Browsing by Author "Kivrak, Hilal"

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3-Acrylamidopropyl Cationic Hydrogel Modified Graphite Electrode and Its Superior Sensitivity To Hydrogen Peroxide
(Taylor & Francis inc, 2019) Caglar, Aykut; Kazici, Hilal Celik; Alpaslan, Duygu; Yilmaz, Yonca; Kivrak, Hilal; Aktas, Nahit
A highly sensitive hydrogen peroxide (H2O2) sensor is fabricated by the synthesized 3-Acrylamidopropyl-trimethylammoniumchloride (p(APTMACl)) hydrogel to covered of pen- graphite (PG) electrodes. (p(APTMACl))-PG electrode is characterized using scanning electron microscopy (SEM), Fourier Transform Infrared (FTIR) spectroscopy, and thermogravimetric analysis (TGA). The electrochemical properties of these sensors are investigated by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). The CV behavior of (p(APTMACl))-PG electrode is investigated in 0.1M PBS (pH 7, 5mm diameter of mold). The developed sensor displays significantly enhanced electrocatalytic activity through the H2O2 detection. Linear response of the sensor to H2O2 were observed in the concentration range from 0 to 130 mu M (R-2 = 0.99) with a detection limit of 1.08x10(-6) M, quantification limit of 3.62x10(-6) M (S/N=3) and sensitivity of 2375 mu A/mMcm(2). In addition, interference studies reveal that (p(APTMACl))-PG electrode is not affected by ascorbic acid (AA), uric acid (UA), and dopamine which are common interfering species. The developed sensor is also successfully applied to detect H2O2 in real commercial samples. This study describes a novel strategy to sensing characteristics to hydrogen peroxide by p(APTMACl)-PG electrode.
Alcohol Electrooxidation Study on Carbon Nanotube Supported Monometallic, Pt, Bi, and Ru Catalysts
(Taylor & Francis inc, 2018) Caglar, Aykut; Aldemir, Adnan; Kivrak, Hilal
In the present study, carbon nanotube supported Pt (Pt/CNT), Bi (Bi/CNT), and Ru (Ru/CNT) catalysts are prepared via NaBH4 reduction method for ethanol (C2H5OH), ethylene glycol (C2H6O2), and methanol (CH3OH) electrooxidation. The physical characterization of these as-prepared catalysts is performed by X-ray diffraction (XRD). Furthermore, electrochemical measurements are conducted via cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), chronoamperometry (CA), and linear sweep voltammetry (LSV). Pt/CNT catalyst exhibits the highest catalytic activity and stability compared to Bi (Bi/CNT) and Ru (Ru/CNT) catalysts. It is observed that the electrocatalytic activity of Pt/CNT catalyst for ethylene glycol (C2H6O2) oxidation is higher than its electrocatalytic activities for ethanol (C2H5OH) and methanol (CH3OH) oxidation. Maximum current density of C2H6O2 of Pt/CNT catalyst is about 4 and 5.7 times lower than C2H5OH and CH3OH. Furthermore, electrochemical impedance spectroscopy (EIS), chronoamperometry (CA), and linear sweep voltammetry (LSV) results are in good agreement with CV results in terms of stability and electrocatalytic activity of Pt/CNT. The Pt/CNT catalyst is believed to be a promising anode catalyst for the alcohol fuel cells.
Atomic Layer Deposition-Sio2 Layers Protected Pdconi Nanoparticles Supported on Tio2 Nanopowders: Exceptionally Stable Nanocatalyst for the Dehydrogenation of Formic Acid
(Elsevier Science Bv, 2017) Caner, Nurdan; Bulut, Ahmet; Yurderi, Mehmet; Ertas, Ilknur Efecan; Kivrak, Hilal; Kaya, Murat; Zahmakiran, Mehmet
TiO2 nanopowders supported trimetallic PdCoNi alloy nanoparticles were simply and reproducibly prepared by wet-impregnation followed by simultaneous reduction method, then to enhance their stability against to sintering and leaching atomic layer deposition (ALD) technique was utilized to grow SiO2 layers amongst these surface bound PdCoNi alloy nanoparticles (PdCoNi/TiO2-ALD-SiO2). These new nanomaterials are characterized by the combination of complimentary techniques and sum of their results exhibited that the formation of ALD-SiO2 layers protected well-dispersed and highly crystalline PdCoNi alloy nanoparticles (ca. 3.52 nm) supported on TiO2 nanopowders. The catalytic performance of the resulting PdCoNi/TiO2-ALD-SiO2 in terms of activity, selectivity and stability was investigated in the dehydrogenation of aqueous formic acid (HCOOH), which has recently been suggested as a promising hydrogen storage material with a 4.4 wt% hydrogen capacity, solution under mild conditions. The results collected from our systematic studies revealed that PdCoNi/TiO2-ALD-SiO2 nanomaterial can act as highly active and selective nanocatalyst in the formic acid dehydrogenation at room temperature by providing an initial turnover frequency (TOF) value of 207 mol H-2/mol metal;: h and >99% of dehydrogenation selectivity at almost complete conversion. More importantly, the catalytic reusability experiments separately carried out with PdCoNi/TiO2-ALD-SiO2 and PdCoNi/TiO2 nanocatalysts in the dehydrogenation of formic acid under more forcing conditions pointed out that PdCoNi/TiO2-ALD-SiO2 nanocatalyst displays unprecedented catalytic stability against to leaching and sintering throughout the reusability experiments it retains almost its inherent activity, selectivity and conversion even at 20th reuse, whereas analogous PdCoNi/TiO2 completely lost its catalytic performance. (C) 2017 Elsevier B.V. All rights reserved.
