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

RAUL RUBIO1*, JAVIER DURANTINI1, DANIEL HEREDIA2, EDGARDO DURANTINI2, LUIS OTERO1, MIGUEL GERVALDO.

Warsaw

Encuentro; E-MRS 2021 Fall Meeting Symposium B: Battery and Energy Storage Devices: from materials to eco-design; 2021

Renewable energy sources, such as solar radiation, are alternatives to supplant fossil fuels. However, because of the variability in time as well as geographic distribution, devices to storethe generated energy are needed. Supercapacitors can store the energy generated by other energy sources and deliver it when necessary. There are two types of supercapacitors: electrostatic double layer (EDLC) and pseudocapacitors (PSC). PSC store energy by faradaic reversible redox processes (oxidation-reduction) that occur within the electrode material, being this phenomenon known aspseudocapacitance. Until now metal oxides, metal hydroxides and organic polymers have been used in PSC. Organic polymers present high specific energy and power, high conductivities and are flexible. However, most of these organic polymers are synthetized by complex chemical methods involving several steps which are expensive and also generate waste. A strategy that can be used in the deposition of organic polymers is the electropolymerization. Electropolymerization is a very versatile procedure to construct organic films over metallic contacts, or over transparent conducting oxides. By electing the correct polymerization group and the correct desired functionality, a significative number of monomers can be designed and synthetized to generate polymers. In this work we present the electrochemical formation and characterization of porphyrin films obtained by electrochemical polymerization. The used porphyrin monomers have two carbazole and two triphenylamine electroactive groups, which were chosen to undergo electrochemical initiated radical coupling that promotes the formation of polymeric structures. Also, two central hydrogen atoms were substituted with different central metals (Zn (II), Co (II), Cu (II)). The monomers and the electrogenerated films were characterized by cyclic voltammetry, UV-vis spectroscopy, AFM, SEM and Electrochemical Impedance Spectroscopy (EIS).Because of the reversible oxidation-reduction processes involving the porphyrin macrocycle, the dicarbazole and the tetraphenylbenzidine groups present in the polymeric structure, it was expected a pseudocapacitive behavior that would make the porphyrin films adequate for their use as active material in the construction of supecapacitors. The porphyrin films were characterized by chargedischarge cycles at different current densities. The discharge and charge curves were nearly mirror images, indicating a fast and reversible electron exchange. The pseudocapacitive electrodematerials exhibited capacitances as high as 201 F/g at a currentKEY Symp Subject View All Actiondensity of 2 A/g. These high capacitances demonstrate that the porphyrin films are promising materials for energy storage applications where a high discharge-recharge rate is needed.