Department of Chemistry

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Browsing Department of Chemistry by Author "Akbari, Sina Sadigh"

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    Cobalt borophosphate on nickel foam as an electrocatalyst for water splitting
    (Elsevier BV, 2022-06-10) Ülker, E.; Akbari, Sina Sadigh; Karadas, Ferdi
    One of the most critical steps in the transition to carbon-free energy systems is sustainable hydrogen evolution from water. In this research, a cobalt borophosphate crystalline compound consisting of phosphate and borate anions was synthesized with a solid-state reaction. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and X-ray Photoelectron (XPS) was employed to investigate the structure, composition, and morphology of Co3BPO7. Electrocatalytic performances of the catalyst towards oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) have been investigated on nickel foam (NF) electrode in 1.0 M KOH (pH 13.6) by linear sweep voltammetry, chronopotentiometry, cyclic voltammetry, and electrochemical impedance spectroscopy. For OER, the catalyst exhibits an overpotential of 230 mV at 10 mA cm−2 with a Tafel slope of 130 mV dec−1, which is comparable to that of the benchmark RuO2 electrocatalyst, and 220 mV overpotential for a current density of 10 mA cm−2 with a Tafel slope of 147 mV dec−1 for HER process. Long-term chronoamperometry and multiple cyclic voltammetric experiments indicate the catalyst is stable throughout both HER and OER processes. Electrochemical experiments and characterization studies performed on the pristine and post-catalytic electrode indicate that the catalyst is robust under alkaline electrocatalytic conditions (pH 13.6).
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    Effect of cobalt doping on photocatalytic water splitting activity of NiTi-layered double hydroxide
    (Royal Society of Chemistry, 2022-03-17) Samuei, Sara; Akbari, Sina Sadigh; Ülker, E.; Karadaş, Ferdi
    Metal doping has been used as an effective strategy to tune the energy levels of semiconductors. Herein, we dope NiTi layered double hydroxide (NiTi-LDH) with cobalt to prepare a ternary LDH, CoNiTi-LDH, to enhance its photocatalytic performance towards both water oxidation and hydrogen evolution. A CoNiTi-LDH with smaller plate sizes and a higher degree of order is obtained, which allows the band gap to shrink from 2.7 eV to 2.4 eV. CoNiTi-LDH exhibits a photocatalytic water oxidation activity of 366 μmol g−1 h−1, which is more than two times higher than NiTi-LDH (166 μmol g−1 h−1). We observed that appropriate energy levels of CoNiTi-LDH allow it to be an efficient photocatalyst also for hydrogen evolution. We performed detailed characterization studies to elucidate the effect of Co-doping on photocatalytic activity.
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    Precious metal‐free photocatalytic water oxidation by a layered double hydroxide‐Prussian blue analogue hybrid assembly
    (Wiley-VCH Verlag, 2020-11) Akbari, Sina Sadigh; Karadaş, Ferdi
    The development of earth‐abundant photocatalytic assemblies has been one of the bottlenecks for the advancement of scalable water splitting cells. In this study, a ZnCr layered double hydroxide and a CoFe Prussian blue analogue are combined to afford an earth‐abundant photocatalytic assembly involving a visible light‐absorbing semiconductor (SC) and a water oxidation catalyst (WOC). Compared to bare ZnCr‐LDH, the SC‐WOC hybrid assembly exhibits a threefold enhancement in photocatalytic activity, which is maintained for 6 h under photocatalytic conditions at pH 7. The band energy diagram was extracted from optical and electrochemical studies to elucidate the origin of the enhanced photocatalytic performance. This study marks a straightforward pathway to develop low‐cost and precious metal‐free assemblies for visible light‐driven water oxidation.
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    Selective photocatalytic CO2 reduction by cobalt dicyanamide
    (Royal Society of Chemistry, 2022-07-29) Akbari, Sina Sadigh; Karadaş, Ferdi
    Photocatalytic conversion of CO2 into chemical fuels is a promising approach to tackle carbon emission and global warming. Herein, we promote a cobalt dicyanamide coordination compound, Co-dca, for the first time, as a selective catalyst to reduce CO2 to CO in the presence of a ruthenium photosensitizer (Ru PS) under visible light irradiation. Co-dca was prepared by a facile precipitation method and characterized by Infrared, UV-Vis, XRD, SEM, TEM, and XPS studies. A series of photocatalytic experiments under various reaction conditions were performed to reveal the role of the PS, the scavenger, and the solvent in the selectivity and the activity of the photocatalytic process. We find that Co-dca exhibits an activity of 254 μmol h−1 g−1 and a CO selectivity as high as 93%.