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Öğe Biofunctionalized conductive polymers enable efficient CO2 electroreduction(AMER ASSOC ADVANCEMENT SCIENCE, 2017) Coskun, Halime; Aljabour, Abdalaziz; De Luna, Phil; Farka, Dominik; Greunz, Theresia; Stifter, David; Kus, MahmutSelective electrocatalysts are urgently needed for carbon dioxide (CO2) reduction to replace fossil fuels with renewable fuels, thereby closing the carbon cycle. To date, noble metals have achieved the best performance in energy yield and faradaic efficiency and have recently reached impressive electrical-to-chemical power conversion efficiencies. However, the scarcity of preciousmetalsmakes the search for scalable, metal-free, CO2 reduction reaction (CO2RR) catalysts all themore important. We report an all-organic, that is, metal-free, electrocatalyst that achieves impressive performance comparable to that of best-in-class Ag electrocatalysts. We hypothesized that polydopamine-a conjugated polymer whose structure incorporates hydrogen-bonded motifs found in enzymes-could offer the combination of efficient electrical conduction, together with rendered active catalytic sites, and potentially thereby enable CO2RR. Only by developing a vapor-phase polymerization of polydopamine were we able to combine the needed excellent conductivity with thin film-based processing. We achieve catalytic performance with geometric current densities of 18 mA cm(-2) at 0.21 V overpotential (-0.86 V versus normal hydrogen electrode) for the electrosynthesis of C-1 species (carbon monoxide and formate) with continuous 16-hour operation at >80% faradaic efficiency. Our catalyst exhibits lower overpotentials than state-of-the-art formate-selective metal electrocatalysts (for example, 0.5 V for Ag at 18mA cm(-1)). The results confirm the value of exploiting hydrogen-bonded sequences as effective catalytic centers for renewable and cost-efficient industrial CO2RR applications.Öğe Colloidal CuZnSnSe4-xSx nanocrystals for hybrid solar cells(ELSEVIER, 2015) Kuş, Mahmut; Özel, Faruk; Büyükçelebi, Sümeyra; Aljabour, Abdalaziz; Erdoğan, Ayşenur; Ersöz, Mustafa; Sarıçiftçi, Niyazi SerdarWe report the synthesis of different colloidal CZTSe(4-x)S(x) nanocrystals and their performance in [6,6]-phenyl C61 butyric acid methyl ester (PCBM) based organic/inorganic hybrid bulk heterojunction solar cells. Synthesis of colloidal CuZnSnSe4-xSx were performed and characterized by XRD, TEM, SEM, UV-Visible absorption techniques. Electrochemical and photovoltaic properties were investigated. The best device concept, ITO/PEDOT:PSS/CZTS:PCBM blend (1:10)/Al, showed 280 mu A/cm(2) short circuit current, I-sc with 300 mV open circuit voltage V-oc, and fill factor FF of 0.38. (C) 2014 Elsevier B.V. All rights reserved.Öğe Earth-Abundant Cu2CoSnS4 Nanofibers for Highly Efficient H-2 Evolution at Soft Interfaces(WILEY-V C H VERLAG GMBH, 2015) Ozel, Faruk; Yar, Adem; Aslan, Emre; Arkan, Emre; Aljabour, Abdalaziz; Can, Mustafa; Patir, Imren HatayCu2CoSnS4 (CCTS) nanofibers have been fabricated by electrospinning and exhibit an excellent morphology with an average nanofiber diameter of 150 nm. Polyacrylonitrile (PAN) was used as templating polymer that leads to a decrease in imperfections in the crystalline nanofibers. CCTS and Cu2ZnSnS4 (CZTS) nanofibers, based on abundant and environmental friendly elements, efficiently enhanced the rates of biphasic proton reduction in the presence of an organic solubilized electron donor, decamethylferrocene (DMFc). This work paves the way for the exploration of copper-based chalcogenides as electrocatalysts for the hydrogen evolution reaction to replace noble metal Pt.Öğe Effect of doping on thin film solar cell efficiency based on ZnMn2O4 nanocrystals(ELSEVIER, 2019) Sarılmaz, Adem; Özel, Faruk; Aljabour, Abdalaziz; Khaskheli, Abdul Rauf; Kuş, MahmutThe present study reports, for the first time, a facile synthesis for ternary ZnMn2O4 nanocrystals synthesized by a simple and low cost two-phase method. Those nanocrystals were used on thin film solar cell as active absorber layer. The resulting nanocrystals were characterized by XRD, TEM, AFM-MFM, FTIR and JV characterization techniques to investigate the crystalline behavior, chemical composition, morphology and optical properties. Two phase method allows the