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    Hydrogen storage capabilities of ionothermally synthesized covalent triazine frameworks (CTFs)
    (Pergamon-Elsevier Science Ltd, 2023) Ergani, Songul Kaskun; Sonmez, Turgut; Uecker, Jan; Arpa, Beyza; Palkovits, Regina
    Covalent triazine frameworks (CTFs) represent an attractive new type of porous organic compounds demonstrating promising stability, nontoxicity, nitrogen functionalities and adjustable porosity. They have been greatly investigated in various applications; however, the hydrogen storage capacities of CTFs have been poorly described so far. Here, we present hydrogen storage capacities of a series of covalent triazine frameworks based on four different applied monomers (DCP, DCBP, mDCB and pDCB) synthesized via classical ionothermal route (ZnCl2, 400/600 degrees C). Among the synthesized CTFs, DCP shows the highest hydrogen storage capacity of 4.02 wt% at 20 bar, almost two times higher compared to the lowest value of 2.43 wt% for CTF DCBP. Furthermore, the CTF DCP outperforms with a H-2 uptake of 2.95 wt% at 1 bar pressure and 77 K state-of-the-art 2D porous organic polymers and shows very high uptake capability within the reported porous polymer materials. The high hydrogen storage capability of DCP is correlated to the high nitrogen (N) content of 20.4 wt%, high fraction of pyridinic N-sites (50.3%), the largest defect structure, highest crystallinity and microporosity among the synthesized CTFs. The specific surface area (SSA) and the total pore volume (TPV) seem to not have an influential impact on the H(2 )storage capacity as the CTF DCP exhibits the highest H-2 storage capacity with a SSA of 1737 m(2) g(-1) and a TPV of 0.9 cm(3) g(-1), the lowest values among the CTFs.(c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
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    Mechanistic pathways and kinetic studies of oxygen reduction reaction (ORR) at Covalent Triazine Frameworks (CTFs)
    (Pergamon-Elsevier Science Ltd, 2024) Soenmez, Turgut; Uecker, Jan; Hamzah, Hairul Hisham; Palkovits, Regina
    Herein, four different metal-free nitrogen containing Covalent Triazine Frameworks (CTFs) based on their applied monomers (DCP, DCBP, mDCB and pDCB) are synthesized via a classical ionothermal synthesis route (ZnCl2, 400/600 degrees C). These materials are fully characterized and their electrochemical activities for ORR are tested and compared to each other including Carbon Super P and Pt black as standards in 0.1 M KOH. While DCP provides similar catalytic activity to Carbon Super P showing mostly a 2e- process (n=2.95) with high H2O2 formation of 52.6 %, the other three CTFs (DCBP, mDCB and pDCB) possess higher ORR activities, surprisingly even much higher limiting current densities than Pt black, proving that O2 is mainly reduced via direct 4epathway since n values are in the range of 3.52 to 3.62 and the detected H2O2 values are in the range of 19-23.9 %. Among the studied CTFs, mDCB reaches a limiting current density of -5.61 mA cm-2 (1.21 mA cm-2 larger than that for Pt black, -4.40 mA cm-2) with 0.11 V larger onset potential compared to Pt black. The significant electrochemical performances of the CTF materials in ORR via a 4e- process are correlated to the high specific surface areas (up to 2500 m2 g-1), large pore volumes (up to 2.05 cm3 g-1) and the largest total N-graphitic/ quaternary contents as well as micro-mesoporous structure properties.