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Öğe Bio-reduced GO/Pd nanocomposite as an efficient and green synthesized catalyst for hydrogen evolution reaction(John Wiley and Sons Ltd, 2021) Balun Kayan, Didem; Turunç, ErsanIn this work, we introduced a green methodology for the production of palladium (Pd) decorated reduced graphene oxide (rGO), using an endemic plant of Onosma malatyana Binzet (OMB) root extract for the first time and used it as an electrocatalyst for hydrogen evolution reaction (HER) in aqueous acidic media. Benefiting from the synergetic effect between rGO and Pd nanoparticles, the as-prepared bio-reduced GO/Pd (bio-rGO/Pd) nanocomposite exhibits a remarkable performance towards HER when the results compared with the bio-rGO and bio-rPd nanocomposite. The HER overpotential at a current density of 10 mA?cm?2 for bio-rGO/Pd was only 0.17?V. The Tafel slope of the bio-rGO/Pd nanocomposite film obtained from the HER polarization curves exhibits 154?mV?dec?1, showing that the process is limited by the Volmer reaction step. In addition, the bio-rGO/Pd nanocomposite electrode also showed an outstanding stability after a long-term potential cycling measurement. It possesses a high synergetic effect, low charge transfer resistance and considerable electrochemical surface area. The all obtained results demonstrated that the bio-rGO/Pd will be a promising green synthesized HER catalyst.Öğe Dinitrogen reduction on a polypyrrole coated Pt electrode under high-pressure conditions: Electrochemical impedance spectroscopy studies(2015) Balun Kayan, Didem; Köleli, FatihThe electrochemical impedance spectroscopy (EIS) responses of a polypyrrole (PPy)-coated platinum electrode were investigated during N2 -reduction to ammonia in aqueous medium. Kinetic parameters such as film resistance, pore resistance, and double layer capacitance were analyzed as a function of applied potential and polymer film thickness. The relation between kinetic parameters was discussed by combining electrolysis results. It was found that the optimum film thickness of polypyrrole was 0.73 µm and optimum potential for ammonia synthesis was –0.150 V under 60 bar N2 -pressure. The impedance responses under these conditions presented the lowest pore resistance value of ca. 2 ? cm2 . The electrolyte resistance was also 2 ? cm2 and the film resistance was ca. 5 ? cm2 . Tafel slopes calculated from the Tafel curve and EIS-Tafel diagram gave corresponding results: 0.121 V dec ?1 and 0.128 V dec ?1 , respectively; ?-transfer coefficient of 0.49 and an exchange current density with a value of 3.17 10 ?3 A cm ?2 were characteristic for Had formation in acidic aqueous medium.Öğe Electrocatalytic hydrogen production on a modified pencil graphite electrode(Pergamon-Elsevier Science Ltd, 2017) Balun Kayan, Didem; Koçak, Derya; İlhan, Merve; Koca, AtıfThe development of Polyaniline (PAni)-Chitosan (Chi) and PAni-Chi/Au conducting composite films coated on pencil graphite and used as electrocatalysts for hydrogen production from water is discussed in this study for the first time. The obtained PAni-Chi composite films and PAni-Chi/Au nanostructured composite films were characterized by scanning electron microscopy (SEM), energy-dispersive spectrometer (EDS) and evaluated as hydrogen evolution reaction (HER) electrocatalysts in an acidic medium. The effect of the film thickness of the PAni-Chi composite film and the effect of the Au electrodeposition on this film were systematically studied by cyclic voltammetry (CV), Tafel polarization curves and electrochemical impedance spectroscopy (EIS). It has been established that the main pathway for the HER is via the Volmer Heyrovsky mechanism with the Volmer reaction being the rate-determining step. This highly active, stable and cost-effective modified pencil graphite electrode is a promising electrocatalyst for hydrogen production from water. