High performing supercapacitors using Cr2O3 nanostructures with stable channels- theoretical and experimental insights

Abstract

Cr2O3 is considered to be a promising cathodic material for supercapacitor applications on the account of its fast redox kinetics, mesoporous structure, and high electrochemical stability. Using a one-step synthesis of Cr2O3, a unique cactus-like morphology can be easily obtained. Such particles improve the specific surface area and electrolyte ion diffusion, leading to enhanced capacitance values. The prepared cactus-like (Cr2O3-c) particles are able to return a specific capacitance of 68 F/g at 5 mV s−1, in three-electrode measurement. This can be attributed to the redox couple of Cr4+/ Cr3+ displayed by Cr2O3 at the electrode–electrolyte interface. Further, the electrochemical performance of cactus-like Cr2O3 material (Cr2O3-c) and solid Cr2O3 spheres (Cr2O3-s) is also compared. This study proves that much superior performance is delivered by protruded nanoparticles. The spikes on the top of the particle surface ensures that two particles are well separated, which stimulates stable channels for ion intercalation–deintercalation. The physics can be explained using a modified free electron model for three-dimensional lattice. Further, using density functional theory (DFT) calculations the electronic band structure, density of states (DOS) and their influence on the electrochemical performance of Cr2O3 are evaluated.