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Öğe 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, HilalIn 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.Öğe A Critical Overview of the State-of-the-Art Methods for Biogas Purification and Utilization Processes(Mdpi, 2021) Atelge, Muhamed Rasit; Senol, Halil; Djaafri, Mohammed; Hansu, Tulin Avci; Krisa, David; Atabani, Abdulaziz; Eskicioglu, CigdemBiogas is one of the most attractive renewable resources due to its ability to convert waste into energy. Biogas is produced during an anaerobic digestion process from different organic waste resources with a combination of mainly CH4 (similar to 50 mol/mol), CO2 (similar to 15 mol/mol), and some trace gasses. The percentage of these trace gases is related to operating conditions and feedstocks. Due to the impurities of the trace gases, raw biogas has to be cleaned before use for many applications. Therefore, the cleaning, upgrading, and utilization of biogas has become an important topic that has been widely studied in recent years. In this review, raw biogas components are investigated in relation to feedstock resources. Then, using recent developments, it describes the cleaning methods that have been used to eliminate unwanted components in biogas. Additionally, the upgrading processes are systematically reviewed according to their technology, recovery range, and state of the art methods in this area, regarding obtaining biomethane from biogas. Furthermore, these upgrading methods have been comprehensively reviewed and compared with each other in terms of electricity consumption and methane losses. This comparison revealed that amine scrubbing is one the most promising methods in terms of methane losses and the energy demand of the system. In the section on biogas utilization, raw biogas and biomethane have been assessed with recently available data from the literature according to their usage areas and methods. It seems that biogas can be used as a biofuel to produce energy via CHP and fuel cells with high efficiency. Moreover, it is able to be utilized in an internal combustion engine which reduces exhaust emissions by using biofuels. Lastly, chemical production such as biomethanol, bioethanol, and higher alcohols are in the development stage for utilization of biogas and are discussed in depth. This review reveals that most biogas utilization approaches are in their early stages. The gaps that require further investigations in the field have been identified and highlighted for future research.Öğe A novel and active ruthenium based supported multiwalled carbon nanotube tungsten nanoalloy catalyst for sodium borohydride hydrolysis(Pergamon-Elsevier Science Ltd, 2023) Hansu, Tulin AvciAt present, a novel and active catalyst, RuW/MWCNT catalyst, was successfully synthe-sized to complete the hydrolysis reaction of sodium borohydride (NaBH4). The activity of Ru catalyst was increased by adding tungsten (W) to ruthenium (Ru) on multi-walled carbon nanotube (MWCNT) support. Surface characterization of the catalyst was performed with scanning electron microscope (SEM-EDX), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmissing electron microscope (TEM) analysis methods. SEM-EDX revealed that RuW (95:5) catalyst metal ratio was obtained at desired nominal ratio. XRD characterization revealed that W addittion to the Ru structure increased its activity by forming an alloy. W addition Ru altered the electronic structure of the Ru. Parameters affecting the hydrolysis performance of RuW/MWCNT catalyst such as temperature, amount of catalyst, NaBH4 concentration and sodium hydroxide (NaOH) concentration were investigated. Adding NaOH to the reaction vessel reduced the activity of the RuW/ MWCNT catalyst. From the hydrolysis measurements, the activation energy of RuW(95-5)/ MWCNT catalyst was found to be 16.327 kjmol-1, the reaction order as 0.61 and the initial rate as 95,841,4 mL H2gcatmin-1. The stability of the RuW/MWCNT catalyst was tested using 5 times and it was observed that this novel RuW/MWCNT catalyst could complete the hydrolysis reaction despite repeated use.(c) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.