Enhanced electrochemical performance of Ce-MOF/h-CeO2 composites for high-capacitance energy storage applications

Abstract

The escalating demand for energy storage underscores the significance of supercapacitors as devices with extended lifespans, high energy densities, and rapid charge–discharge capabilities. Ceria (CeO₂), known for its exceptional properties and dual oxidation states, emerges as a potent material for supercapacitor electrodes. This study enhances its capacitance by integrating it with Metal–Organic Frameworks (MOFs), carbon-rich compounds noted for their good conductivity. In our research, hollow ceria (h-ceria) is synthesized via hydrothermal methods and amalgamated with Ce-MOF, employing 2,6-dinaphthalene dicarboxylic acid as a ligand, to fabricate Ce-MOF@h-CeO₂ composites. The structural and morphological characteristics of the composite are methodically examined using X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), and Fourier-Transform Infrared (FT-IR) spectroscopy. The band gap of the materials is ascertained through UV-Diffuse Reflectance Spectroscopy (UV-DRS). Electrochemical behavior and redox properties of the Ce-MOF composites are explored using Cyclic Voltammetry (CV), Galvanostatic Charge and Discharge (GCD), and Electrochemical Impedance Spectroscopy (EIS), providing insights into the material's stability. Electrochemical characterization of the composite reveals maximum specific capacitance, energy density and power density are 2643.78 F g⁻¹ at a scan rate of 10 mV s⁻¹, 249.22 W h kg⁻¹, and 7.9 kW kg⁻¹, respectively. Additionally, the specific capacitance of Ce-MOF synthesized with a 2,6-dinaphthalene dicarboxylic acid (NDC) ligand reaches 995.59 F g⁻¹, surpassing that of Ce-MOF synthesized using a 1,3,5-tricarboxylic acid (H₃BTC) ligand. These findings highlight the promising economic potential of high-performance, environmentally sustainable, and cost-effective energy storage devices. The innovative Ce-MOF@h-CeO₂ composite materials at the core of this research pave the way for advancing the field of energy storage solutions.