Electrodeposition of porous zinc oxide electrodes in the presence of sodium laurylsulfate

Abstract

Thin porous films of crystalline ZnO have been prepared by cathodic electrodeposition from aqueous oxygen saturated zinc chloride solution in the presence of additives, such as different small organic acids (benzoic acid, p-toluenesulfonic acid, benzenetetracarboxylic acid) and a surfactant (sodium laurylsulfate). The small negatively charged additives influence the growth rate of ZnO due to the increase in the current density during electrodeposition with increasing number of functional groups. However, they do not change the morphology of the resulting ZnO films.The influence of sodium laurylsulfate on the growth rate of ZnO depends on its concentration. As long as the concentration is low there is only slight effect. However, if the provided concentration is high enough to achieve formation of micelles and to get assembly of these micelles on the charged electrode surface, the current density found during electrochemical deposition of ZnO was extremely high, indicating a strongly increased growth rate due to the catalysis by sodium laurylsulfate. The resulting films show remarkably different morphology, large surface area and good porosity. Sodium laurylsulfate incorporated in the ZnO films could be removed almost completely from the pores by extraction with ethanol without affecting the crystallinity of the material.