Browsing by Author "Kaya, Sefika"

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Benzotiyofen@pd as an Efficient and Stable Catalyst for the Electrocatalytic Oxidation of Hydrazine
(Elsevier Sci Ltd, 2022) Kaya, Sefika; Ozok-Arici, Omruye; Kivrak, Arif; Caglar, Aykut; Kivrak, Hilal
An efficient methods for the synthesis of 2-(2,5-dimethylphenyl)-3-iodobenzo[b]thiophene (4) is described, and investigated its anode catalyst performance by using electrochemical methods (CV, CA and EIS). When 2-(2,5dimethylphenyl)-3-iodobenzo[b]thiophene (4) is applied, the specific activity is found as 25.811 mA/cm(2). Interestingly, when Palladium (Pd) is electrochemically deposited on the benzothiophene derivative, the catalytic activity increased the 80.930 mA/cm(2). This result is highest than the current metal based anode catalyst. Moreover, EIS and CA measurements display that Pd doped benzothiophene organic catalyst have high stability, and give the low charge transfer resistance. Energy dispersive X-ray (SEM-EDX), electron microscopy, TEM are used for the determination of its surface morphology. As a result, 2-(2,5-dimethylphenyl)-3-iodobenzo[b]thiophene (4) may be alternative electro-catalysts in fuel cell applications.
Carbon Nanotube Supported Ga@pdagco Anode Catalysts for Hydrazine Electrooxidation in Alkaline Media
(Elsevier Sci Ltd, 2022) Kaya, Sefika; Caglar, Aykut; Kivrak, Hilal
In this study, carbon nanotube supported (CNT) monometallic (Pd), trimetallic (PdAgCo), and multimetallic (Ga@PdAgCo) catalysts in different weight percentages (0.5-10%) are synthesized by the NaBH4 reduction method and characterized transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma-mass spectrometry (ICP-MS), and X-ray diffraction (XRD) analytical methods. Ac-cording to the TEM analysis results, while agglomeration doesn't observe for 3% Ga@PdAgCo(80:10:10)/CNT catalyst, agglomeration is observed in certain parts for 7% Ga@PdAgCo(80:10:10)/CNT catalyst. The occurrence of agglomeration has a negative effect on catalytic activity. XRD analysis shows that as metal was added, the diffraction peaks are negatively shifted, thereby forming an alloy. Electrochemical measurements such as cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) are used for the hydrazine electrooxidation activities of the catalysts. The highest specific activity is achieved as 250.39 mA/cm(2) (22592.66 mA/mg Pd) with catalyst. The electrochemical surface area (ECSA) of 3% Ga@PdAgCo/CNT catalysts is also calculated as 1392.43 m(2)/g. The homogeneous distribution of the metals on the support material and the alloy formation has an effect on the catalytic activity for the 3% Ga@PdAgCo(80:10:10)/CNT catalyst. Although Pd is an active metal on its own, the synergistic effect between them as a result of the formation of alloys with different metals and the electronic state change on the catalyst by adding different metals to Pd has a great influence on the catalytic activity. As a result, Ga@PdAgCo/CNT catalyst with its high current value stands out as a new anode catalyst for hydrazine electrooxidation.
Characterization and Electrooxidation Activity of Ternary Metal Catalysts Containing Au, Ga, and Ir for Enhanced Direct Borohydride Fuel Cells
(Springer, 2023) Caglar, Aykut; Kaya, Sefika; Kivrak, Hilal
Carbon nanotube (CNT)-supported catalysts were synthesized by the sodium borohydride (NaBH4) reduction method and characterized by X-ray diffraction, transmission electron microscopy, inductively coupled plasma-mass spectrometry, and X-ray photoelectron spectroscopy analyses. The catalytic activities of the catalysts were examined by cyclic voltammetry, chronoamperometry, electrochemical impedance spectroscopy, and linear sweep voltammetry electrochemical analyses for direct borohydride fuel cells (DBFCs) in NaBH4 solution. The characterization analyses revealed the structure, particle size, and metal ratios of CNT-supported metals. The NaBH4 electrooxidation results indicate that the 3% AuGaIr/CNT catalyst had a specific activity of 5.65 (1529.98 mA mg(-1) Au) mA cm(-2) and higher catalytic activity than the other catalysts. Furthermore, the electrochemical surface area (ECSA) values were obtained by calculating the reduction peak of the metal oxide in the NaOH solution by CV analysis. The ECSA value (128.57 m(2) g(-1)) of 3% AuGaIr/CNT catalyst was much higher than the other catalysts. The 3% AuGaIr/CNT catalyst had faster electron transfer rate with low (961.8 omega) charge transfer resistance (R-ct) and also high stability compared to the other catalysts. The study presents an up-and-coming new type of anode catalyst for DBFC applications. [GRAPHICS] .
Cnt-Supported Multi-Metallic (Ga@pdagco) Anode Catalysts: Synthesis, Characterization, and Glucose Electrooxidation Application
(Springer, 2023) Kaya, Sefika; Caglar, Aykut; Kivrak, Hilal
Here, Ga@PdAgCo catalysts were prepared by sequential reduction using carbon nanotubes (CNT) as support material. The catalysts at different weight percentages were characterized by inductively coupled plasma-mass spectrometry (ICP-MS), transmission electron microscopy (TEM), x-ray photoelectron spectroscopy (XPS), and x-ray diffraction (XRD) analytical techniques. Chronoamperometry (CA), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) measurements were applied to examine the glucose electrooxidation performance of the catalysts. Among the catalysts, the 7% Ga@PdAgCo(CNT) multi-metallic catalyst provided the best mass activity and specific activity of 231.08 mA/mg Pd and 2.475 mA/cm(2), respectively. EIS results revealed that the 7% Ga@PdAgCo(CNT) catalyst has a faster electron transfer rate with low (632 omega) charge transfer resistance (Rct). Consequently, the 7% Ga@PdAgCo(CNT) catalyst stands out as a potential anode catalyst for direct glucose fuel cells.