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.
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.
Bimetallic Ruthenium-Cobalt Catalyst Supported on Carbon Nanotubes: Synthesis, Characterization, and Application in Electrochemical Sensing of Isoleucine
(Wiley, 2025) Arici, Omruye Ozok; Caglar, Aykut; Najri, Bassam A.; Aktas, Nahit; Kivrak, Arif; Kivrak, Hilal
In this work, a bimetallic Ru-Co catalyst based on carbon nanotubes (Ru-Co/CNT) with a Ru to Co ratio of 95:5 is developed. The catalyst, featuring a total metal loading of 3% on the CNTs, is synthesized using the NaBH4 reduction method. Several analytical analyses are used to detect the properties of the Ru-Co/CNT catalyst. X-ray diffraction (XRD) provides information on crystal structures of the catalysts, high-resolution transmission electron microscopy (HR-TEM) reveals particle size and distribution, inductively coupled plasma mass spectrometry (ICP-MS) measures the elemental composition, and X-ray photoelectron spectroscopy (XPS) use to investigate the chemical oxidation states. In addition, thermal techniques including temperature-programmed reduction (TPR), temperature-programmed oxidation (TPO), and temperature-programmed desorption (TPD) are used to recognize the active sites on the catalyst's surface and the acidity. Then, the Ru-Co/CNT catalyst is applied as a sensor for isoleucine amino acid for the first time. It shows high performance with these parameters, sensitivity (0.002 mA cm-2 mm), LOD - limit of detection (0.04 mu m), and LOQ - limit of quantification (0.12 mu m). Moreover, the interferences of common serum blood including (D-glucose, uric acid, ascorbic acid, and L-tryptophan) are studied. The findings indicated that the sensor is applicable to work in complex biological systems.
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] .
Carbon Nanotube Supported Cdm(S, Se)/Cdte Anode Catalysts for Electrooxidation of Glucose in Alkaline Media
(Wiley-v C H verlag Gmbh, 2023) Caglar, Aykut; Kivrak, Hilal; Aktas, Nahit
The sequential sodium borohydride (SBH, NaBH4) reduction method was utilized to prepare the 0.1 % CdSe/CNT, 0.1 % CdS/CNT, 0.1 % (CdS-CNT)/CdTe, and 0.1 % (CdSe-CNT)/CdTe catalysts. The XRD, SEM-EDS, TEM, and XPS analyses were used to characterize the catalysts. The electrochemical measurements were examined by cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) analyses for glucose electrooxidation. The characterization analyses revealed that the desired structure was formed on the support material. The electrochemical analysis results indicated that the 0.1 % (CdSe-CNT)/CdTe catalyst has higher catalytic activity, stability, and resistance compared to other catalysts with a specific activity of 2.4 mA cm(-2).
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.
Catalytic Electro-Oxidation of Hydrazine by Thymol Based-Modified Glassy Carbon Electrode
(Elsevier Sci Ltd, 2022) Sharif, Kawa Hama; Kivrak, Hilal; Ozok-Arici, Omruye; Caglar, Aykut; Kivrak, Arif
In the present, thymol based new organic compounds (4A , 4B and 4C) are designed and synthesized via Steglich Esterification Reactions and Pd-catalyst Sonogashira Coupling Reactions. After isolation and characterization, thymol based hybrid molecules are used for hydrazine (N2H4) electrooxidation reactions as anode catalysts. A variety of metal based anode catalyst have been reported in literature, but this study may be the first study for thymole based hybrid molecules as an anode catalyst in fuel cells. The performance of hybrid molecules was investigated via cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in hydrazine solution. Hybrid 2-isopropyl-5-methylphenyl-4-oxo-4-(5-(p-tolylethynyl)thiophen-2-yl)butanoate (4C) gives the highest performance as 3.66 mAcm(-2) (17.24 mAmg(-1)). Our results displayed that natural products like thymol derivatives may be new generation anode catalyst for fuel cells, and they may be alternative for expensive Pd and Pt based metal anode catalyst.
