Browsing by Author "Sheidaei, Yasaman"

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Open Access
Application of covalent organic framework based on porphyrin and cucurbit[6]uril as a bifunctional electrocatalyst for hydrogen and oxygen evolution
(2021-01) Sheidaei, Yasaman
There is great apprehension about consumption of fossil fuels as well as the corresponding environmental issues which has evoked supreme efforts worldwide to develop clean and sustainable energy sources. Electrocatalytic water splitting producing both hydrogen and oxygen gas has shown considerable potential for energy conversion as hydrogen can meet the requirements for future energy demands. Hence it is of utmost importance to introduce novel electrocatalysts to overcome energy barriers for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Here this thesis highlights the synthesis and characterization of a novel supramolecular assembly of cucurbit[6]uril and porphyrin and also examines its electrocatalytic activity toward both HER and OER. Electrochemical studies such as linear sweep voltammetry, chronoamperometry, chronopotentiometry, electrochemical impedance spectroscopy were performed to investigate the activity of the catalyst. The structural and morphological properties of sample were also studied using scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FT-IR). It was observed that the catalyst was able to show excellent electrocatalytic activity with onset potentials of -0.25 V (for HER) and 1.6 V (for OER) while producing 18.7 and 14.92 mmol.gr-1.hr-1 hydrogen and oxygen gas with faradaic efficiencies of 85% and 99%, respectively.
Open Access
Covalent organic framework constructed by clicking azido porphyrin with perpropargyloxy-cucurbit[6]uril for electrocatalytic hydrogen generation from water splitting
(American Chemical Society, 2021-04-26) Khaligh, Aisan; Sheidaei, Yasaman; Tuncel, Dönüş
In the present study, we describe the synthesis and characterization of a new covalent organic framework (COF-TPP-CB[6]) which was assembled together by clicking perpropargyloxy cucurbit[6]uril (CB[6]) to the azido-functionalized tetraphenylporphyrin (TPP-4N3) through a copper-catalyzed azide–alkyne cycloaddition reaction (CuAAC). Perpropargyloxy CB[6] was synthesized through the direct oxidation of CB[6] to afford perhydroxy CB[6] followed by subsequent O-propargylation using NaH. We also demonstrated that the resulting framework (COF-TPP-CB[6]) can be employed as an efficient and stable electrocatalyst for hydrogen evolution reaction (HER) in alkaline medium upon loading it with a nickel cocatalyst. The effect of TiO2 and different loadings of Ni on the HER performance of TPP-CB[6] was also studied. Herein, 12%Ni@TPP-CB[6] as the optimum catalyst showed an impressive H2 production rate of 18.7 mmol h–1 g–1 with a low onset potential of −250 mV.
Open Access
In situ-Electrochemically reduced graphene oxide integrated with cross-linked supramolecular polymeric network for electrocatalytic hydrogen evaluation reaction
(Elsevier, 2021-08-26) Aoudi, Bouthaina; Khaligh, Aisan; Sheidaei, Yasaman; Tuncel, Dönüş
Herein, we report the synthesis of a new supramolecular polymeric network (PCN) assembled through crosslinking of propyl bromide substituted tetraphenyl porphyrin with perhydroxy-cucurbit [8]uril and its use in the electrocatalytic hydrogen evaluation reaction after loading with nickel and integrating with in situ-electrochemically reduced graphene oxide (ERGO). Electrode was prepared by first coating graphene oxide on the FTO substrate followed by layering the nickel loaded PCN and finally by applying an appropriate voltage to reduce the graphene oxide in situ electrochemical reaction. The loading of nickel cocatalyst into PCN together with the integration of ERGO layer substantially improved its HER efficiency. Effect of various concentrations of Ni and GO on the HER activity of the developed electrocatalyst were investigated. Therein, ERGO1/Ni2@PCN catalyst containing 41% Ni and 50% GO (with respect to PCN) with only one layer of each component demonstrated excellent HER activity and stability with low onset and overpotentials of −20 mV, η@10 mA cm−2 of −360 mV, respectively, and remarkable hydrogen generation rate of 27.5 mmol h−1 g−1 in 1 M KOH. This noble-metal-free catalytic system is simple yet highly promising for the efficient hydrogen evolution reaction from water splitting.