Lithium Ion Electro-Insertion and Spectroelectrochemical Properties of Films from Hexaniobate

Autor(es)

Rezende, Alex R. ^[1] ; Bizeto, Marcos A. ^[2] ; Constantino, Vera R. L. ^[3] ; Huguenin, Fritz ^[1]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Dept Quim, Fac Filosofia Ciencias & Letras Ribeirao Pret, BR-14040901 Ribeirao Preto, SP - Brazil

^[2] Univ Fed Sao Paulo, Dept Ciencias Exatas & Terra, BR-09972270 Diadema, SP - Brazil

^[3] Univ Sao Paulo, Dept Quim Fundamental, Inst Quim, BR-05513970 Sao Paulo - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Journal of Physical Chemistry C; v. 113, n. 25, p. 10868-10876, JUN 25 2009.
• Citações Web of Science: 8

Resumo

Layer-by-layer (LbL) films from K(2)Nb(6)O(17)(2-) and polyallylamine (PAH) and dip-coating films of H(2)K(2)Nb(6)O(17) were prepared on a fluorine-doped tin-oxide (FTO)-coated glass. The atomic force microscopy (AFM) images were carried out for morphological characterization of both materials. The real surface area and the roughness factor were determined on the basis of pseudocapacitive processes involved in the electroreduction/electrooxidation of gold layers deposited on these films. Next, lithium ion insertion into these materials was examined by means of electrochemical and spectroelectrochemical measurements. More specifically, cyclic voltammetry and current pulses under visible light beams were used to investigate mass transport and chromogenic properties. The lithium ion diffusion coefficient (D(Li)) within the LbL matrix is significantly higher than that within the dip-coating film, ensuring high storage capacity of lithium ions in the self-assembled electrode. Contrary to the LbL film, the potentiodynamic profile of absorbance change (Delta A) as a function of time is not similar to that obtained in the case of current density for the dip-coating film. Aiming at analyzing the rate of the coloration front associated with lithium ion diffusion, a spectroelectrochemical method based on the galvanostatic intermittent titration technique (GITT) was employed so as to determine the ``optical{''} diffusion coefficient (D(op)). In the dip-coating film, the method employed here revealed that the lithium ion rate is higher in diffusion pathways formed from K(2)Nb(6)O(17)(2-) sites that contribute more significantly to Delta A. Meanwhile, the presence of PAH contributed to the increased ionic mobility in diffusion pathways in the LbL film, with low contribution to the electrochromic efficiency. These results aided a better understanding of the potentiodynamic profile of the temporal change of absorbance and current density during the insertion/deinsertion of lithium ions into the electrochromic materials. (AU)

• Processo FAPESP: 05/60596-8 - Espécies complexas com potencial aplicação em bioinorgânica, catálise, farmacologia e química ambiental: concepção, preparação, caracterização e reatividade
• Beneficiário: Ana Maria da Costa Ferreira
• Modalidade de apoio: Auxílio à Pesquisa - Temático
• Processo FAPESP: 05/00106-7 - Materiais eletroativos automontados
• Beneficiário: Fritz Cavalcante Huguenin
• Modalidade de apoio: Auxílio à Pesquisa - Regular