Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Nanohybridization of POM/CNT Anode Materials for Enhanced Cycle Stability and Superior Discharge Capacity in Sodium-Ion Batteries(Elsevier Science SA, 2025) Chilufya, Langson; Bugday, Nesrin; Yasar, Sedat; Emirdag-Eanes, MehtapPolyoxometalates (POMs) have emerged as high-energy-density electrodes acting as 'electron/ion sponges' for pseudocapacitive energy storage, attributed to their swift and reversible multi-redox reactions. In sodium-ion batteries (SIBs), POM-based electrodes have given excellent energy density. However, the negligible conductivity of pristine POMs and high electrolyte dissolution can lead to subpar electrochemical performance in poor capacity retention, and rate capability. To address these challenges, we employed a facile ultrasonication strategy to prepare polyoxometalate/carbon-nanotube (POM/CNT) nanohybrids. CNTs were modified with the tetrabutylammonium polyoxotungstate, TBA3[PW12O40].nH2O (TBA-PW12), yielding TBA-POM/CNT nanohybrids. These were synthesized using four CNT sources: single-walled (SW), multi-walled (MW), and their hydroxyl-functionalized analogues (SWOH and MWOH). The nanohybrids were characterized using FT-IR, Raman spectroscopy, powder XRD, TGA, SEM/EDX, STEM, XPS, and BET analysis. Electrochemical evaluation of TBA-PW12/SW and TBA-PW12/MW nanohybrids as an anode for SIB showed superior Na-ion storage, delivering reversible capacities of 69.4 mAh g-1 and 27.5 mAh g-1, respectively, at a current density of 2 A g-1 after 1000 cycles. Under the same conditions, the nanohybrids from functionalized SWOH and MWOH also showed enhanced performance, achieving discharge capacities of 66.2 mAh g-1 and 57.3 mAh g-1, respectively. This impressive electrochemical performance was ascribed to the multiple active sites of TBA-PW12 combined with conductive pathways and surface functionalities of CNTs, which enable rapid electron transfer, high Na-ion conductivity, and efficient ion diffusion. Overall, POM/CNT nanohybridization presents a promising strategy to overcome the intrinsic limitations of pristine POMs, thereby advancing the design of high-performance anodes for SIBs and sustainable energy applications.Article Citation - WoS: 2Citation - Scopus: 2Investigation on the Keggin Anchored on Hydroxide-Functionalized Single-Walled Carbon Nanotubes as Superior Cathode for Aqueous Zinc-Ion Batteries(American Chemical Society, 2025) Chilufya, Langson; Sertbaş, Vahide; Aytekin, Ahmet; Karabudak, Engin; Emirdag-Eanes, MehtapRechargeable aqueous zinc-ion batteries (AZIBs) have become a viable option in electrochemical energy storage systems (EESS) owing to their inherent safety features and economic friendliness. Nonetheless, creating suitable cathode materials for AZIBs with high structural stability, good rate performance, and great capacity remains a significant challenge. Polyoxometalate (POM)-based nanohybrid materials have shown promising results in high cycling stability and great specific capacity. However, POMs susceptible to electrolyte dissolution and the sluggish Zn-ion (Zn2+) kinetics have significantly hampered their electrochemical performance as cathodes for AZIBs. Herein, we present a Keggin POM, K<inf>3</inf>[PW<inf>12</inf>O<inf>40</inf>]·nH<inf>2</inf>O (KPW<inf>12</inf>), anchored on hydroxyl (OH)-functionalized single-walled carbon nanotubes (SWOH) that were fabricated via a facile ultrasonication procedure. Employed as cathodes for AZIBs, the optimal KPW<inf>12</inf>/SWOH feature exhibited remarkable electrochemical performance. The system satisfied the Zn2+storage, achieving a reversible discharge capacity of 183 mAh g–1at a high current density of 5C with a flat and long discharge plateau after 160 cycles. The perfect synergistic contribution of the pseudocapacitive nature of the super-reduced state of KPW<inf>12</inf>and the electron-conductive network of SWOH was attributed to this exceptional electrochemical performance. Furthermore, the presence of oxygen in SWOH enhanced the transfer kinetics of electrons and smooth Zn2+diffusion while lowering the Zn2+migration energy barrier by providing more accessible active sites. This demonstrates remarkable promise in fabricating robust electrode materials optimized for integration within aqueous battery systems that pave the way for further research into POM-based materials for EESS. © 2025 Elsevier B.V., All rights reserved.Article Citation - WoS: 1Citation - Scopus: 1Hydrothermal Synthesis, Characterization and Catalytic Activities of a Keggin Structure of (4,4′-Bpyh2)3[pw12o40]2•3h2o and a Wells-Dawson Structure of (4,4′-Bpyh2)3(4,4′(Elsevier, 2025) Ece, Ozlem; Chilufya, Langson; McMillen, Colin D.; Emirdag-Eanes, MehtapTwo novel polyoxometalates composed of heteropolytungstates, (4,4 '-bpyH2)3[PW12O40]2 center dot 3H2O (1) and (4,4 '- bpyH2)3(4,4 '-bpyH)1.75[Cu(bpy)2]0.25[H2P2W18O62]2 (2) have been synthesized under hydrothermal conditions and characterized by single crystal X-ray diffraction and TGA methods. Compound 1 crystallizes in the cubic space group Ia-3with a = 25.9356(12) angstrom, b = 25.936(3) angstrom, c = 25.936(3) angstrom, alpha = 90.00, (3= 90.00, gamma= 90.00 and Z = 8, and compound 2 crystallizes in the triclinic space group P-1with a = 13.5194(17) angstrom, b = 22.400(3) angstrom, c = 27.374(4) angstrom, alpha = 79.833(3), (3= 77.439(3), gamma= 80.213(4) and Z = 2. In addition to structural characterization, the catalytic activities of 1 and 2 were determined in hydrolysis reactions. In the catalytic study, starch hydrolysis reactions were performed by using hydrothermal synthesis, and starch was hydrolyzed successfully at 150 degrees C, 5 h, based on the results of Lugol's test, which highest conversion yields above 90 wt.% under optimum reaction conditions. FT-IR analysis and catalyst reusability tests were also performed for each compound. No appreciable loss was observed in activity after five reaction cycles.