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] .
The Characterization and Sodium Borohydride Electrooxidation of Novel Carbon Nanotube Supported Copromoted Pd as Anode Catalyst for Fuel Cell
(Wiley, 2022) Caglar, Aykut; Hansu, Tulin A.; Sahin, Omer; Kivrak, Hilal
In the present study, the effect of Co addition on Pd is investigated. Pd/CNT and PdCo/CNT catalysts are prepared via the sodium borohydride (SBH, NaBH4) reduction method. The X-ray diffraction, transmission electron microscope, and inductively coupled plasma-mass spectrometry analyses are performed to characterize the PdCo(70-30)/CNT catalyst. These characterization results reveal that Pd/CNT and PdCo/CNT catalysts are prepared successfully. NaBH4 electrooxidation activities of PdCo/CNT catalysts are examined with electrochemical methods such as cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. PdCo(70-30)/CNT catalyst has 11.52 mA/cm(2) specific activity, 477.18 m(2)/g electrochemical active surface area, and the best electrochemical stability. Pd is a promising catalyst for NaBH4 electrooxidation reaction.
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.
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.
A Comparative Experimental and Density Functional Study of Glucose Adsorption and Electrooxidation on the Au-Graphene and Pt-Graphene Electrodes
(Pergamon-elsevier Science Ltd, 2020) Caglar, Aykut; Duzenli, Derya; Onal, Isik; Tersevin, Ilker; Sahin, Ozlem; Kivrak, Hilal
At present, the graphene is covered on Cu foil with the 5 sccm hexane (C6H14) flow rate, 50 sccm hydrogen (H-2) flow rate, and 20 min deposition time parameters by the CVD method. The graphene on the Cu foil is then covered onto few-layer ITO electrode. Furthermore, the Pt and Au metals are electrodeposited on graphene/ITO electrode with electrochemical method. These electrodes are characterized by Raman spectroscopy and Scanning Electron Microscopy-Energy Dispersive X-Ray analysis (SEM-EDX). The graphene structure is approved via Raman analysis. Au, Pt, and graphene network are openly visible from SEM results. In addition, glucose (C6H12O6) electrooxidation is investigated with cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) measurements. As a result, Pt-graphene/ITO indicates the best C6H12O6 electrooxidation activity with 9.21 mA cm(-2) specific activity (highly above the values reported in the literature). In all electrochemical measurements, Pt-graphene/ITO exhibits best electrocatalytic activity, stability, and resistance compared to the other electrodes. The adsorption of the C6H12O6 molecule is examined theoretically over metal atom (gold and platinum)-doped graphene surfaces using the density functional theory (DFT) method. The interaction between C6H12O6 molecule and OH adsorbed Pt-doped surface is stronger than that of OH adsorbed Au-doped graphene surface thermodynamically according to the reaction energy values. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
A Comparative Study for Sodium Borohydride Dehydrogenation and Electrooxidation on Cerium and Cobalt Catalysts
(Health & Environment Assoc, 2020) Hansu, Tulin Avci; Caglar, Aykut; Sahin, Omer; Kivrak, Hilal
In the present study, Co/CNT and Ce/CNT catalysts are prepared via sodium borohydride (NaBH4) reduction method. Co/CNT and Ce/CNT catalysts are examined to the dehydrogenation and electrooxidation of NaBH4. NaBH4 dehydrogenation activities of these Co/CNT and Ce/CNT catalysts are performed in alkaline environment. 5% Co/CNT catalyst exhibits superior hydrogen evolution compared with other catalysts. Activation energy is calculated using Arrhenius equation. Initial rate for this catalyst is found as 1700 ml H-2 g(cat)(-1) min(-1). As a result of the kinetic calculations, the activation energy of the catalyst is calculated as 44,68775 kj/mol. The degree of reaction (n) is found to be 0.5 by trial and error. In conclusion, 5% Co/CNT catalyst is a promising catalyst for hydrogen production from NaBH4. Cyclic voltammetry (CV) analysis is utilized to examine the electrochemical activity of the catalysts for NaBH4 electrooxidation. 0.1% Co/CNT catalyst has 0.38 mA cm(-2) (3181 mA mg(-1) Co) specific activity.
