Control on the morphology and photoelectrocatalytic properties of ZnO [Dataset]

Zinc oxide nanostructured electrodes were successfully synthesized by a simple method of anodization in different aqueous bicarbonate electrolytes. The influence of the anodization electrolyte composition (by adding ethanol or glycerol) on the morphology and the photoelectrocatalytic properties of the zinc oxide electrodes was studied, as well as the combined effect of anodizing under controlled hydrodynamic conditions. Field Emission Scanning Electron Microscope (FE-SEM) images of the ZnO electrodes showed that the addition of ethanol or glycerol to the anodization electrolyte resulted in changes in size and morphology of the nanostructures. Thus, ZnO nanowires, nanotubes, nanosponge and nanospheres were obtained. Additionally, multi-factor analysis of the variance (ANOVA) revealed that photocurrent density response during water splitting test experimented significant variations depending on the anodization electrolyte composition. In particular, the best photoelectrochemical performance was achieved for the ZnO nanostructures anodized in low amounts of ethanol or glycerol. Description of methods used for collection/generation of data: Anodization was performed using a zinc rod (99,999% purity/ 8 mm in diameter) as the working electrode and a platinum foil (1 cm2) as the counter electrode. Previously to anodization, the surface of the zinc rod was abraded with 240–4000 SiC paper to obtain a mirror finish, degreased by sonication in ethanol and dried in air. Subsequently, the zinc rod was covered by Teflon to exclusively expose 0.5 cm2 to the electrolyte. Then, anodization was performed at 10 V for 10 min in a 50 mM NaHCO3 aqueous electrolyte with different ethanol or glycerol amounts (10, 25 and 50% v/v). Conductivity of the fresh electrolytes was measured prior to anodization using a conductimeter (CRISON BASIC 30). Furthermore, anodization was performed both under stagnant and under controlled hydrodynamic conditions (5000 rpm) for each electrolyte composition using a rotating disk electrode (RDE). Current density was continuously registered during anodization. Finally, anodized samples were annealed in a tubular furnace (Carbolite TVS 12/600) for 1 h at 300 °C in an air atmosphere with a heating rate of 15 °C/min. The morphology of the samples was examined by means of Field Emission Scanning Electron Microscopy (FE-SEM). The length of the nanostructures was measured from cross section FESEM images by using an analysis FESEM software. In order to evaluate whether the anodization conditions produce significant variations in the photocurrent density response of the ZnO nanostructures during water splitting measurements a statistical analysis was performed with the software Statgraphics Centurion using a Multi-Factor Categorical design. The photocurrent density response (photocurrent density under light irradiation minus current density in the dark) of the water splitting test at −0.46 VAg/AgCl was the response variable, while two anodization factors were studied: organic solvent amount with 3 levels (10, 25 and 50% v/v) and RDE rotation speed with two levels (0 rpm and 5000 rpm). Methods for processing the data: Processed data are registered in files with extension csv.