voltammetry (CV) results of the prepared RuGa/MWCNT nanocatalysts, Ru99Ga1/ MWCNT show the highest electrocatalytic activity for SBHE and this result is in line with the results of electrochemical impedance spectroscopy (EIS). In addition, chronoamperometric curves indicate that Ru99Ga1/MWCNT possesses long term stability compared to these of other nanocatalysts. Catalytic RSBH results of Ru99Ga1/MWCNT show that this nanocatalyst is more active than others. As a result, it is clear that RuGa/ MWCNT is a promising nanocatalyst for fuel cells.
Enhanced Hydrogen Production Via Methanolysis and Energy Storage on Novel Poplar Sawdust-Based Biomass-Derived Activated Carbon Catalyst
(Springer, 2023) Kaya, Sefika; Saka, Ceren; Yildiz, Derya; Erol, Salim; Ulas, Berdan; Demir, Izge; Kivrak, Hilal
The originality of our current work is based on the use of H3PO4 functionalized waste poplar sawdust as a supercapacitor electrode material and catalyst for NaBH4 methanolysis reaction. N-2 adsorption-desorption, scanning electron microscopy with energy-dispersive X-ray spectrometry (SEM-EDX), Fourier-transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD) are utilized for characterization of the activated carbon (AC). In the first stage of our study, the effect of H3PO4 ratios and carbonization temperature on the hydrogen generation rate (HGR) is investigated and optimized. The optimum H3PO4 and carbonization temperature for NaBH4 methanolysis on AC are determined as 4:1 and 600 & DEG;C, respectively. The optimum points for the methanol concentration, NaBH4 concentration, reaction temperature, and catalyst amount affecting the HGR values for the methanolysis reaction on the KV4-600 catalyst under these conditions are determined as 4 ml, 1.25 wt% NaBH4, 60 & DEG;C, and 50 mg, respectively. Moreover, the HGR, activation energy, and the reaction completion duration under optimized reaction conditions are obtained as 19,050.00 mL min(-1) g(cat)(-1), 11.76 kJ mol(-1), and 60 s, respectively. The performance of the KV4-600 as a supercapacitor electrode material is evaluated by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS). The specific capacitance of the KV4-600 at a specific current of 0.25 A g(-1) is found to be 161.15 F g(-1). KV4-600 shows satisfactory results both as supercapacitor electrode material and as catalyst for NaBH4 methanolysis. [Graphics]
Evaluation of Metal-Organic Framework/Layered Double Hydroxide-Embedded Sodium Alginate Beads for Effective Removal of Tartrazine Dye: a Comparative Analysis of Rsm and Ann
(Elsevier, 2025) Yilmaz, Sakir; Ecer, Umit; Ulas, Berdan; Yagizatli, Yavuz
NiFe-layered double hydroxide supported metal-organic framework-embedded alginate bead composite (MIL-88 A/NiFe-LDH@SA) was developed and investigated for the removal of tartrazine food dye (TTZ). Structural characterizations of MIL-88 A/NiFe-LDH@SA were determined by the measurement of FTIR, XRD, BET, SEM, and EDX. Response surface methodology (RSM) and artificial neural network (ANN) were applied to predict the removal of TTZ dye. The optimization of the relevant parameters was obtained via the central composite design (CCD) in RSM. The numerical optimization revealed that a maximum removal efficiency of 94.82 % was achieved at Co of 8.02 mg/L, pH of 3.74, adsorption duration of 4.72 h, and adsorbent amount of 1.33 mg/mL. A comparative analysis was also performed for RSM and ANN models. The findings show that both models can accurately predict TTZ removal efficiency. However, based on the statistical analysis results, ANN demonstrated a higher level of accuracy than RSM in predicting TTZ removal. The kinetic studies also revealed that the adsorption well obey the pseudo-second order (PSO). The isotherm studies indicated that the LangmuirFreundlich (L-F) model was proper for explaining the adsorption behavior of TTZ on MIL-88 A/NiFeLDH@SA. Thermodynamic studies conducted that the adsorption process is spontaneous and exothermic.
