A rational experimental approach to identify correctly the working voltage window of aqueous-based supercapacitors

Autor(es)

Nunes, Willian G. ^[1] ; Freitas, Bruno G. A. ^[1] ; Beraldo, Renato M. ^[1] ; Maciel Filho, Rubens ^[2] ; Da Silva, Leonardo M. ^[3] ; Zanin, Hudson ^[1]

Afiliação do(s) autor(es)

^[1] Univ Estadual Campinas, Ctr Innovat New Energies, Carbon Scitech Labs & Mfg Grp, Adv Energy Storage Div, Sch Elect & Comp Engn, Av Albert Einstein 400, BR-13083852 Campinas, SP - Brazil

^[2] Univ Estadual Campinas, Sch Chem Engn, Ctr Innovat New Energies, Adv Energy Storage Div, Av Albert Einstein 500, BR-13083852 Campinas, SP - Brazil

^[3] Fed Univ Jequitinhonha E Mucuris Valley, Lab Fundamental & Appl Electrochem, Dept Chem, Rodovia MGT 367, Km 583, 5000 Alto Jacuba, BR-39100000 Diamantina, MG - Brazil

• Tipo de documento: Artigo Científico
• Fonte: SCIENTIFIC REPORTS; v. 10, n. 1 NOV 5 2020.
• Citações Web of Science: 0

Resumo

It is common to find in the literature different values for the working voltage window (WVW) range for aqueous-based supercapacitors. In many cases, even with the best intentions of the widening the operating voltage window, the measured current using the cyclic voltammetry (CV) technique includes a significant contribution from the irreversible Faradaic reactions involved in the water-splitting process, masked by fast scan rates. Sometimes even using low scan rates is hard to determine precisely the correct WVW of the aqueous-based electrochemical capacitor. In this sense, we discuss here the best practices to determine the WVW for capacitive current in an absence of water splitting using complementary techniques such as CV, chronoamperometry (CA), and the electrochemical impedance spectroscopy (EIS). To accomplish this end, we prepare and present a model system composed of multiwalled carbon nanotubes buckypaper electrodes housed in the symmetric coin cell and soaked with an aqueous-based electrolyte. The system electrochemical characteristics are carefully evaluated during the progressive enlargement of the cell voltage window. The presence of residual Faradaic current is verified in the transients from the CA study, as well as the impedance changes revealed by EIS as a function of the applied voltage, is discussed. We verify that an apparent voltage window of 2.0 V determined using the CV technique is drastically decreased to 1.2 V after a close inspection of the CA findings used to discriminate the presence of a parasitic Faradaic process. Some orientations are presented to instigate the establishment in the literature of some good scientific practices concerned with the reliable characterization of supercapacitors. (AU)

• Processo FAPESP: 18/20756-6 - Desenvolvimento de pseudocapacitores a partir de compósitos de óxidos metálicos e carvão ativado
• Beneficiário: Willian Gonçalves Nunes
• Modalidade de apoio: Bolsas no Brasil - Doutorado
• Processo FAPESP: 17/11958-1 - CINE - Divisão para Armazenamento de Energia Avançado
• Beneficiário: Rubens Maciel Filho
• Modalidade de apoio: Auxílio à Pesquisa - Programa Centros de Pesquisa em Engenharia
• Processo FAPESP: 14/02163-7 - Desenvolvimento de dispositivos supercapacitores a partir de grafenos, nanotubos de carbono e diamantes
• Beneficiário: Hudson Giovani Zanin
• Modalidade de apoio: Auxílio à Pesquisa - Jovens Pesquisadores