successful synthesis of oleic acid (OA) capped ZnMn2O4 nanocrystals with 5-10 nm particle size. After doping of the ZnMn2O4 nanocrystals at different ratios with P3HT:PCBM, an enhancement was observed in the solar cell performances based on thin films. The power conversion efficiency of P3HT:PCBM-ZnMn2O4 thin film solar cell was investigated by J-V characteristic curve and as a result of this study, the highest efficiency was achieved as 3.27% with a doping ratio of 1%. Thus we believe that this work will open a new perspective to the synthesis of ZnMn2O4 materials for applications in the field of energy conversion systems. (C) 2019 Elsevier Ltd. All rights reserved.Öğe Electrospinning of Cu2ZnSnSe4-xSx nanofibers by using PAN as template(ELSEVIER SCIENCE BV, 2015) Ozel, Faruk; Kus, Mahmut; Yar, Adem; Arkan, Emre; Yigit, M. Zeliha; Aljabour, Abdalaziz; Buyukcelebi, SumeyraWe firstly demonstrate the synthesis of Cu2ZnSnSe4-xSx (CZTSeS) nanofibers through versatile electrospinning technique. Polyacrylonitrile (PAN) was used as templating polymer that leads to decrease in imperfections on crystal fibers and yields outstanding structure including a few defects with diameter around 250 nm. Sulfurization and/or selenization processes were carried out separately and simultaneously depending upon the demanded chemical structure. Detailed characterization and electrochemical response indicate their potential application for solar cells as p-type semiconductors. (C) 2014 Elsevier B.V. All rights reserved.Öğe Fabrication of quaternary Cu2FeSnS4 (CFTS) nanocrystalline fibers through electrospinning technique(SPRINGER, 2015) Ozel, Faruk; Kus, Mahmut; Yar, Adem; Arkan, Emre; Can, Mustafa; Aljabour, Abdalaziz; Varal, Nurhan MehmetCopper-based quaternary chalcogenide Cu2FeSnS4 (CFTS) is an important material due to its indium-free nature and presence of earth-abundant elements. Herein, CFTS nanofibers have been first fabricated via a facile two-step approach using a simple and inexpensive electrospinning technique. X-ray diffraction and scanning electron microscopy techniques were used to determine structural, morphological, and compositional features of the obtained films. Nanofibers annealed at 500 degrees C for 1 h were characterized by (112), (200), (220), (312) preferred orientations via X-ray diffraction method. Nanofibers showed well crystallization and tetragonal phase. The average diameters of obtained fibers were found to be 100 +/- 50 nm. Cyclic voltammograms showed that CFTS fibers showed p-type behavior.Öğe A green approach for the production of biodiesel from fatty acids of corn deodorizer distillate(ROYAL SOC CHEMISTRY, 2014) Naz, Saba; Kara, Huseyin; Sherazi, Syed Tufail Hussain; Aljabour, Abdalaziz; Talpur, Farah NazA novel alginic acid derived tin catalyst, tin alginate (Sn-Alg), was successfully synthesized, characterized and applied for methyl esterification. Initially, the amount of catalyst, methanol to fatty acid ratio and reaction time were optimized using an oleic acid standard for esterification. The optimal reaction conditions were found to be 4% catalyst, 1 : 12 oleic acid to methanol mole ratio and 2 h reaction time with 98.7% fatty acid methyl ester recovery. The capability of Sn-Alg beads to esterify the fatty acids of corn deodorizer distillate was evaluated. High recovery (97.6%) of esters was obtained after 8 cycles using reprocessed catalyst under the optimized parameters. The results of the present study indicated that based on the environmental pollution, reusability, avoiding the use of potassium or sodium hydroxides or sulphuric or phosphoric acids, and ease of catalyst separation, the solid Sn-Alg catalyst has a great potential for biodiesel production from highly free fatty acid deodorizer distillates.