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.
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]
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.
Glucose Electrooxidation Study on 3-iodo-2-(aryl/Alkyl)benzo[b]thiophene Organic Catalyst
(Springer, 2022) Ozok-Arici, Omruye; Kaya, Sefika; Caglar, Aykut; Kivrak, Hilal; Kivrak, Arif
The compound 3-iodo-2-(aryl/alkyl)benzo[b]thiophene (4A-F) has been synthesized as an anode catalyst using the Sonogashira coupling reaction and the electrophilic cyclization reaction in moderate to excellent yields. The glucose electro-oxidation performance of these catalysts has been investigated by electrochemical methods, such as cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) in 1 M KOH + 1 M C6H12O6 solution. When Pd metal is electrochemically deposited on the organic catalyst to increase the electrocatalytic activities, the Pd@4A catalyst exhibits the highest catalytic activity with 0.527 mA/cm(2) current density than the 4A. The CA and EIS results prove that the Pd@4A catalyst has long-term stability and low charge transfer resistance and may be used in metal-organic catalyst systems as an anode catalyst to improve their performance. The results confirm that benzothiophene-based metal systems will be environmentally friendly materials in 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.
Novel Ti3c2x2 Mxene Supported Bamno3 Nanoparticles as Hydrazine Electrooxidation Catalysts
(Pergamon-elsevier Science Ltd, 2024) Ulas, Berdan; Cetin, Tayfun; Kaya, Sefika; Akinay, Yuksel; Kivrak, Hilal
In this study, MXene Ti3C2X2 and BaMnO3 nanoparticle-doped MXene particles were prepared by HF etching mechanism and hydrothermal method. Scanning electron microscopy-energy dispersive X-ray analysis (SEMEDX), transmission electron microscopy (TEM), and X-ray diffraction (XRD) methods were utilized for the characterization of as-synthesized catalysts. The presence of BaMnO3 nanoparticles in the catalyst system was confirmed by XRD and EDX spectra. The catalytic activity of the BaMnO3/MXene catalyst for hydrazine electrooxidation was investigated by cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) in a basic medium. The mass activities of bare MXene and BaMnO3/MXene for hydrazine electrooxidation were determined as 309.5 and 731.7 mA mg -1, respectively. Increasing specific activity attributed to the improvement of the kinetics for the hydrazine electrooxidation reaction on MXene with the addition of BaMnO3. BaMnO3/MXene has been found to have lower charge transfer resistance and higher electrocatalytic activity than MXene. Novel BaMnO3/MXene catalyst showed super performance for hydrazine electrooxidation.
Optimization of Electrode Preperation Conditions for Enhanced Glucose Electrooxidation on Pt/Cnt by Response Surface Methodology
(Springer, 2022) Kaya, Sefika; Ulas, Berdan; Er, Omer Faruk; Kivrak, Hilal; Yilmaz, Yonca
In this study, glucose electrooxidation activities of carbon nanotube (CNT)-supported Pt catalysts synthesized at various weight percentages and optimum electrode preparation conditions are investigated. For glucose electrooxidation on Pt/CNT, electrode preparation parameters such as amount of catalyst ink (V-c), ultrasonication duration of the catalyst ink (d(u)), and drying duration of the electrode (d(d)) were optimized to obtain maximum specific activity. The catalysts (Pt/CNT) are characterized via N-2 adsorption-desorption, X-ray diffraction, and electron microscopy with energy dispersive X-ray advanced surface analysis techniques. Specific activity for glucose electrooxidation catalyst performance are determined by using cyclic voltammetry (CV) and chronoamperometry (CA) measurements. According to CV measurements, the best electrocatalytic activity obtained is 3.4352 mA/cm(2) with 7% Pt/CNT catalyst. Experimental conditions are optimized via response surface methodology (RSM) for maximizing glucose electrooxidation activity. The predicted specific activity and the actual specific activity are determined to be 5.931 mA/cm(2) and 5.421 mA/cm(2) under optimum conditions such as 7.36 mu L (V-c), 49.54 min (d(d)), and 2.45 min (d(u)).
A Remarkable Synergic Effect of Poly (Acryclic Acid) Hydrogel Anchored Pd Catalysts in Formic Acid Electrooxidation Reaction
(Health & Environment Assoc, 2022) Khalid, Sarwar; Kivrak, Hilal; Alpaslan, Duygu; Kaya, Sefika; Aktas, Nahit
Polymer-based catalysts have never been used before as anode catalysts in direct formic acid fuel cells. At present, Poly (acrylic acid), Poly (AA) was prepared and electrodes were constructed on graphite pencil (G) from these hydrogels. Furthermore, Pd doped Poly (AA)/G electrodes were prepared by employing electrodeposition techniques, and their formic acid electrooxidation (FAEO) activities were examined via cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. These electrodes were characterized by DT-TGA, FTIR, and SEM-EDX. It was observed that Poly (AA)/G were prepared successfully. Poly (AA)/G electrode exhibited promising electrocatalytic activity as a DFAFC anode catalyst. By the modification with Pd, the FAEO activity increased for Poly (AA)/G with 38 mA/cm(2) current density, greater than literature values. In conclusion, it is clear that these Pd doped Poly (AA)/G electrodes have superior activity towards formic acid electrooxidation.