Electrosynthesis and Physicochemical Properties of PbO[sub 2] Films

Abstract

An electrochemical and X-ray diffraction study has been conducted on the formation of lead dioxide deposits on platinum, from nitric acid solutions, as a function of potential and temperature. It has been shown that these parameters strongly influence the morphology and electrocatalytic activity of the PbO 2 films. The electrodeposition process is satisfactorily described by an electrochemical, chemical, electrochemical mechanism: ͑i͒the second electron transfer stage and Pb 2ϩ diffusion control the dioxide formation in the lower and higher overpotential range, respectively. Temperature and potential ͑or current͒ are important parameters in the electrodeposition process. Depending on the potential region, the process can be kinetically or diffusion controlled. In an acid electrolyte, where mainly the ␤-PbO 2 modification is electrodeposited, the amount of ␣-phase impurity increases with increasing potential in the kinetically controlled region and decreases in the diffusion controlled domain. In addition, relatively low electrodeposition potentials and high temperatures favor an increase of the crystallite size with preferred crystallographic orientation for both ␣and ␤-PbO 2 modifications. The temperature of the growth solution affects the crystallinity of the resulting oxide deposits and has a marked effect on their performance as anodes in processes at high positive potentials such as ozone generation.

Electrodeposited lead dioxide coatings

“…8,[37][38][39][40][41][42] The sequence of chemical steps leading from Pb(II) in solution to solid lead dioxide has been the subject of much speculation. The most widely quoted mechanism is that proposed by Velichenco et al [43][44][45][46] involving adsorbed OH as a key intermediate:…”

Electrochemical Deposition of Lead Dioxide Nanostructured Thin Films

“…This reveals that the deposition rate clearly increases with increasing pH (toward neutral). In order to explain the influence of solution pH on PbO 2 deposition rate, the following reactions for electrochemical deposition are considered 28 .…”

Fatores que influenciam a formação da fase β-PbO2 em filmes eletrossintetizados galvanostaticamente sobre substrato de tecido de carbono

“…Entretanto, outros autores 16,17 chegaram a conclusões semelhantes às encontradas no presente estudo, ou seja, a diminuição do pH favorecendo a predominância da fase β-PbO 2 nos filmes eletrodepositados. Segundo Carr e Hampson, 16 a forma β é mais estável em meios ácidos já que nesse ambiente a forma α modifica espontaneamente sua estrutura para a forma β-PbO 2 .…”