Öğe Improvement of Catalytic Activity by Nanofibrous CuInS2 for Electrochemical CO2 Reduction(AMER CHEMICAL SOC, 2016) Aljabour, Abdalaziz; Apaydın, Doğukan Hazar; Coşkun, Halime; Özel, Faruk; Ersöz, Mustafa; Stadler, Philipp; Sarıçiftci, Niyazi SerdarThe current study reports the application of chalcopyrite semiconductor CuInS2 (CIS) nanofibers for the reduction of CO2 to CO with a remarkable Faradaic efficiency of 77 +/- 4%. Initially the synthesis of CuInS2 nanofibers was carried out by adaptable electrospinning technique. To reduce the imperfection in the crystalline fiber, polyacrylonitrile (PAN) was selected as template polymer. Afterward, the desired chemical structure of nanofibers was achieved through sulfurization process. Making continuous CuInS2 nanofibers on the cathode surface by the electrospinning method brings the advantages of being economical, environmentally safe, and versatile. The obtained nanofibers of well investigated size and diameter according to the SEM (scanning electron microscope) were used in electrochemical studies. An improvement of Faradaic efficiency was achieved with the catalytic active CuInS2 in nanofibrous structure as compared to the solution processed CuInS2. This underlines the important effect of the electrode fabrication on the catalytic performance. Being less contaminated as compared to solution processing, and having a well-defined composition and increased catalytically active area, the CuInS2 nanofiber electrodes prepared by the electrospinning technique show a 4 times higher Faradaic efficiency. Furthermore, in this study, attention was paid to the stability of the CuInS2 nanofiber electrodes. The electrochemical reduction of CO2 to CO by using CIS nanofibers coated onto FTO electrodes was carried out for 10 h in total. The observed current density of 0.22 mA cm(-2) and the stability of CIS nanofiber electrodes are found to be competitive with other heterogeneous electrocatalysts. Hence, we believe that the fabrication and application of nanofibrous materials through the electrospinning technique might be of interest for electrocatalytic studies in CO2 reduction.Öğe Investigation of optical framework of chalcostibite nanocrystal thin films: An insight into refractive index dispersion, optical band gap and single-oscillator parameters(ELSEVIER SCIENCE SA, 2017) Yildirim, Murat; Aljabour, Abdalaziz; Sarilmaz, Adem; Ozel, FarukHerein, we report the synthesis of chalcostibite ( CuSbS2) nanocrystals based on hot injection method and the characterization of CuSbS2 thin films by spin coating technique. The deposited films were subjected to the UV-Vis spectrophotometer, XRD, TEM and SAED for optical, structural, morphological and elemental analysis. XRD pattern showed that CuSbS2 nanocrystals have chalcostibite structures and SAED diffraction spots supported the XRD results. Different optical parameters like extinction coefficient, refractive index, real and imaginary parts of dielectric constant and surface and volume energy loss functions have been calculated applying single term Sellmeier dispersion relation and Wemple eDiDomenico single oscillator model. The obtained results are discussed in detail. The optical dispersion and dielectric properties of the CuSbS2 have been determined by the transmittance and reflectance modes in the range of 300-1600 nm. Thus, the CuSbS2 is transparent up to 40-45% in the visible range. The optical bandgap determined by the optical absorbance spectrum analysis showed that thin films possess direct bandgap of 1.86 eV. The calculated refractive index of thin film varies between 1.76 and 2.11 throughout the spectral region considered. The results presented here permit a better understanding of the properties of the chalcostibite nanocrystals which in turn result in the design of more efficient solar cells. (C) 2017 Elsevier B. V. All rights reserved.Öğe Investigation of structural, optical and dielectrical properties of Cu2WS4 thin film(SPRINGER, 2017) Yildirim, Murat; Ozel, Faruk; Sarilmaz, Adem; Aljabour, Abdalaziz; Patir, Imren HatayTernary I-Cu2WS4 were synthesized based on hot-injection process and their thin films are prepared by spin coating techniques at ambient temperature. The energy dispersive analysis of X-rays of the thin films confirmed that synthesized thin film is stoichiometric. Transmittance and reflectance have been used to determine the optical, dispersion and dielectric properties of the Cu2WS4 in the range of 200-2400 nm. The transparency of the Cu2WS4 is 40-45% in the visible range. Optical dispersion parameters have been calculated by using the single term Sellmeier dispersion relation and Wemple-DiDomenico single oscillator model. Several dispersion parameters were determined by the analysis of refractive index dispersion.Absorption coefficient (alpha), extinction coefficient (), the Urbach energy (), real and imaginary parts of dielectric constant (epsilon) and surface and volume energy loss function have been calculated. The optical bandgap determined by the optical absorbance spectrum analysis showed that thin films possess a direct bandgap of 1.74 eV.