Öğe A remarkable Mo doped Ru catalyst for hydrogen generation from sodium borohydride: the effect of Mo addition and estimation of kinetic parameters(Springer, 2020) Hansu, Tulin Avci; Sahin, Omer; Caglar, Aykut; Kivrak, HilalAt present, carbon nanotube supported monometallic Ru at 3 wt% Ru loading (3% Ru/CNT) per gram support and bimetallic RuMo at 3 wt% Ru loading per gram support (3% Ru-Mo/CNT) at varying Ru:Mo atomic ratios are synthesized via sodium borohydride (NaBH4) reduction method to investigate their performance towards NaBH4 hydrolysis. These monometallic Ru/CNT and bimetallic Ru:Mo/CNT catalysts prepared at varying Ru:Mo atomic ratios are characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy-energy dispersive X-ray analysis (SEM-EDX), and transmission electron microscopy (TEM). Characterization results reveal that Mo addition to Ru alters the electronic state of the catalysts. The NaOH concentration, the amount of catalyst, the NaBH4 concentration and the temperature parameters that affect the hydrolysis rate of this synthesized and developed catalyst were examined. The kinetic calculations of these parameters related to the order of the reaction were determined. Under optimum conditions catalyst hydrogen production rate was found to be 82,758.43 ml H-2 g(cat)(-1) min(-1). The reaction order (n) and activation energy (E-a) are determined as 0.42 and 35.11 kJ mol(-1). Ru:Mo/CNT catalyst is a novel and promising catalyst for hydrogen generation from NaBH4.Öğe Dual-function macroalgae biochar: Catalyst for hydrogen production and electrocatalyst(Elsevier Sci Ltd, 2024) Bekirogullari, Mesut; Abut, Serdar; Duman, Fatih; Hansu, Tulin AvciIn the current study, Enteromorpha intestinalis, a green macroalgae, has been utilized as a substrate to synthesise a new environmentally friendly and cheap dual -functional (catalyst and electrocatalyst) material. The catalyst was used for efficient hydrogen production from alcoholises sodium borohydride and as an anode catalyst for direct methanol fuel cell applications. At the catalyst synthesis stage, orthogonal arrays of Taguchi is used to find the optimum levels of independent variables for the superior catalyst performance that bears the modest kinetics. The experiments performed in accordance with the L16(45) type orthogonal array. The samples treated at relatively moderate acid, impregnation temperature, impregnation time, burning temperature and burning time showed higher catalytic activities with Exp(5) presenting the optimal catalytic activity followed by Exp(1), Exp (15), Exp(8) and Exp(12), respectively. The experimental levels of coded variables (acid molarity, impregnation temperature and time, burning temperature and time) for Exp(5) were 3 M, 50 C-degrees, 24 h, 500 C-degrees and 2 h., respectively. These finding suggest that providing maximum levels of each of independent variable will not provide high catalytic activity. Taking into account the binary and ternary interactions is an efficient way to determine optimal level of each parameter with regards to maximum hydrogen production rate. The morphological and structural characterization of the optimal catalyst was finally carried out with SEM- EDS, XRD and FT-IR. CV and EIS measurements were taken to determine the electrocatalytic activity of final biochar. Experimental studies revealed that the utilization of E. intestinalis-based electrocatalyst as an anode catalyst for direct fuel cell applications is promising. By employing advanced Taguchi -based experimentation, this research establishes the optimum levels of independent variables, enhancing the catalyst's performance, and highlighting a novel approach to modest kinetics improvement.Öğe Enhanced catalytic performance of Pd/PMAc-g-CNT composite for water splitting and supercapacitor applications(Springer Heidelberg, 2024) Hansu, Tulin Avci; Kaya, Sefika; Caglar, Aykut; Akdemir, Murat; Kivrak, Hilal Demir; Orak, Ceren; Horoz, SabitIn this study, we explore the multifaceted applications of poly(methyl acrylate) (PMAc)-based composites, specifically focusing on their use as an efficient electrocatalyst for water splitting and a high-capacity supercapacitor. After a synthesis step, a characterization study (SEM, TEM, XRD, and Raman spectroscopy) was performed, and based on TEM results, a consistent pattern of small, uniform, and narrowly distributed Pd NPs within the range of 5-10 nm was observed. Also, other analyses confirmed the successful synthesis of PMAc-based composites. Through meticulous experimentation, the electrocatalytic performance of Pd/PMAc-graphene-carbon nanotube (Pd/PMAc-g-CNT) composites was evaluated against that of traditional Pd/PMAc catalysts. Tafel slope analysis was conducted to assess the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) efficiencies, where Pd/PMAc-g-CNT composites demonstrated significantly lower Tafel slopes of 274.53 mV dec(-1) for OER and 389.91 mV dec(-1) for HER. This indicates a superior electrocatalytic activity, enhancing the water splitting process. Furthermore, the same composite showcased an impressive specific capacitance of 132.3 F g(-1) at a current density of 0.5 A/g, markedly surpassing the performance of the Pd/PMAc catalyst. This exceptional capacitance underlines its potential as a high-efficiency energy storage material. The novelty of this research lies in the synergistic integration of PMAc with graphene and carbon nanotubes to fabricate a dual-functional material. This composite not only excels in electrochemical catalysis for energy conversion but also demonstrates remarkable energy storage capabilities. The Pd/PMAc-g-CNT composite, therefore, emerges as a promising candidate for advancing supercapacitor technology and the electrocatalytic efficiency of water splitting, highlighting its dual utility in renewable energy systems.