Electropolymerization of thiazole derivatives bearing thiophene and selenophene and the potential application in capacitors

•Three thiazole derivatives bearing thiophene and selenophene were used as monomers for electropolymerization.•Pseudocapacitor performance of deposited polymer layers was investigated on macroelectrode and ultramicroelectrode.•Pseudocapacitor behavior is related to the anion intercalation/deintercalation processes by faradaic reactions of oligomer chains.•The approximate molecular weight of the solvated anion and the number of solvent molecules surrounding a solvated anion were analyzed. Three thiazole derivatives bearing thiophene and selenophene are synthesized and used as monomers for electropolymerization. The electropolymerization process is studied using cyclic voltammetry (CV) and electrochemical quartz crystal microbalance (EQCM) techniques. Deep understanding is obtained regarding the pseudocapacitor performance of deposited polymer layers by subjecting the macroelectrode and ultramicroelectrode to CV and galvanostatic charging–discharging experiments in three kinds of electrolytes. Notably, the highest specific capacitance is observed in the derivative bearing selenopheno[3,4-d]thiazole and selenophene in a solution of tetrabutylammonium tetrafluoroborate. Furthermore, the electropolymerization rate is influenced by the kind of chalcogenophene and the CV scan rate. A spectroelectrochemistry experiment reveals the optical and electrochromic behavior of the deposited polymer layers. From these results, the pseudocapacitor performance of the deposited polymer layers is related to anion intercalation/deintercalation processes by faradaic reactions of oligomer chains. The EQCM experiments also reveal these processes during electropolymerization and anion intercalation/deintercalation into the deposited polymer layers. Finally, the approximate molecular weight of the solvated anion and the number of solvent molecules surrounding a solvated anion are analyzed using the EQCM data.