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.Öğe Electrocatalytic hydrogen production on GCE/RGO/Au hybrid electrode(Elsevier Ltd, 2018) Balun Kayan, Didem; Koçak, Derya; İlhan, MerveWe have prepared a nanocomposite hybrid film to produce a collaborative network of gold (Au) nanoparticles that are highly dispersed on reduced graphene oxide (RGO) sheets, and tested it for electrocatalytic hydrogen production. The RGO/Au nanocomposite film synthesized on glassy carbon electrode (GCE) allows significant improvements to the electron-transfer process. The Au nanoparticles decorated on the surface of graphene increases the electron density, which synergistically promote the adsorption of hydrogen atoms on the graphene sheets and consequently enhance the hydrogen evolution reaction (HER) activity. The surface properties of the composite was characterized by field-emission scanning electron microscopy (FE-SEM) and the electrocatalytical performances evaluated as-prepared electrocatalyst toward (HER) by linear sweep voltammetry (LSV), Tafel polarization curves and electrochemical impedance spectroscopy (EIS) analyses. The GCE/RGO/Au nanohybrid electrode exhibited good catalytic activity for HER with an onset potential of -0.3 V and a Tafel slope of 136 mV dec-1, achieving a current density of 10 mA cm-2 at an overpotential of -0.43 V. © 2018 Hydrogen Energy Publications LLCÖğe Enhancing the performance of unitized regenerative proton exchange membrane fuel cells through microwave-synthesized chitosan based nanocomposites(Elsevier, 2024) Yelegen, Nebi; Kümük, Berre; Balun Kayan, Didem; Baran, Talat; Kaplan, YükselThe membrane electrode assembly (MEA) is a core component of unitized regenerative proton exchange membrane fuel cells (UR-PEMFCs). The studies aimed to improve the cell performance and reduce the cost of the MEAs for the widespread adoption of UR-PEMFCs. The present study focuses on modifications of MEA. For this purpose, an innovative nanocomposite electrocatalyst was developed by using a carbon-based support material containing platinum nanoparticles with a diameter of approximately 20–30?nm via microwave synthesis technique. The electrocatalyst was developed by a single-step process, consist of multi-walled carbon nanotubes (MWCNT), graphitic carbon nitride (g-C3N4), chitosan (Chi), and platinum nanoparticles (MWCNT/g-C3N4/Chi/Pt nanocomposite). With the development of this support material, a relatively economical and effective electrocatalyst was obtained by large surface area and using the platinum on this surface at the nano level. The prepared catalyst was applied to commercially available membrane electrode assemblies with an active area of 100?cm2. Single-cell and triple-stack performance tests were conducted, and an increase of 17.13?% in the electrolyzer mode and 16.98?% in the fuel cell mode was achieved in single-cell performance with this applied electrocatalyst. Furthermore, an enhancement of 16.96?% in the electrolyzer mode and 16.81?% in the fuel cell mode was discerned in the UR-PEMFC stack. Beside the experimental studies, a numerical model of the modified membrane properties has been developed and validated through experimental data.Öğe Facile fabrication of Sn/SnOx electrode as an efficient electrocatalyst for CO2 reduction to formate(Elsevier Ltd, 2023) Rende, Kumru; Balun Kayan, Didem; Çolakerol Arslan, Leyla; Ergenekon, PınarProducing valuable hydrocarbons via electrochemical reduction of CO2 has been a promising active research area. In this study, it was aimed to develop a low-cost and efficient Sn-based electrode reducing CO2 to formate with high selectivity. SnOx thin-film electrode was prepared via potentiostatic electrodeposition at the potentials of ?0.5 V, ?0.6 V, ?0.7 V, and ?0.8 V vs. Ag/AgCl on a pure Sn plate for 300 s in an acidic media. The Sn/SnOx electrode which was prepared at ?0.6 