Öğe L-lysine derived nickel nanoparticles for reductive degradation of organic dyes(VBRI Press, 2016) Khaskheli, Abdul Rauf; Naz, Saba; Soomro, Razium Ali; Özül, Faruk; Aljabour, Abdalaziz; Kalwar, Nazar Hussain; Mahesar, Abdul Waheed; Patır, Hatay İmren; Ersöz, MustafaThis report demonstrates a facile and green fabrication method for the nickel nanoparticles using L-lysine as an efficient protecting agent. The application of green amino acid (L-lysine) enabled formation highly spherical and well-dispersed nanoparticles with average diameter in the range of 10 ±2.5 nm. UV-Vis spectroscopy was used as a primary tool to elaborately study and optimize the necessary experimental condition for the developed synthetic protocol. Fourier transform infrared spectroscopy (FTIR) was used to confirm the surface protection of Ni NPs via L-lysine molecules whereas; atomic force microscopy (AFM) and scanning electron microscopy (SEM) provided morphological and topographical view of the as-synthesized Ni NPs. In addition, small angle X-ray scattering (SAXS) and X-ray diffraction (XRD) were used to evaluate compositional characteristics of fabricated L-lysine protected Ni NPs. The as-synthesized Ni NPs demonstrated excellent catalytic potential when utilized as heterogeneous catalyst for reduction of methylene Blue (MB) in the presence of sodium borohydride (NaBH4). The observed catalytic reaction was determined to follow pseudo first order kinetics with rate constant (K) and turn over frequency (TOF) determined to be 0.0224 and TOF value of 0.00411 s-1 respectively. © 2016 VBRI Press.Öğe Nanofibrous cobalt oxide for electrocatalysis of CO2 reduction to carbon monoxide and formate in an acetonitrile-water electrolyte solution(ELSEVIER SCIENCE BV, 2018) Aljabour, Abdalaziz; Coskun, Halime; Apaydin, Dogukan Hazar; Ozel, Faruk; Hassel, Achim Walter; Stadler, Philipp; Sariciftci, Niyazi SerdarThe electrocatalytic reduction of carbon dioxide (CO2) is an attractive option to efficiently bind electrical energy from renewable resources in artificial carbon fuels and feedstocks. The strategy is considered as crucial part in closing the anthropogenic carbon cycle. In particular, the electrosynthetic production of Cl species such as carbon monoxide (CO) would radiate immense power, since these building blocks offer a versatile chemistry to higher carbon products and fuels. In the present study we report the exploration of the catalytic behavior of semiconducting Co3O4 nanofibers for the conversion of CO2 to CO predominantly with a Faradaic efficiency of 65%. We assist the process by expanding the electrode network with nanofibrous interconnections and hence are able to demonstrate the electrosynthesis of CO without applying any metal supplement. We use polyacrylnitrile (PAN) as template polymer to generate highly crystalline Co3O4 fibers to expand the catalytically active surface to volume ratio. The stability of the nanofibrous electrodes remains for 8 h at a geometric current density of approximately 0.5 mA/cm(2) on a flat surface. The ease of synthesis and the comparatively high Faradaic yield for CO makes Co3O4 nanofibers a potential candidate for future large scale electrode utilization.Öğe NiO and Co3O4 nanofiber catalysts for the hydrogen evolution reaction at liquid/liquid interfaces(PERGAMON-ELSEVIER SCIENCE LTD, 2018) Yanalak, Gizem; Aljabour, Abdalaziz; Aslan, Emre; Özel, Faruk; Patır, İmren Hatay; Kus, Mahmut; Ersöz, MustafaThe development of the non-precious, earth abundant and inexpensive catalysts with high catalytic efficiency for the electrocatalytic hydrogen evolution reaction acts an essential role in sustainable energy conversion and storage. Herein, we report that hydrogen evolution in two-phase systems by an organic soluble electron donor decamethylferrocene (DMFc) has been efficiently catalyzed by Co3O4 and NiO nanofiber catalysts, which are fabricated by the low-cost and simple electrospinning method. The catalytic activities of these metal oxide nanofibers have been examined by two-phase reactions and four-electrode cyclic voltammetry methods at water/1,2 dichloroethane interface. The hydrogen evolution reaction rate of nanofiber catalysts is also compared to the bulk forms of these metal oxide catalysts. The reaction rate is increased 74, 152, 284 and 384 times by using bulk and nanofiber forms of Co3O4 and NiO, respectively, when compared to an uncatalyzed reaction. The higher catalytic activity of the metal oxide nanofibers can be ascribed to the enhanced surface to volume ratio revealed from the fibrous structures. (c) 2018 Elsevier Ltd. All rights reserved.