Estudos de Eletrodeposição dos metais do grupo do ferro em meio aquoso e solventes eutéticos profundos
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Data
2018-04-06
Autores
Sakita, Alan Massayuki Perdizio [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
Esta tese doutoral compreende o estudo do comportamento eletroquímico de íons metálicos do grupo do ferro para fins de eletrodeposição em solvente eutético profundo (SEP) e em meio aquoso. Para tal, o trabalho foi dividido em 5 capítulos, sendo os capítulos de 1 a 3 abordando estudos de eletroquímica e eletrodeposição em SEP e os capítulos 4 e 5 sobre a deposição em meio aquoso. O capitulo 1 mostra o comportamento eletroquímico do par redox Fe3+/Fe2+ no solvente eutético gliceline (cloreto de colina:glicerol na proporção 1:2), onde foi observada que a alta viscosidade do solvente torna a condutividade da solução bastante limitada. Assim, para estudo e obtenção dos parâmetros cinéticos por voltametria cíclica é necessária a aplicação de correções da queda ôhmica do meio. A analise semi-integrativa dos voltamogramas obtidos em SEP foi aplicada neste trabalho e demonstrou ser bastante simples e conveniente para a determinação de D, k0 e alfa aplicando correções post factum da queda ôhmica. Os capítulos 2 e 3 abordam a eletrodeposição de cobalto em SEP, onde foi realizada utilizando sais anidro e hidratado do metal. Em ambos os sais de cobalto avaliados foi possível depositar óxidos e hidróxidos do metal por aplicação de corrente catódica. O mecanismo de nucleação e crescimento demonstrou ser majoritariamente progressivo na ampla faixa de potencial estudado e a polimerização de glicerol na deposição utilizando sais hidratados foi observada através de FTIR, RMN e MEV. Para a formação de polímero é sugerida a polimerização radicalar mediada por Co(II), como forma de explicar a formação de espécies de Co(III) na estrutura do oxido caracterizada. Nos capítulos 4 e 5 foram estudados banhos de cloreto em meio aquoso para deposição CoFe e NiFe, que revelou a formação de multicamadas tipo metal|hidróxidos. Tais multicamadas exibem uma subcamada nanoparticulada de metal recoberta por hidróxidos lamelares duplos. Os depósitos em multicamadas obtidos em curto período de tempo (<5 s) demonstraram ser catalíticos para a reação de desprendimento de oxigênio em meio alcalino.
This doctoral thesis comprises the study on the electrochemical behavior of iron group metal ions devoted to their electrodeposition process in aqueous medium and in deep eutectic solvents (DESs). The thesis is divided into 5 chapters, being the chapter 1 to 3 dedicated to electrochemical and electrodeposition studies in DESs and the chapter 4 and 5 are related to the electrodeposition in aqueous medium. The chapter 1 describes the electrochemical behavior of the Fe2+/Fe3+ redox pair in glyceline (choline chloride:glycerol with 1:2 ratio) DES where is observed that the high viscosity of the solvent turns the solution conductivity very limited. Thus, in order to study and obtain the kinetic parameters by cyclic voltammetry is need the ohmic drop correction of the medium. The semiintegrative analysis of the obtained voltammograms in DES has been applied and demonstrated to be very simple and convenient for the determination of D, k0 and alpha by applying post factum correction of the ohmic drop. The chapters 2 and 3 comprise the cobalt electrodeposition in DES medium where it has been done by utilizing anhydrous and hydrated salts of the metal. In both cobalt salts evaluated herein, it has been possible to deposit metal oxides and hydroxides by application of cathodic current. The nucleation and growth mechanism has been demonstrated to be mainly progressive in the wide range of potential and the glycerol polymerization in the deposition, by using hydrated salts, has been observed by FTIR, NMR and SEM. For the polymer formation is suggested the radical polymerization mediated by Co(II) as a manner of explaining the formation of Co(III) species in the characterized oxide structure. Chapter 4 and 5 deals with chloride baths in aqueous medium for deposition of CoFe and NiFe where is observed the multilayer formation such as metal/hydroxides. Such multilayers exhibit a nanoparticulated sublayer of metal recovered by lamellar double hydroxides. The deposits in multilayers obtained at short periods of time (<5 s) reveal to be catalysts for oxygen evolution reaction in alkaline medium.
This doctoral thesis comprises the study on the electrochemical behavior of iron group metal ions devoted to their electrodeposition process in aqueous medium and in deep eutectic solvents (DESs). The thesis is divided into 5 chapters, being the chapter 1 to 3 dedicated to electrochemical and electrodeposition studies in DESs and the chapter 4 and 5 are related to the electrodeposition in aqueous medium. The chapter 1 describes the electrochemical behavior of the Fe2+/Fe3+ redox pair in glyceline (choline chloride:glycerol with 1:2 ratio) DES where is observed that the high viscosity of the solvent turns the solution conductivity very limited. Thus, in order to study and obtain the kinetic parameters by cyclic voltammetry is need the ohmic drop correction of the medium. The semiintegrative analysis of the obtained voltammograms in DES has been applied and demonstrated to be very simple and convenient for the determination of D, k0 and alpha by applying post factum correction of the ohmic drop. The chapters 2 and 3 comprise the cobalt electrodeposition in DES medium where it has been done by utilizing anhydrous and hydrated salts of the metal. In both cobalt salts evaluated herein, it has been possible to deposit metal oxides and hydroxides by application of cathodic current. The nucleation and growth mechanism has been demonstrated to be mainly progressive in the wide range of potential and the glycerol polymerization in the deposition, by using hydrated salts, has been observed by FTIR, NMR and SEM. For the polymer formation is suggested the radical polymerization mediated by Co(II) as a manner of explaining the formation of Co(III) species in the characterized oxide structure. Chapter 4 and 5 deals with chloride baths in aqueous medium for deposition of CoFe and NiFe where is observed the multilayer formation such as metal/hydroxides. Such multilayers exhibit a nanoparticulated sublayer of metal recovered by lamellar double hydroxides. The deposits in multilayers obtained at short periods of time (<5 s) reveal to be catalysts for oxygen evolution reaction in alkaline medium.
Descrição
Palavras-chave
Eletrodeposição, Eletroquímica, Voltametria, Íons metálicos, Solventes eutéticos profundos