V was found to have the highest Faradaic efficiency. Electrochemical reduction of CO2 was carried out on this Sn/SnOx electrode in aqueous CO2-saturated 0.1 M KHCO3 solution. The optimum values for the parameters which have significant impacts on Faradaic efficiency for producing formate namely, electrolysis potential and electrolysis time were determined. The maximum Faradaic efficiency of formate on the Sn/SnOx electrode was obtained as 74.7 % at the applied potential of ?1.8 V in an H-type cell. The maximum Faradaic efficiency of formate obtained on the Sn/SnOx electrode reached about twice the value obtained on the Sn plate (39.7 %). The results also indicated that the Sn/SnOx electrode has higher catalytic stability and electrochemically active surface area (2.08 cm2) than the bare Sn plate (0.82 cm2). This study showed that an efficient Sn/SnOx electrode can be developed with a simple method that involves only a SnSO4/H2SO4 solution and as short as 300 s plating duration via electrodeposition at a lower overpotential of ?0.6 V. The novelty of this study can be attributed to the combination of simple and unique electrocatalyst preparation procedure with less energy consumption and chemical/additive use, short deposition time, and relatively low overpotential for developing an efficient Sn/SnOx electrocatalyst ensuring a high Faradaic efficiency for formate production. Thus, producing formate from the conversion of CO2 which is a waste carbon source, was achieved by a quite simple and economic method.Öğe Hydrogen production via water electrolysis on an active electrocatalyst: rGO/Ni nanocomposite(İbrahim Demirtaş, 2023) Balun Kayan, DidemThe development of inexpensive and effective electrocatalyses are all-important for hydrogen production from water electrolysis. In this study, a facile design of a reduced graphene oxide (rGO) based electrocatalyst decorated with nickel nanoparticles is described. The voltammetric results and the hydrogen evolution reaction (HER) kinetics showed that the as-prepared nanocomposite is an effective and stable electrocatalyst for hydrogen production with a small Tafel slope of 152 mVdec-1 and long-term continuous durability (over 24 h) in 0.5 M H2SO4 solution. Also, the enhanced HER activity was confirmed by characterization results with the porous/greater electroactive surface area. The remarkable increase in electrocatalytic activity was due to the surface roughness and the synergetic chemical coupling effects between rGO and Ni nanoparticles.Öğe İletken polimer/metal nanokompozit yapılarının hidrojen üretiminde elektrokatalitik aktivitelerinin incelenmesi(TÜBİTAK, 2016) Balun Kayan, DidemGünümüzün en büyük problemlerinden biri, enerji gereksiniminin karşılanmasında çok büyük oranda fosil yakıtların kullanılmasıdır. Artan enerji ihtiyacının fosil yakıtlardan sağlanması, çevresel problemlere yol açtığı gibi, enerji maliyetinin de artmasına neden olacaktır. Bu problemlerin çözümü ancak sürdürülebilir enerji kaynakları kullanımıyla gerçekleştirilebilecektir. Bu yüzden bol miktarda bulunan hidrojen, temiz ve ideal bir yakıt olarak geleceğin enerji kaynağı olarak düşünülmektedir. Genellikle doğal gazın buhar reformasyonu ile elde edilen hidrojen gazı üretiminin en basit yolu suyun elektrolizidir. Suyun elektrolizi ile hidrojen üretiminde karşılaşılan en büyük problem, elektrokimyasal sistemde oluşan aşırı gerilim nedeniyle maliyet artışıdır. Bu dezavantajın giderilmesi için son yıllarda katalitik etkinlikleri yüksek metaller ile hazırlanan elektrot materyalleri geliştirilerek daha düşük aşırı gerilimli, elektrokimyasal olarak daha aktif elektrotlar elde edilmeye çalışılmaktadır. Kitosan, son yıllarda yaygın kullanılan en önemli doğal polimerlerdendir. Kimyasal olarak inert olması, yüksek mekanik dayanıklılığı, biyolojik olarak parçalanabilmesi, yüksek kaliteli film oluşturabilmesi, diğer materyallerle kompozit oluşturabilmesi ve en önemlisi düşük maliyeti, bu doğal polimerin kullanım alanını arttırmıştır. Diğer taraftan çeşitli iletken polimerlerle modifiye elektrotlar üzerine metal nanopartiküller kontrol edilebilir boyutlarda biriktirilebilmektedirler. Böylelikle katalitik açıdan önemli nanoparçacıkların, kompozit yapıya katalitik aktivite kazandırması amacıyla iletken polimerler destek ortamı olarak kullanılmaktadırlar.