Few-Layer Graphene Coated on Indium Tin Oxide Electrodes Prepared by Chemical Vapor Deposition and Their Enhanced Glucose Electrooxidation Activity
(Wiley, 2019) Caglar, Aykut; Ulas, Berdan; Sahin, Ozlem; Kivrak, Hilal Demir
At present, few-layer graphene is deposited on copper (Cu) foil by chemical vapor deposition (CVD) method. Then, the few-layer graphenes produced on the Cu foil are coated onto the indium tin oxide (ITO) electrode to investigate their glucose electrooxidation activities. Hexane and hydrogen flow rate and deposition time parameters with CVD method are examined on different Cu foils. These electrodes are characterized by scanning electron microscopy-energy dispersive X-ray analysis (SEM-EDX), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. Furthermore, glucose electrooxidation is examined with cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) measurements. One could note that the graphene network is clearly visible from SEM images. The deconvoluted XPS spectrum indicates that carbon appeared in the form of non-oxygenated ring C atoms for few-layer graphene. The few-layer graphene structure is confirmed by Raman analysis. Few-layer graphene/ITO produced at 5 sccm Hexane and 50 sccm hydrogen flow rate and 20minutes deposition time (G7/ITO) reveals the best electrode activity. The specific activity of G7/ITO electrode is obtained as 6.58mAcm(-2). According to CV, CA, and EIS results, G7/ITO electrode has high electrocatalytic activity, stability, and resistance in comparison with other electrodes.
Glucose Electrooxidation Modelling Studies on Carbon Nanotube Supported Pd Catalyst With Response Surface Methodology and Density Functional Theory
(Pergamon-elsevier Science Ltd, 2022) Kaya, Sefika; Ulas, Berdan; Duzenli, Derya; Onal, Isik; Er, Omer Faruk; Yilmaz, Yonca; Kivrak, Hilal
In this study, carbon nanotube supported Pd catalysts (Pd/CNT) are synthesized at different weight percentages by the sodium borohydride (NaBH4) reduction method to investigate catalytic performance of glucose electrooxidation reaction. 0.5% Pd/CNT, 3% Pd/CNT, and 7% Pd/CNT catalysts are characterized by using X-ray diffraction (XRD), electron microscopy with energy dispersive X-ray (SEM-EDX), and N2 adsorption-desorption measurements. The average particle size and surface area of 3% Pd/CNT catalyst are determined as 46.33 nm and 129.48 m2/g, respectively. Characterization results indicate that Pd/CNT catalysts are successfully prepared by NaBH4 reduction method. Cyclic voltammetry measurements are performed to investigate the effect of Pd loading for the glucose electrooxidation. CV results reveal that 3% Pd/CNT catalyst exhibits best glucose electrooxidation activity. Following this, experimental optimization is performed to obtain maximum glucose electrooxidation activity via response surface methodology (RSM). Estimated and experimental specific activities at optimum experimental conditions are assigned as 6.186 and 5.832 mA/cm2, respectively. To understand the glucose electrooxidation activity on the surface of Pd/CNT, surface modeling is also performed with density functional theory (DFT) method to investigate adsorption of glucose molecule on CNT supported Pd surface. The DFT results emphasize that the addition of Pd atom to the CNT structure significantly improves the catalytic performance in glucose electrooxidation.
