Structurally Dependent Electrochemical Properties of Ultrafine Superparamagnetic ‘Core/Shell’ γ-Fe2O3/Defective α-Fe2O3 Composites in Hybrid Supercapacitors

Materials

Oleg Bazaluk¹  Andrii Koveria²  Vasyl Lozynskyi³  Yurii Yavorskyi⁴  Andrii Hrubiak⁵  Volodymyr Moklyak⁵  Serhii Fedorov⁶  Lina Kieush⁶  Bogdan Rachiy⁷  Maria Moklyak⁷  Ivan Gasyuk⁷ 

[1] Belt and Road Initiative Institute for Chinese-European Studies (BRIICES), Guangdong University of Petrochemical Technology, Maoming 525000, China;Department of Chemistry, Dnipro University of Technology, 49005 Dnipro, Ukraine;Department of Mining Engineering and Education, Dnipro University of Technology, 49005 Dnipro, Ukraine;Department of Physical Materials Science and Heat Treatment, National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”, 35 Politekhnichna Str., 03056 Kyiv, Ukraine;G.V. Kurdyumov Institute for Metal Physics of the N.A.S. of Ukraine, 36 Academician Vernadsky Boulevard, 03142 Kyiv, Ukraine;National Metallurgical Academy of Ukraine, 4 Gagarin Av., 49600 Dnipro, Ukraine;The Faculty of Physics and Technology, Vasyl Stefanyk Precarpathian National University, 56 Shevchenko Str., 76018 Ivano-Frankivsk, Ukraine;

关键词: ultrafine composite;    Mossbauer spectroscopy;    phase composition;    superparamagnetism;    defective structure;    capacity;   

DOI  :  10.3390/ma14226977

来源: DOAJ

【 摘 要 】

The paper presents a method for obtaining electrochemically active ultrafine composites of iron oxides, superparamagnetic ‘core/shell’ γ-Fe₂O₃/defective α-Fe₂O₃, which involved modifying sol-gel citrate synthesis, hydrothermal treatment of the formed sol, and subsequent annealing of materials in the air. The synthesized materials’ phase composition, magnetic microstructure, and structural, morphological characteristics have been determined via X-ray analysis, Mossbauer spectroscopy, scanning electron microscopy (SEM), and adsorption porometry. The mechanisms of phase stability were analyzed, and the model was suggested as FeOOH → γ-Fe₂O₃ → α-Fe₂O₃. It was found that the presence of chelating agents in hydrothermal synthesis encapsulated the nucleus of the new phase in the reactor and interfered with the direct processes of recrystallization of the structure with the subsequent formation of the α-Fe₂O₃ crystalline phase. Additionally, the conductive properties of the synthesized materials were determined by impedance spectroscopy. The electrochemical activity of the synthesized materials was evaluated by the method of cyclic voltammetry using a three-electrode cell in a 3.5 M aqueous solution of KOH. For the ultrafine superparamagnetic ‘core/shell’ γ-Fe₂O₃/defective α-Fe₂O composite with defective hematite structure and the presence of ultra-dispersed maghemite with particles in the superparamagnetic state was fixed increased electrochemical activity, and specific discharge capacity of the material is 177 F/g with a Coulomb efficiency of 85%. The prototypes of hybrid supercapacitor with work electrodes based on ultrafine composites superparamagnetic ‘core/shell’ γ-Fe₂O₃/defective α-Fe₂O₃ have a specific discharge capacity of 124 F/g with a Coulomb efficiency of 93% for current 10 mA.

【 授权许可】

Unknown