Öğe Improvement of anti-corrosion performance (surface and near the cut edge) and mechanical properties of epoxy coatings modified with nano, micro and hybrid ZnO particles(SAGE Publications Ltd, 2023) Kabaoğlu, Emre; Karabörk, Fazliye; Balun Kayan, Didem; Akdemir, AhmetComposites were formed by incorporating nano, micro and hybrid-ZnO particles into the epoxy matrix at the same loading levels (3%) and applied at 90 ?m thickness on the galvanized steel substrate using a film applicator in this study. The improvement in anti-corrosion performance and mechanical and physical properties of the composite coatings were evaluated using various tests and techniques such as salt-spray, electrochemical impedance spectroscopy, nanohardness, microscratch, cross-cut, bending, Fourier transform infrared spectroscopy, thermogravimetric and Scanning electron microscopy. The corrosion performance of the composite coatings near the cut edge is discussed in detail as well as on the surface of galvanized steel. The results show that the addition of all ZnO particles has a positive effect on the corrosion resistance and mechanical properties of the coatings. The addition of nano, micro and hybrid ZnO particles increased the hardness of the composites by 52, 37 and 56%, respectively, compared to the neat epoxy. Although the cathodic protection performance is weakened near the cut edge due to the loss of Zn after thermal cutting, high barrier protection was provided with composite coatings, especially micro ZnO/Epoxy composite coating.Öğe Improvement of electrochemical and structural properties of polycarbazole by simultaneous electrodeposition of chitosan(2017) Balun Kayan, Didem; Polat, VeyselPolycarbazole/chitosan composite materials were synthesized electrochemically at various loadings of chitosan (Chi). Their electrochemical, structural, thermal, and morphological characterizations were investigated by cyclic voltammetry, chronoamperometry, electrochemical impedance spectroscopy, Fourier transform infrared spectroscopy, thermal gravimetry, and scanning electron microscopy. Further electrical conductivity was measured using a four-point probe technique. The electrochemical results showed that the electrical conductivity of the polymeric composite film was increased by increasing the amount of Chi in the electrolyte medium. The as-prepared composite films exhibited enhanced electrical conductivity and structural properties of polycarbazole due to the presence of Chi in the composite films.Öğe Kitosan destekli au nanopartiküller ile modifiye edilmiş alüminyum elektrotta hidrojen gazı üretimi(Çukurova Üniversitesi, 2017) Balun Kayan, Didem; İlhan, Merve; Koçak, DeryaGünümüzün en büyük problemlerinden biri, enerji gereksiniminin karşılanmasında çok büyük oranda fosil yakıtların kullanılmasıdır. Artan enerji ihtiyacının fosil yakıtlardan sağlanması, çevresel problemlere ve enerji maliyetinin artmasına neden olmaktadır. Bu problemlerin çözümü ancak sürdürülebilir enerji kaynakları kullanımıyla gerçekleştirilebilecektir. Bu yüzden bol miktarda bulunan hidrojen, temiz ve ideal bir yakıt olarak geleceğin enerji kaynağı olarak düşünülmektedir. Hidrojen gazı üretiminin en basit yolu suyun elektrolizidir. Suyun elektrolizi ile hidrojen üretiminde karşılaşılan en büyük problem, elektrokimyasal sistemde oluşan aşırı gerilim nedeniyle maliyet artışıdır. Bu çalışmada suyun elektrolizi ile hidrojen elde etmek amacıyla ucuz bir materyal olarak seçilen alüminyum elektrodun yüzeyi, önce polianilin (PAni)-Kitosan kompozit yapısıyla modifiye edilmiş, daha sonra elde edilen bu kompozit yapı üzerine hidrojen oluşumunda yüksek katalitik aktivite gösteren altın (Au) nanopartiküller ayrıştırılmıştır. Elde edilen tüm yapıların yüzey özellikleri incelenmiş ve elektrokimyasal hidrojen üretimindeki katalitik aktiviteleri çeşitli elektrokimyasal yöntemler kullanılarak karşılaştırılmıştır.