Öğe Exergy and energy analysis of hydrogen production by the degradation of sodium borohydride in the presence of novel Ru based catalyst(Pergamon-Elsevier Science Ltd, 2023) Hansu, Tulin AvciChemically possible hydrogen storage material of the most important and widely used metal hydride compound is sodium borohydride. A current research issue is the devel-opment of systems that allow regulated hydrogen generation employing appropriate cat-alysts for the creation of hydrogen gas from the hydrolysis of sodium borohydride (NaBH4). In this study, controlled hydrogen production from alkali solution of NaBH4 was aimed. On hydrogen generation rate (HGR), the effects of NaBH4 and alkaline solution concentrations, catalyst quantity, and temperature were examined. Considering the energy and exergy analysis, which have gained importance in the international arena in recent years, in this study, the exergy energy analysis of the environment in which the sodium borohydride solution is located was performed. The best one of the Ru-based catalysts synthesized in different atomic ratios was determined as 90:10 RuCr. The surface characterization of the obtained catalyst was carried out using scanning electron microscope (SEM-EDX) and X-ray diffractometer (XRD). In the kinetic calculations, the activation energy was calculated as 35,024 kj/mol and the reaction ordered n was found to be 0,65. By applying exergy and energy analysis to the hydrogen production step, the energy and exergy efficiency of the system were found to be 24% and 7%, respectively.(c) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.Öğe Fabrication of novel palladium-platinum based graphene/ITO electrodes and third metal addition effect through the glucose electrooxidation(Elsevier Science Sa, 2022) Caglar, Aykut; Hansu, Tulin Avci; Sahin, Ozlem; Kivrak, HilalGraphene was coated on Cu foil by chemical vapor deposition (CVD) method. The graphene on the Cu foil was modified by doping N. Then, N-doped graphene (G) was coated on several layers of indium tin oxide (ITO) electrodes. In addition, Pd, Pt, and M (Ag, V, Ni, Zn) metals were electroprecipitated on the graphene/indium tin oxide electrode by electrochemical technique. In this way, the glucose (C6H12O6) electrooxidation activities of these electrodes obtained from PdMPt-N doped graphane/indium tin oxide were investigated by cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) measurements. The obtained materials were characterized by SEM-EDX. Results revealed that the network of Pd, Pt, Ag, V, Ni, Zn and graphene was clearly visible from the SEM results. As a consequence, PdZnPt-N doped G/ITO showed the most effective C6H12O6 electrooxidation activity with a specific activity of 14.5 mA cm(-2), considerably above the literature's published values. In all electrochemical measurements, PdZnPt-N doped G/ITO exhibited the best electrocatalytic activity, stability, and resistance. PdZnPt-N doped G/ITO electrode is promising electrode for glucose electrooxidation.Öğe Hydrolysis and electrooxidation of sodium borohydride on novel CNT supported CoBi fuel cell catalyst(Elsevier Science Sa, 2020) Hansu, Tulin Avci; Caglar, Aykut; Sahin, Omer; Kivrak, HilalAt present, Co, Bi, CoBi, and CoBi/CNT catalysts are prepared via co-precipitation method and sodium borohydride (NaBH4) reduction method for NaBH4 electrooxidation and hydrolysis. These Co, Bi, and CoBi catalysts are characterized by X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), N-2 adsorption-desorption, Inductively Coupled Plasma Mass Spectrometry (ICP-MS), and Temperature Programmed Reduction (TPA). These catalysts are employed for NaBH4 hydrolysis and further measurements are performed to investigate their NaBH4 electrooxidation activity. For NaBH4 hydrolysis, NaOH concentration, reaction temperature, NaBH4 concentration, and catalyst amount are optimized for CoBi and CoBi/CNT catalysts. Furthermore, the rate constants (k) are found between 20 and 50 degrees C and the activation energy is calculated from the Arrhenius equation. The hydrogen generation rates on CoBi (95-5) and % 10 CoBi (95-5)/CNT catalysts are found as 2605.6ml H-2 g(-1)cat min(-1) and 12996 ml H-2 g(-1)cat min(-1), respectively. NaBH4 electrooxidation is investigated with cyclic voltammetry (CV), chronoampemmetry (CA), and electrochemical impedance spectroscopy (EIS) measurements. Maximum mass activities are obtained as 5.86 mA mg(-1) Co for CoBi and 25.7 mA mg(-1) Co for CoBi/CNT catalysts. EIS and CA results are also in a good agreement with CV results in terms of stability and electrocatalytic activity of CoBi/CNT catalyst. The CoBi/CNT catalyst is believed to be a promising anode catalyst for the direct borohydride fuel cell (DBFC).