Energy storage properties of symmetric and unsymmetric meso-aryl porphyrin derivatives on carbon felt electrode

Porphyrins are macrocyclic compounds made up of four pyrrole rings connected by methine bridges. The delocalised π-conjugation on the tetrapyrrole rings allows efficient electron transfer and high electronic conductivity, making porphyrin derivatives ideal for electrode materials in energy storage devices. This study investigates the capacitance properties of symmetric (SY4) and asymmetric (SY2) meso-aryl porphyrin derivatives using modified carbon felt electrodes (CFE). Electrochemical measurements in acidic, basic, and neutral solutions were performed to determine the most effective working medium. After understanding the energy storage mechanisms for SY2/CFE and SY4/CFE, a series of electrochemical tests were conducted to determine the specific capacitance values of both materials. Cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge-discharge techniques were used to evaluate capacitive performance. CV data showed maximum specific capacitances of 158 F/g (at 5 mV/s) for SY2/CFE and 326 F/g (at 1 mV/s) for SY4/CFE. At 0.5 A/g, the specific capacitance values were 336 F/g for SY2/CFE and 63 F/g for SY4/CFE. The maximum energy density for SY2/CFE was 184 Wh/kg, while SY4/CFE had a maximum power density of 1890 W/kg. Stability tests showed a 68% performance retention for SY4/CFE and a 56% increase for SY2/CFE after 500 cycles.