Yazar "Coskun, Halime" seçeneğine göre listele

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    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, Mahmut
    Selective 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.
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    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 Serdar
    The 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.