Electropolymerized porphyrin films as active materials in organic supercapacitors. A study of the effect of different central metals

Abstract

Four metallized (Zn, Co, Cu) and non-metallized AA-BB substituted porphyrins were used in the electrochemical synthesis of redox-conjugated polymers, formed as electroactive organic conducting films over solid substrate. Electrochemical and spectroelectrochemical characterization shows that these materials can undergo several (thousands) oxidation–reduction cycles without degradation or desorption from the electrode surface. Also, the electrochemical response and the spectral changes demonstrate that all the electroactive species present in the materials (tetrapirrolic ring, tetraphenylbenzidine and dicarbazole) are involved in fully reversible redox processes. Because of this, the supercapacitive capacity of these polymeric materials was analyzed. Constant current charge–discharge cycles and electrochemical impedance spectroscopy showed that the copper porphyrin-based polymer exhibited the highest gravimetric capacitance (332 F g−1), being also the material with the largest superficial roughness parameters, analyzed by atomic force microscopy. Using Cu(II) porphyrin dendrimeric polymer as active material, an electrochemically generated organic polymer-based supercapacitive device was assembled with a gelled-composited electrolyte.