A Complementary Study on Novel Pdauco Catalysts: Synthesis, Characterization, Direct Formic Acid Fuel Cell Application, and Exergy Analysis
(Pergamon-elsevier Science Ltd, 2018) Kivrak, Hilal; Atbas, Dilan; Alal, Orhan; Cogenli, M. Selim; Bayrakceken, Ayse; Mert, Suha Orcun; Sahin, Ozlem
At present, Pd containing (10-40 wt%) multiwall carbon nanotube (MWCNT) supported Pd monometallic, Pd:Au bimetallic, and PdAuCo trimetallic catalysts are prepared via NaBH4 reduction method to examine their formic acid electrooxidation activities and direct formic acid fuel cell performances (DFAFCs) when used as anode catalysts. These catalysts are characterized by advanced analytical techniques as N-2 adsorption and desorption, XRD, SAXS, SEM-EDX, and TEM. Electronic state of Pd changes by the addition of Au and Co. Moreover, formic acid electrooxidation activities of these catalysts measured by CV indicates that particle size changes in wide range play a major role in the formic acid electrochemical oxidation activity, ascribed the strong structure sensitivity of formic acid electrooxidation reaction. PdAuCo (80:10:10)/MWCNT catalyst displays the most significant current density increase. On the other hand, lower CO stripping peak potential obtained for PdAuCo (80:10:10)/MWCNT catalyst, attributed to the awakening of the Pd-adsorbate bond strength down to its optimum value, which favors higher electrochemical activity. DFAFCs performance tests and exergy analysis reveal that fuel cell performances increase with the addition of Au and Co which can be attributed to synergetic effect. Furthermore, temperature strongly influences the performance of formic acid fuel cell. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
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.
A Comprehensive Study of Hydrogen Production From Ammonia Borane Via Pdcoag/Ac Nanoparticles and Anodic Current in Alkaline Medium: Experimental Design With Response Surface Methodology
(Higher Education Press, 2020) Celik Kazici, Hilal; Yilmaz, Sakir; Sahan, Tekin; Yildiz, Fikret; Er, Omer Faruk; Kivrak, Hilal
In this paper, the optimization of hydrogen (H-2) production by ammonia borane (NH3BH3) over PdCoAg/AC was investigated using the response surface methodology. Besides, the electro-oxidation of NH3BH3 was determined and optimized using the same method to measure its potential use in the direct ammonium boran fuel cells. Moreover, the ternary alloyed catalyst was synthesized using the chemical reduction method. The synergistic effect between Pd, Co and Ag plays an important role in enhancement of NH3BH3 hydrolysis. In addition, the support effect could also efficiently improve the catalytic performance. Furthermore, the effects of NH3BH3 concentration (0.1-50 mmol/5 mL), catalyst amount (1-30 mg) and temperature (20 degrees C-50 degrees C) on the rate of H-2 production and the effects of temperature (20 degrees C-50 degrees C), NH3BH3 concentration (0.05-1 mol/L) and catalyst amount (0.5-5 mu L) on the electro-oxidation reaction of NH3BH3 were investigated using the central composite design experimental design. The implementation of the response surface methodology resulted in the formulation of four models out of which the quadratic model was adjudged to efficiently appropriate the experimental data. A further statistical analysis of the quadratic model demonstrated the significance of the model with a p-value far less than 0.05 for each model and coefficient of determination (R-2) of 0.85 and 0.95 for H-2 production rate and NH3BH3 electrroxidation peak current, respectively.
Dendrimer Templated Synthesis of Carbon Nanotube Supported Pdau Catalyst and Its Application as Hydrogen Peroxide Sensor
(Wiley-v C H verlag Gmbh, 2019) Alal, Orhan; Caglar, Aykut; Kivrak, Hilal; Sahin, Ozlem
At present, CNT supported catalysts were prepared by two different methods as NaBH4 reduction and dendrimer templated NaBH4 reduction method to observe the effect of preparation method on the sensitivity and activity of H2O2 reduction. Then, CNT supported PdxAuy bimetallic nanocatalysts having various atomic ratio were synthesized via novel dendrimer templated NaBH4 reduction method. The resulting materials were characterized employing XRD and TEM. Crystallite size of 10 %Pd0.7Au0.3/CNTdendrimer was obtained from XRD 17.1 nm and mean particle size obtained from TEM is about 15 nm. Moreover, the electrochemical behavior of these catalysts was characterized by cyclic voltammetry (CV) and chronoamperometry (CA) techniques. PdxAuy bimetallic nanocatalysts have excellent electrocatalytic properties and great potential for applications in electrochemical detection. The sensitivity and the limit of detection values for the prepared sensor with monometallic 10 % Pd/CNTdendrimer catalysts are 219.78 mu A mM(-1)cm(-2) and 2.6 mu M, respectively. However, the sensor constructed with 10 %Pd0.7Au0.3/CNTdendrimer modified electrode has a very high sensitivity of 316.89 mu A mM(-1) cm(-2) with a quick response time of 2 s and a wide linear range of 0.001-19.0 mM. In addition, the interference experiment indicated that the 10 % Pd0.7Au0.3/CNTdendrimer nanoparticles have good selectivity toward H2O2.