Öğe Investigation of a novel Defatted Spent Coffee Ground (DSCG)-supported Ni catalyst for fuel cell and supercapacitor applications(Elsevier, 2024) Hansu, Tulin Avci; Al-Samaraae, R. R.; Atelge, M. R.; Kaya, Mustafa; Kivrak, Hilal Demir; Bogrekci, Ismail; Yildiz, Yalcin SevkiWith the increase in energy demand, a material that can be used in fuel cell applications has been developed for both energy storage and the use of alternative energy sources to fossil fuels. In this study, a new Defatted Spent Coffee Ground (DSCG)-based electrode material was synthesized for two different application areas. A new electrocatalyst synthesis was carried out by subjecting DSCG to chemical activation and carbonization processes. The glycerol electrooxidation performances of the catalysts synthesized at 10-50 % Ni loading rates were investigated by CV measurements. 30 % Ni-DSCG catalyst exhibited the highest catalytic activity with 3.290 mA/ cm2.As 2 .As a result of the electrochemical measurements, 30 % Ni-DSCG catalyst with the best catalytic performance was used as the supercapacitor electrode material. The electrochemical performances of the produced super- capacitor electrodes were tested at room temperature using galvanostatic charge-discharge (GCD), Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques, and the capacity and stability of the electrodes were calculated as a result of the findings. In the calculations, the energy and power density of the 30 % Ni-DSCG supercapacitor electrode were calculated as 22.897 Wh kg(- 1) , 841.114 W kg(- 1) , respectively. The supercapacitor electrode capacitance was found to be 50.48 F/g. Its cyclic capacity was found to be 90 %. It showed that the DSCG-based synthesized electrocatalyst could be a good option for energy storage technology as EDLC electrode material and fuel cell applications as anode catalyst due to its good conductivity, superior cyclic stability, environmental friendliness and low cost.Öğe Investigation of electrochemical properties of tri- and tetravalent boronate ester compounds for supercapacitor applications(Springer Heidelberg, 2022) Akdemir, Murat; Hansu, Tulin Avci; Kilic, Ahmet; Beyazsakal, Levent; Kaya, Mustafa; Horoz, SabitThe motivation of the current study is to use the synthesized tri- and tetravalent boronate esters (C15H16BNO3 center dot HCl(B-1) and C40H42B2Cl2N4O4, (B-2)), respectively, for the first time as electrodes in the presence of different electrolyte solutions in supercapacitor applications and to measure their specific capacitances. As a result of the electrochemical measurements, it is determined by experimental observations that the specific capacitance value of the tetravalent (B-2) electrode is higher than that of trivalent (B-1) in the presence of both different electrolyte solutions. Furthermore, when the morphological properties of both materials are examined, it is observed that tetravalent boronate ester (B-2) has a more porous structure and its surface area is higher than trivalent boronate ester (B-1) as a conclusion of the surface area measurement. As a consequence of this research, it has been demonstrated that tetravalent boronate ester (B-2) can be employed as a promising material for future supercapacitor energy storage applications.Öğe Lake sediment based catalyst for hydrogen generation via methanolysis of sodium borohydride: an optimization study with artificial neural network modelling(Springer, 2021) Bekirogullari, Mesut; Abut, Serdar; Duman, Fatih; Hansu, Tulin AvciIn the current study, lake sediment, a heterogeneous and complex organic matter, utilized as a catalyst upon acid treatment for efficient hydrogen generation from sodium borohydride. In order to synthesise the catalyst that bears the best catalytic activity, ANOVA, cubic stepwise linear regression and artificial neural network optimization techniques were applied to determine the optimal level of treatment parameters. The results suggest that only Taguchi orthogonal arrays method was able to accurately reflect the overall surface of objective variable. Among the 16 catalyst samples Exp(15) showed the superior catalytic activity followed by Exp(13), Exp(12), Exp(14) and Exp(7). The minimum reaction completion time for Exp(15) corresponding to maximum hydrogen production rate of 3247.15 mL/min/gcat was 2.25 min. A detailed characterization of the final product was carried out by using a Fourier transform infrared spectra (FTIR-Perkin Elmer), an X-ray diffractometer (Bruker D8 Advance XRD), a scanning electron microscopy and energy dispersive X-ray spectroscopy. [GRAPHICS] .