Biphasic cerium oxide nanoparticles: a dual-functional approach for dielectric and supercapacitor applications
摘要
This research study investigates the synthesis and performance of biphasic cerium oxide nanoparticles (NPs) for supercapacitor applications using a cost-effective and scalable co-precipitation method. A distinctive aspect of this work is the successful fabrication of biphasic CeO2 structures, comprising rhombohedral Ce7O12 (87%) and cubic CeO2 (13%) phases a relatively unexplored combination in energy storage materials. Thermogravimetric and differential thermal analysis (TG/DTA) was employed to evaluate the thermal stability and decomposition behavior of the prepared NPs. Structural and morphological analyses confirmed the phase coexistence, with an average crystallite size of 31.95 nm and a high crystallinity index of 60.52%, contributing to enhanced electrochemical properties. The NPs demonstrated a high surface area-to-volume ratio, moderate porosity (7.4%), and uniform elemental distribution features that are critical and rarely reported together in cerium oxide-based supercapacitor materials. Photoluminescence (PL) and FT-RAMAN spectroscopy revealed their optical properties and vibrational modes, respectively. Optical characterization unveiled a direct bandgap of 3.18 eV and an indirect bandgap of 2.87 eV, with strong UV absorption, further emphasizing their multifunctional nature for optoelectronic and energy storage applications. Dielectric studies highlighted unusually high permittivity and low dielectric loss, affirming the material’s suitability for high-frequency energy devices. Electrochemical evaluations showed an impressive specific capacitance of 520 F g−1 at 10 mV s−1 and 469.54 F g−1 at 1 A g−1, which are among the highest reported values for cerium oxide-based systems synthesized via co-precipitation. The charge storage mechanism was predominantly capacitive (77.51% at. 10 mV s−1), supported by low solution resistance (2.09 Ω) and moderate charge transfer resistance (16.8 kΩ). Additionally, the prepared NPs showed excellent cyclic stability up to 2300 cycles. These findings underscore the novelty of utilizing biphasic cerium oxide NPs with tailored structural and electronic properties as high-performance, cost-effective electrode materials, offering a unique combination of excellent capacitance, energy efficiency, and long-term structural stability for next-generation supercapacitors.