Cathodoluminescence characterization of Zno/Zns nanostructures anodized under hydrodynamic conditions

Abstract

ZnO/ZnS nanostructures were successfully synthesized by a simple electrochemical anodization of zinc in a glycerol based electrolyte containing sulfide-ammonium fluoride. The influence of different hydrodynamic conditions and anodization potentials during anodization on the morphological and electronic properties of the obtained ZnO/ZnS nanostructures was studied. The anodized samples were characterized using confocal Raman microscopy, X-Ray Diffraction (XRD), Field Emission Scanning Electronic Microscopy (FE-SEM), cathodoluminescence (CL), and photoelectrochemical water splitting tests under standard AM 1.5 conditions. The results showed that hydrodynamic conditions and higher potentials promoted the formation of ZnO/ZnS nanotubes with both higher sulphur content and crystalline defect density, which reduces the near band edge transition value of the materials and improves the photoelectrochemical activity for water splitting. Additionally, the higher photocurrent densities for water splitting were obtained for the samples anodized at the highest anodization potential and under hydrodynamic conditions, increasing in a 2 71% for the nanostructures anodized at 1000 rpm when the anodization potential changes from 20 to 40V.

Electrochemical synthesize and characterization of ZnO / ZnS nanostructures for hydrogen production

“…The high intensity of the planes is in order (101), (100) and (002) for hexagonal ZnO. On the other hand, the wurtzite ZnS contains (101), (112) and (104) crystalline plane which are in similar values of 2θ (degree) with hexagonal ZnO 46 . For this reason, crystalline planes of ZnS could not appear in the XRD pattern due to overlapping of 2θ values.…”

Anodization fabrication techniques and energy-related applications for nanostructured anodic films on transition metals

“…In glycerol-containing NaHCO 3 electrolytes, ZnO nanotubes, nanospheres and nanosponges were also formed in addition to nanowires [169] . Furthermore, hierarchically structured self-organized ZnO/ZnS nanotubes can be synthesized by the anodization of Zn in a Na 2 S-or (NH 4 ) 2 S-based electrolyte containing a small amount of NH 4 F [170][171][172] .…”

Formation of ZnO nanowires by anodization under hydrodynamic conditions for photoelectrochemical water splitting

“…5). This could explain the higher values in photocurrent response since a thinner diameter of the nanowires would increase the surface-to-volume ratio improving light absorption [19].…”

“…flower, snowflakes) structures [7]. Among them, one-dimensional nanostructures presents particular advantages as a photocatalyst [19] with a remarkably high surface-to-volume ratio [3,14,19] that increases the active area of light absorption and interaction with the electrolyte [19], and the quantum confinement effects in which the electrons only move along the axis of the one-dimensional nanostructures [1] and consequently, enhance electron transport efficiency [3,17,20].…”

“…In this context, electrochemical methods seem to be very promising as they are relatively low cost [2,3,6,11], fast [2,3,6] and allow large-scale synthesis [2,11]. Among them, anodization of Zn has been proposed as an efficient method for the rapid synthesis of ZnO nanowires [2,3] with the advantage of allowing the growth of the nanostructures directly on the metal substrate, which in turn would act as the back contact of the photoanode [9,19]. A problem with zinc oxide is that it presents instability in acidic electrolytes, which are generally used during anodization [5].…”