Öğe Metal-free catalysts for hydrogen production(Elsevier, 2022) Caglar, Aykut; Hansu, Tulin Avci; Demir-Kivrak, HilalCatalysts are vital for speeding up the reaction during hydrogen production. Both metal-based and metal-free catalysts are used. Metal-free catalysts are less expensive than metal-based catalysts and do not have the disadvantages of oxidation and poisoning. Metal-free catalysts doped with heteroatoms, carbon materials, and polymers have been investigated for their high catalytic activity in hydrogen production. Carbon materials are typically high-surface-area carbon forms such as activated carbon, carbon nanotubes, fullerene, graphite, and graphene. In addition, heteroatoms are obtained by adding atoms to carbon materials, such as replacing carbon atoms with heteroatoms such as N, P, or B or bonding heteroatoms such as S, CI, Br, or O to the carbon surface. Hydrogen is produced from boron-based chemical hybrids, water, and other sources. Sodium borohydride (NaBH4), ammonium borane (NH3BH3), and hydrazine borane (N2H4BH3) are boron-based hybrid chemical sources. Examining the different production methods of these hydrogen sources is important for achieving cheaper and more efficient hydrogen production. Water splitting is examined in three categories: electrolysis, thermolysis, and photoelectrolysis. Furthermore, catalyst characterization is a technique that must be studied to relate catalytic activities with their properties. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, and thermogravimetric and differential thermal analysis techniques are examined to determine the composition and structure of metal-free catalyst surfaces. © 2022 Elsevier Inc. All rights reserved.Öğe Ruthenium modified defatted spent coffee catalysts for supercapacitor and methanolysis application(Wiley, 2021) Akdemir, Murat; Hansu, Tulin Avci; Caglar, Aykut; Kaya, Mustafa; Kivrak, Hilal DemirCurrently, a novel green material, defatted spent coffee ground (DSCG), is employed as a support to prepare DSCG supported Ru (DSCG-Ru) material. DSCG and DSCG-Ru materials are characterized by advanced surface analytical techniques such as N-2 adsorption-desorption, X-ray diffraction, X-ray photoelectron spectroscopy, and H-2-temperature-programmed reduction. Characterization results revealed that DSCG-Ru was prepared successfully. First, DSCG-Ru is prepared at varying Ru contents on deoiled coffee waste and hydrogen production experiments are performed by the methanolysis of sodium borohydride on the DSCG-Ru catalysts. It is observed that optimum conditions for the catalyst preparation are examined on the 10% Ru containing DSCG-Ru catalysts and found as 10% Ru, 300 degrees C, and 60 minutes. DSCG catalyst containing 10% Ru completed the methanolysis reaction in 1.5 minutes. Capacitive measurements to investigate the supercapacitor property of DSCG-Ru catalysts prepared at optimum conditions 10% Ru, 300 degrees C, and 60 minutes is investigated by cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge-discharge measurements. Results revealed that gravimetric capacitance of the electrode at a current density is found as of 0.5 A/g and 43 F/g, greater than the literature values. DSCG-Ru, green novel supported Ru catalyst, has a dual promising performance in hydrogen production and supercapacitor measurements.Öğe The preparation and characterization of the novel mono-/binuclear boron-based materials for supercapacitor electrode applications(Springer Int Publ Ag, 2022) Hansu, Tulin Avci; Kilic, Ahmet; Soylemez, Rahime; Akdemir, Murat; Kaya, Mustafa; Horoz, SabitThe goal of this research is to employ synthesized mono- and binuclear boron-containing compounds (C16H12BF6NO2 center dot HCl (B) and C42H34B2Cl2F12N4O4 (B <- N)) as electrodes in supercapacitor applications for the first time and test their specific capacitances in the presence of various electrolyte solutions. Experimental findings show that the specific capacitance value of the binuclear boron-based (B <- N) electrode is larger than that of the mononuclear boron-based (B) electrode in the presence of both distinct electrolyte solutions as a consequence of the electrochemical tests. Moreover, when the morphological qualities of both substances are evaluated, it is discovered that binuclear boron-based (B <- N) has a more porous structure and, as a result of the surface area measurement, has a greater surface area than mononuclear boron-based (B). As a part of this experiment, it has been established that binuclear boron-based (B <- N) is a viable material for future supercapacitor energy storage applications.