Öğe Simultaneous electrocatalytic reduction of dinitrogen and carbon dioxide on conducting polymer electrodes(ELSEVIER SCIENCE BV, 2016) Balun Kayan, Didem; Köleli, FatihThe conversion of carbon dioxide with nitrogen containing compounds into valuable materials consistings of C-N bond is a very attractive research area due to today's energy requirements. The simultaneous electrocatalytic reduction of carbon dioxide and dinitrogen was investigated at 60 bar (30 bar N-2+30 bar CO2) in this study. The electrochemical reduction was achieved on polyaniline (PAni) and polypyrrole (PPy) coated platinum electrodes at -0.165V, the lowest possible overpotentials, known in the literature. The main products from the CO2 and N-2 reduction were ammonia, urea and formic acid. The electrochemical reduction performed in an aqueous 0.1 M Li2SO4/0.03 MH+ solution was characterized by using cyclic voltammetry, potentiostatic electrolysis and Tafel diagrams in order to analyze the polymer selectivity as well as its reactivity as a function of the applied potential. Hence, CO2 and N-2 were converted into value added chemicals, which included urea; an important raw material for the chemical industry with high nitrogen content.Öğe The activity of PAni-Chitosan composite film decorated with Pt nanoparticles for electrocatalytic hydrogen generation(Pergamon-Elsevier Science Ltd, 2016) Balun Kayan, Didem; Koçak, Derya; İlhan, MerveTo develop low-cost, highly efficient and stable electrocatalysts is one of the main challenges for hydrogen production from a water electrolysis system. Herein, we describe platinum nanoparticles supported on pencil graphite modified by a Polyaniline-Chitosan composite film that could be used for such a system. This composite electrocatalyst was found to be very active in catalysing hydrogen evolution reactions in acidic medium. The catalytic activity for the hydrogen evolution reaction (HER) was analysed by electrochemical techniques that promoted the kinetics of the reaction following the Volmer-Heyrovsky mechanism. The porous structure of the catalyst provides large current densities for Had formation and hydrogen evolution. Thus, this study implies that the pencil graphite coated with Polyanffine-Chitosan/Pt nanostructured material is a promising electrocatalyst for electrolytic hydrogen production due to its favourable kinetics and that it retains its performance after long-term electrolysis. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.Öğe The role of acidic, alkaline and hydrothermal pretreatment on pyrolysis of wild mustard (Sinapis arvensis) on the properties of bio-oil and bio-char(Elsevier Ltd, 2022) Alayont, Şenol; Balun Kayan, Didem; Durak, Halil; Kulaksız Alayont, Esra; Genel, SalihIn this study, the biomass (Sinapis arvensis) was pretreated with acidic (H2SO4, HCI), alkaline (NaOH, KOH) and high temperature water (HTW) after this samples pyrolyzed at 350, 450 and 550 °C. GC–MS, FT-IR, Elemental, 1H NMR and SEM analysis methods were used in the characterization of the products obtained at the end of the pyrolysis process. It has been determined that alkaline and acidic pretreatment increase the liquid product yield and also support the formation of high energy value biochar. According to the liquid product content obtained as a result of pyrolysis, HTW and alkaline pretreatments are more effective in the formation of mono aromatics, and acidic pretreatments are more effective in the production of aliphatic.
