Enhancement of photoelectrochemical activity for water splitting by controlling hydrodynamic conditions on titanium anodization

Abstract

Tel.

Effect of Reynolds number and lithium cation insertion on titanium anodization

“…The electrical equivalent circuit proposed is shown in Figure 6d and it is formed by a resistive 10 element (R s ), corresponding to the electrolyte resistance, and two groups of resistances and constant phase elements (R-CPE), corresponding to the nanotubular layer (R 1 -CPE 1 ) and the compact TiO 2 layer (R 2 -CPE 2 ) [15,40]. This electrical equivalent circuit has been already used by other authors.…”

“…Thus, these defects improve the charge transfer along the nanotubes (this is in agreement with the results obtained by means of EIS, to be applied to the semiconductor to reduce the band bending to zero. Additionally, this electrochemical parameter is related to the potential drop at the depletion space charge layer (U SC ) and the applied external potential (U) [15], according to eq 4.…”

“…This is in agreement with the EIS and M-S measurements (lower R 1 values and higher N D for higher Re) and FE-SEM images. The high photocurrent densities obtained for the nanostructures anodized at higher Reynolds numbers are related to an increase in the conductivity of the NTs, due to a higher density of defects within their structure, which 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 14 favors the current flow [15,52]. These high photocurrent densities obtained for samples anodized under hydrodynamic conditions are also directly related to an increase in the active area of the nanotubes exposed to the electrolyte with increasing Re.…”

“…In order to achieve a high surface area and consequently, to enhance the photocatalytic activity, TiO 2 is synthesized in the form of nanotube arrays [15]. Nowadays, TiO 2 nanotubes are synthesized by several methods, including sol-gel transcription [16,17], hydrothermal processes [18,19] and anodization of titanium in fluoride-based electrolytes [20,21].…”

ZnO/ZnS heterostructures for hydrogen production by photoelectrochemical water splitting

“…This technique makes possible to grow the nanostructures directly on the metal substrate (back contact), so they can be used directly as photoanodes, thus avoiding compaction or sintering of nanoparticles on the metallic substrate. 16 Whether the correct electrolyte is selected, ZnO/ZnS heterostructures can be formed on zinc by electrochemical anodization. There is scarce literature that evaluates the photoelectrochemical behavior of ZnO/ZnS nanostructures obtained by anodization.…”