Dynamic electrochemical impedance spectroscopy as a rapid screening tool for supercapacitor electrode materials

摘要

Discovering novel materials and rapid screening for its suitability in electrochemical energy systems needs to adopt a simple and time-effective characterization method in the device manufacturing sector. In the present work, an agricultural waste material has been used as a precursor to synthesize a novel porous carbon aerogel using a facile process. The surface area and pore size distribution of the carbon aerogel has been optimized by varying carbonization temperature. For the first time, the dynamic electrochemical impedance spectroscopy (DEIS) technique was used to evaluate the electrochemical performance of the carbon electrodes and compared to conventional electrochemical techniques. This technique identified the best performing electrode material based on double-layer capacitance (C_(dl)) and charge transfer resistance (R_(ct)) during electrochemical process. The dynamic change in C_(dl) and R_(ct) values with applied potential depends on charge formation and its kinetics, which can provide direct information about the specific capacitance and capacitance retention of carbon aerogels that can only be obtained from cyclic voltammetry (CV) and galvanostatic charge-discharge methods (GCD). In order to validate the DEIS results, the CV and GCD experiments were also performed. The GCD results showed a maximum specific capacitance value of 191 F g~(-1) at 0.5 A g~(-1) for the high-performing samples identified through DEIS, also 87% of capacitance was retained at a high current density value of 5 A g~(-1). Also, the changes in C_(dl) and R_(ct) values were compared with textural properties such as surface area and pore size distribution of the carbon aerogels. From DEIS, it was clearly evident that the specific capacitance and capacitance retention majorly depends on the presence of micro- and mesopores of the material. This result concludes that required parameters on textural and electrochemical properties of the material can be attained by carrying DEIS, which can accelerate material screening efficiently.