ScholarWorks@동국대학교

초록

The rational design of electrode materials with tailored composition and architecture is crucial for advancing high-capability electrochemical energy storage systems. This study reports that gadolinium-modified NiFe2O4 nanosheet electrodes were effectively synthesized on nickel foam via a hydrothermal approach followed by thermal treatment. A series of compositions (NiFe, NiFe-Gd1, NiFe-Gd2, and NiFe-Gd3) were prepared to systematically examine the effect of Gd incorporation on structural features and electrochemical properties. X-ray diffraction (XRD) analysis confirmed the formation of the cubic spinel NiFe2O4 phase without detectable secondary phases, indicating that the crystal structure remains intact after Gd introduction. X-ray photoelectron spectroscopy (XPS) further verified the presence of Ni2+, Fe3+, and Gd3+ species within the lattice environment. Morphological analysis using field-emission scanning electron microscopy (FESEM) revealed a nanosheet-based architecture, where the optimized NiFe-Gd2 electrode exhibited a porous and interconnected nanosheet framework with abundant exposed edges. This structural configuration improves electrolyte penetration and facilitates efficient ion transport during charge storage processes. Electrochemical measurements demonstrated that the NiFe-Gd2 electrode delivers an areal capacitance of 5235 mF cm(-2) at 10 mA cm(-2), along with improved reaction kinetics and low internal resistance. An asymmetric supercapacitor assembled using NiFe-Gd2 as the positive electrode and activated carbon as the negative electrode operated stably within a 0-1.5 V potential window, achieving an energy density of 0.136 mWh cm(-2) and a power density of 3.14 mW cm(-2)<bold>,</bold> while retaining 86.55% of its initial capacitance after 7000 cycles. These results highlight the potential of rare-earth engineering as a viable strategy for designing advanced spinel ferrite electrodes and pave the way for the development of high-performance, durable, and scalable supercapacitor systems for practical energy storage applications.

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