Öğe Penternary chalcogenides nanocrystals as catalytic materials for efficient counter electrodes in dye-synthesized solar cells(NATURE PUBLISHING GROUP, 2016) Ozel, Faruk; Sarilmaz, Adem; Istanbullu, Bilal; Aljabour, Abdalaziz; Kus, Mahmut; Sonmezoglu, SavasThe penternary chalcogenides Cu2CoSn(SeS)(4) and Cu2ZnSn(SeS)(4) were successfully synthesized by hot-injection method, and employed as a catalytic materials for efficient counter electrodes in dye-synthesized solar cells (DSSCs). The structural, compositional, morphological and optical properties of these pentenary semiconductors were characterized by X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), energy-dispersive spectrometer (EDS) and ultraviolet-visible (UV-Vis) spectroscopy. The Cu2CoSn(SeS)(4) and Cu2ZnSn(SeS)(4) nanocrystals had a single crystalline, kesterite phase, adequate stoichiometric ratio, 18-25 nm particle sizes which are forming nanospheres, and band gap energy of 1.18 and 1.45 eV, respectively. Furthermore, the electrochemical impedance spectroscopy and cyclic voltammograms indicated that Cu2CoSn(SeS)(4) nanocrystals as counter electrodes exhibited better electrocatalytic activity for the reduction of iodine/iodide electrolyte than that of Cu2ZnSn(SeS)(4) nanocrystals and conventional platinum (Pt). The photovoltaic results demonstrated that DSSC with a Cu2CoSn(SeS)(4) nanocrystals-based counter electrode achieved the best efficiency of 6.47%, which is higher than the same photoanode employing a Cu2ZnSn(SeS)(4) nanocrystals (3.18%) and Pt (5.41%) counter electrodes. These promising results highlight the potential application of penternary chalcogen Cu2CoSn(SeS)(4) nanocrystals in low-cost, high-efficiency, Pt-free DSSCs.Öğe Photocatalytic Hydrogen Evolution by Oleic Acid-Capped CdS, CdSe, and CdS0.75Se0.25 Alloy Nanocrystals(WILEY-V C H VERLAG GMBH, 2014) Aslan, Emre; Birinci, Okan; Aljabour, Abdalaziz; Ozel, Faruk; Akin, Ilker; Patir, Imren Hatay; Kus, MahmutPhotocatalytic generation of hydrogen by using oleic acid-capped CdS, CdSe, and CdS0.75Se0.25 alloy nanocrystals (quantum dots) has been investigated under visible-light irradiation by employing Na2S and Na2SO3 as hole scavengers. Highly photostable CdS0.75Se0.25 alloy nanocrystals gave the highest hydrogen evolution rate (1466 mu molh(-1) g(-1)), which was about three times higher than that of CdS and seven times higher than that of CdSe.Öğe Urchin-like cobalt nanostructures for catalytic degradation of nitro anilines(VBRI Press, 2016) Khaskheli A.R.; Naz, Saba; Ozul, F.; Aljabour, Abdalaziz; Mahesar S.A.; Patır, I.H.; Ersöz MustafaThe undertaken study describes synthesis of urchin-like Cobalt nanostructures (Co NSs) in aqueous solution using gallic acid as both reductant and protecting agent for the catalytic degradation of 4-methyle-2-nitroaniline. UV-Visible (UV-Vis) spectroscopy was used as a primary tool to elaborately study and optimizes the necessary experimental condition for the developed synthetic protocol Fourier transform infrared (FTIR) spectroscopy showed the interaction between gallic acid and the surface of Co NSs via -OH linkages although Scanning electron microscopy (SEM) confirmed the formation of urchin shaped nanostructures with diameter in the range of 80-110 nm and length of tentacles between 1.0 - 1.8 ?m. The as-synthesized Co NSs proved to be excellent heterogeneous catalyst for the 100 % reductive degradation of 4-methyle-2-nitroaniline in just 60 sec in presence of reductant (NaBH4) with reaction rate calculated to follow pseudo first order kinetic and rate constant of 0.055s-1. Furthermore, Co NSs, showed excellent recyclability and were reused four times for the degradation of 4-methyle-2-nitroaniline with efficiency that displayed negligible catalytic poisoning. © 2016 VBRI Press.
