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  • Küçük Resim
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    Chitosan-based hybrid nanocomposite on aluminium for hydrogen production from water
    (Springer Heidelberg, 2018) Kayan, Didem Balun; İlhan, Merve; Koçak, Derya
    The activity of the hydrogen evolution reaction (HER) has been investigated on a polypyrrole-chitosan composite film decorated with a small amount of gold (Au) nano-particles coated on an aluminium electrode. The facile aluminium modified with such a hybrid nanocomposite and its performance was investigated for hydrogen evolution for the first time. A simple two-step approach was applied, including the first co-electrodeposition of polypyrrole and chitosan at a constant current electrolysis accompanied by the electrodeposition of Au nanoparticles via cyclic voltammetry. The chitosan (Chi), which is available in abundant quantities as a raw material, was incorporated into polypyrrole (PPy) chains, and it plays a key role in keeping metal nanoparticles highly dispersed and interconnected through the formation of a collaborative hybrid network. The low loading (approximate to 2 wt%) of Au on this composite film favoured the related reaction more with a high cathodic current density and reduced the Tafel slope (-152 mV dec(-1)) confirming that the reaction proceeded via the Volmer-Heyrovsky mechanism with a rate control step by the Volmer reaction (proton discharge step). In addition, the long-term durability over 8 h achieved this hybrid composite as a promising nano-electrocatalyst for HER.
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    Enhanced catalytic activity of ppy-coated pencil electrode in the presence of chitosan and Au nanoparticles for hydrogen evolution reaction
    (Springer, 2017) Kayan, Didem Balun; Koçak, Derya
    Catalytically 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.
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    Functionalized rGO-Pd nanocomposites as high-performance catalysts for hydrogen generation via water electrolysis
    (Elsevier Ltd, 2022) Kayan, Didem Balun; Baran, Talat; Menteş, Ayfer
    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.
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    Sn-based chi-rGO/SnO2 Nanocomposite as an Efficient Electrocatalyst for CO2 Reduction to Formate
    (John Wiley and Sons Inc, 2024) Rende, Kumru; Kayan, Didem Balun; Çolakerol Arslan, Leyla; Ergenekon, Pınar
    Designing efficient and cost-effective electrocatalysts in simple ways is very important for energy efficiency. In this sense, nano-sized materials have been extensively utilized for the development of efficient electrodes for electrochemical CO2 reduction. In the present study, we have developed a Sn/chitosan-reduced graphene oxide (chi-rGO)/SnO2 composite electrode via only electrochemical techniques and tested it for electrochemical reduction of CO2 to formate. A bare Sn plate was modified with a reduced graphene oxide layer in the presence of chitosan to get a stable Sn/chi-rGO composite structure and to get more active sites, thus an efficient reduction process was performed. The surface of the Sn/chi-rGO composite was further modified by SnO2 nanoparticles via the potentiostatic electrodeposition method at a fixed applied potential of ?0.6 V for varying periods. The calculated double-layer capacitance (Cdl) of the Sn/chi-rGO/SnO2 electrode was about 80 times larger than the bare Sn plate implying that the coexistence of SnO2 nanoparticles on the (chi-rGO) structure enhanced the electrochemically active sites. The maximum Faradaic efficiency was recorded as 88 % towards the production of formate at an average current density of ?7.36 mAcm?2 at ?1.8 V. Electrochemical measurements and the stability test revealed that the resultant Sn/chi-rGO/SnO2 composite structure behaves as a potential electrode material for efficient CO2 conversion to formate.The study presents a simple and low-cost electrode preparation procedure including only electrochemical techniques which can be conducted within a very short time and without using extra energy and chemicals/additives.