İletken polimer/metal nanokompozit yapılarının hidrojen üretiminde elektrokatalitik aktivitelerinin incelenmesi

Günümüzün 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.One of the major problems of today’s world is in its heavy dependency on fossil fuels for energy requirements. The increase in energy requirements causes environmental problems and will leads to an increase in energy costs. It has already been obvious that the solution to these problems is to use of sustainable energy resources. Since hydrogen, the most abundant element is the cleanest and ideal fuel, has been considered as the fuel of the future. The hydrogen produces generally by the steam reforming of natural gas but the simplest way of hydrogen production is the electrolysis of water. The major problem in the electrolysis of water for the hydrogen evolution is the increase in costs due to overvoltage of the electrochemical system. Various electrode materials have been trying to develop by using metals which have high catalytic activity to overcome this disadvantage. Chitosan is the one of the most important natural polymer used in recent years. This natural polymer exhibits characteristic properties; such as chemical inertness, high mechanical strength, biodegradability, biocompatibility, high-quality film-forming properties and low cost. On the other hand, metal nanoparticles can be deposited in controllable size on various electrodes which modified by conducting polymers. Thus, in order to provide catalytic activity to the composite, the conducting polymers have been used as supporting medium

Bio-reduced GO/Pd nanocomposite as an efficient and green synthesized catalyst for hydrogen evolution reaction

*Balun Kayan, Didem ( Aksaray, Yazar )In 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

Improvement of electrochemical and structural properties of polycarbazole by simultaneous electrodeposition of chitosan

Balun Kayan, Didem (Aksaray, Yazar)Polycarbazole/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

Dinitrogen reduction on a polypyrrole coated Pt electrode under high-pressure conditions: Electrochemical impedance spectroscopy studies

Balun Kayan, Didem (Aksaray, Yazar)The 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 Ω cm2 . The electrolyte resistance was also 2 Ω cm2 and the film resistance was ca. 5 Ω 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; α-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

Enhanced catalytic activity of ppy-coated pencil electrode in the presence of chitosan and Au nanoparticles for hydrogen evolution reaction

WOS: 000410749000004Catalytically active and low-cost electrocatalysts for the production of hydrogen from water are extremely important for future renewable energy systems. Here, we report the fabrication of a facile pencil graphite electrode modified with polypyrrole-chitosan/Au nanoparticles and tested its performance for electrocatalytic hydrogen evolution reaction (HER) as a model process. The porous surface of the pencil graphite electrode (PGE) was modified potentiostically by polypyrrole (PPy) at various film thicknesses in the presence of chitosan (Chi), which is a natural biopolymer, in the electrolyte medium. After the optimum film thickness had been obtained, the Au particles electrodeposited on to the PPy/Chi composite film at the nano-scale to benefit both from its well-known high catalytic activity and to reduce the amount of precious metal Au to prepare a low-cost eletrocatalyst. The performance of this composite catalyst on the H+ reduction (H-ad formation) and thereby on the hydrogen evolution was investigated. Data from cyclic voltammetry (CV), Tafel polarization curves, and electrochemical impedance spectroscopy (EIS) demonstrated that the current densities related to the electron transfer rate changed with the thickness of the composite film, and the catalytic activity was enhanced more with deposition small amount of Au on to the catalyst surface.Scientific and Technological Research Council of Turkey (TUBITAK) [TBAG-114Z315]; Scientific Research Projects Coordination Unit of Aksaray University [2015-036]; Science and Technological Application and Research Center of Aksaray UniversityThe authors gratefully acknowledge financial support from The Scientific and Technological Research Council of Turkey (TUBITAK) (Project Number TBAG-114Z315), Scientific Research Projects Coordination Unit of Aksaray University (2015-036) and Science and Technological Application and Research Center of Aksaray University

Simultaneous electrocatalytic reduction of dinitrogen and carbon dioxide on conducting polymer electrodes

WOS: 000364256000010The 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.Mersin University Research Foundation [BAP-FBE KB (DBK) 2006-3 DR]; Scientific and Technological Research Council of Turkey [TUBITAK-104T353]The authors gratefully acknowledge the Mersin University Research Foundation (BAP-FBE KB (DBK) 2006-3 DR) and The Scientific and Technological Research Council of Turkey (TUBITAK-104T353) for the financial support

Hydrogen gas production on aluminium electrode modified by chitosan supported with au nanoparticles

Günümüzün 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.One of the major problems of today‟s world is in its heavy dependency on fossil fuels for energy requirements. The increase in energy requirements causes environmental problems and leads to an increase in energy costs. It has already been obvious that the solution to these problems is to use of sustainable energy resources. Since hydrogen, the most abundant element is the cleanest and ideal fuel, has been considered as the fuel of the future. The simplest way of hydrogen production is the electrolysis of water. The major problem in the electrolysis of water for the hydrogen evolution is the increase in costs due to overvoltage of the electrochemical system. In this study, first the surface of the aluminium electrode as a cheap material, coated with polyanilin (PAni)-Chitosan composite film, then the gold (Au) nanoparticles electrodeposited on this composite surface which show high catalytic activity toward hydrogen production. The surface properties of the all obtained structures are investigated and the catalytic activities of the structures are compared with various electrochemical techniques for the electrocatalytic hydrogen production

The activity of PAni-Chitosan composite film decorated with Pt nanoparticles for electrocatalytic hydrogen generation

WOS: 000379274500003To 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.Scientific and Technological Research Council of Turkey (TUBiTAK) [TBAG-114Z315]; Scientific Research Projects Coordination Unit of Aksaray University [2015-036]The authors thank to The Scientific and Technological Research Council of Turkey (TUBiTAK) (Project Number: TBAG-114Z315), Scientific Research Projects Coordination Unit of Aksaray University (2015-036) for funding the research

Functionalized rGO-Pd nanocomposites as high-performance catalysts for hydrogen generation via water electrolysis

Designing an efficient electrocatalyst for hydrogen evolution reaction (HER) is an important research area among the energy-related topics. In our study, the surface of the glassy carbon electrode (GCE) has been modified with reduced graphene oxide/(3-aminopropyl) triethoxysilane/Schiff base (rGO/APTES/Scb) composite structure. Palladium (Pd), which is preferred due to its high catalytic activity in HER process, has been embedded on this composite surface by two different methods. The first nanocomposite was obtained by depositing Pd nanoparticles electrochemically on the rGO/APTES/Scb surface, referred to as rGO/APTES/Scb/Pd Nc1. The other nanocomposite was synthesized by complexing Pd2+ with GO/APTES/Scb and then electrochemically reduced after applied to the electrode surface to obtain rGO/APTES/Scb/Pd Nc2. Conventional characterization techniques have been used to determine the surface structure, morphology and the chemical composition of the as-prepared nanocomposites. The results have shown the different distribution of Pd nanoparticles on both electrodes and that obtained from electrochemical tests for HER were also compatible in themselves. Although both nanocomposites showed high performance and stability, rGO/APTES/Scb/Pd Nc2 exhibited slightly better catalytic activity with an onset potential of -190 mV, a Tafel slope of 129 mV of per decade and achieving a current density of 10 mA cm−2 at an overpotential of -148 mV