Highly Active Polyethylene Glycol Grafted Cellulose Supported Pd Nanoparticles for Glucose Electrooxidation
(Elsevier, 2024) Ulas, Berdan; Yilmaz, Yonca; Gok, Ozgul; Kivrak, Hilal
In this study, poly(ethylene glycol) (PEG) grafted cellulose (CE) composite catalyst support material (PEG -CE) was obtained by chemically cross -linking PEG at varying molecular weight and CE with isophorone diisocyanate (IPDI) and 2,4-toluylene diisocyanate (TDI). PEG -CE supported Pd (Pd/PEG-CE) catalyst was prepared by the chemical reduction method. The crystal size of the Pd/PEG-CE catalyst is 4.79 nm and its crystal structure has been determined to be face -centered cubic Pd. Elemental mapping results indicate that Pd was reduced onto PEGCE successfully and uniformly. Pd exists in the elemental and Pd -O form in the catalyst system. The Pd loading rate of Pd/PEG-C_IPDI catalyst was determined as 18.8% by mass. Among the PEG-CEs prepared with TDI and IPDI, PEG4000-CE_TDI and PEG6000-CE_IPDI displayed the highest specific activities of 1.03 and 1.50 mA cm -2 for glucose electrooxidation. With Pd reduction on PEG4000-CE_TDI and PEG6000-CE_IPDI, the specific activities increased to 1.62 mA cm -2 and 6.97 mA cm -2. Pd/PEG6000-CE_IPDI has the highest electrocatalytic activity and stability in this study for glucose electrooxidation and is an encouraging anode catalyst for direct glucose fuel cells.
Highly Active Rupd Bimetallic Catalysts for Sodium Borohydride Electrooxidation and Hydrolysis
(Springer, 2022) Kaya, Sefika; Yilmaz, Yonca; Er, Omer Faruk; Alpaslan, Duygu; Ulas, Berdan; Dudu, Tuba Ersen; Kivrak, Hilal
In the present study, bimetallic RuPd/carbon nanotube (RuPd/CNT) electrocatalysts were synthesized at different molar ratios by sodium borohydride (NaBH4) reduction. These catalysts were characterized with advanced surface characterization techniques such as x-ray diffraction (XRD), scanning electron microscopy with energy dispersive x-ray (SEM-EDX), and x-ray photoelectron spectroscopy (XPS). The activities of these catalysts towards electrooxidation of NaBH4 and hydrogen production from hydrolysis/methanolysis of NaBH4 were investigated. According to XRD results, the particle sizes of Ru/CNT and Ru60Pd40/CNT catalysts were calculated as 3.16 and 3.05 nm, respectively. The distribution and elemental composition of Ru and Pd nanoparticles on CNT were obtained by SEM-EDX analysis. The XPS method was used to determine the oxidation states of Ru and Pd on the CNT surface. The electrochemical activities of these catalysts were determined by cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) measurements. The results show that the Ru60Pd40/CNT catalyst has the highest current mass activity with 2161.94 mA/mg Ru (12.72 mA/cm(2)) current density. Consequently, the RuPd/CNT catalyst is a promising anode catalyst for direct borohydride fuel cells (DBFC) with good stability and high activity.
Highly Efficient Metal Free Aldehyde-Functionalized Indoles for Direct Glucose Fuel Cell Anode Catalyst
(Pergamon-elsevier Science Ltd, 2024) Karatekin, Hatice Calis; Ulas, Berdan; Yilmaz, Yonca; Kivrak, Hilal; Kivrak, Arif
In this study, alternative organic catalysts to metal -containing catalysts for glucose electrooxidation were prepared by the Suzuki Miyaura coupling reaction method and characterized by nuclear magnetic resonance (NMR), fourier transform infrared spectroscopy (FT-IR), and liquid chromatography with tandem mass spectrometry (LCMS -MS). InTA-1, InPA-1, InFA-1, InTA-2, InPA-2, InFA-2, InTA-3, InFA-3, and InPA-3 were obtained with the yield of 74%, 82%, 72%, 70%, 75%, 68%, 60%, 71%, and 85%. Among the synthesized catalysts, the InTA-3 catalyst possesses the highest electrocatalytic activity (3.17 mA cm -2 ) and long-term stability compared to other organic catalysts. InTA-3 catalyst has the lowest charge transfer resistance toward glucose electrooxidation. It was concluded that as a metal -free catalyst, InTA-3 is a cheap and promising electrocatalyst for direct glucose fuel cell anode.