DOI: 10.5281/zenodo.18674605
title: Synthesis and Characterisation of TiO2/ZnO2 hybrid nanostructures formed by electrodeposition with different Zn(NO3)2 concentrations and used in photoelectrochemical applications [Dataset]

description: The dataset contains the data that have been obtained during the synthesis and the characterization (structural, compositional, and electrochemical) of TiO2/ZnO2 hybrid nanostructures used in photoelectrochemical applications. TiO2/ZnO hybrid nanostructures were synthetized by electrochemical anodization of titanium to form TiO2 nanosponges with crystalline structure and subsequently ZnO electrodeposition. Different Zn(NO3)2 concentrations were used for electrodeposition (10–60 mM). A structural and compositional characterisation was performed using X-Ray Diffraction (XRD). Electrochemical characterisation of nanostructures was performed by Photoelectrochemical Water Splitting (PWS), stability to photocorrosion, Electrochemical Impedance Spectroscopy (EIS), and Mott-Schottky tests.

- Synthesis of TiO2/ZnO hybrid nanostructures:

The formation of TiO2/ZnO hybrid nanostructures was carried out by ZnO electrodeposition on crystalline TiO2 nanosponges. First, TiO2 nanosponges were synthesised by electrochemical anodization of titanium (Ti)under hydrodynamic conditions at room temperature. For this purpose, metallic titanium rod (99.3% purity and 8 mm in diameter) was polished with 240–4000 silicon carbide (SiC) papers to obtain a mirror surface.After that, the sample was sonicated in ethanol for 2 min, rinsed with distilled water, and dried with air. Finally, the sample was covered with a polytetrafluoroethylene (PTFE) coating (0.5 cm2 area exposed tothe electrolyte). Polished Ti was used as working electrode, and a platinum foil as counter electrode. A solution composed of glycerol/water (60/40 vol%) with 0.27 M ammonium fluoride (NH4F) at room temperaturewas used as electrolyte. The potential was increased from 0 to 30 V at a constant rate of 0.1 V·s-1 applying subsequently 30 V for 3 h. TiO2 nanosponges were then annealed at 450 ◦C for 1 h to obtain the anatasecrystalline structure of TiO2. Finally, the ZnO electrodeposition was carried out at a potential of -0.86 VAg/AgCl for 15 min at 75 ◦C with zinc nitrate hexahydrate (Zn(NO3)2⋅6H2O) concentrations between 10 and 60 mM. TiO2 nanosponges were used as working electrodes, a platinum tip was used as counter electrode, and an Ag/AgCl (3 M KCl) electrode was used as reference electrode.

- Structural and compositional characterisation of the nanostructures:

X-Ray Diffraction (XRD) was used to verify the ZnO formation, to identify the composition of the phases of the crystals, and to obtain the crystallite size of the nanostructures. In order to carry out this process, a Bruker D8AVANCE diffractometer with Cu radiation operating at 30 mA and 40 Kv was used.

- Electrochemical characterisation of the nanostructures:

The electrochemical characterisation was carried out in both dark and illuminated (AM 1.5, 100 mW·cm-2) conditions in a cell composed of three electrodes connected to a potentiostat (Autolab PGSTAT302 N)where the nanostructures were the working electrodes, a platinum tip was the counter electrode, and an Ag/AgCl (3 M KCl) electrode was the reference electrode. A 0.1 M NaOH aqueous solution was used aselectrolyte.

The photoelectrochemical response of nanostructures was measured by photoelectrochemical water splitting (PWS) tests performed between -1.0 and 0.84 VAg/AgCl with a scan rate of 2 mV·s-1 by chopped lightirradiation. In addition, stability tests to photocorrosion were also carried out applying a potential of 0.84 VAg/AgCl for 1 h. Electrochemical Impedance Spectroscopy (EIS) and Mott-Schottky (M-S) tests wereperformed to analyse the electrochemical behaviour of the nanostructures that presented the best photoelectrocatalytic performance. On the one hand, EIS was carried out at 0.6 VAg/AgCl in a frequency rangefrom 100 kHz to 10 mHz with a 10 mV signal amplitude. On the other hand, Mott-Schottky (M-S) tests were performed from 0.8 to -0.9 VAg/AgCl at a frequency of 10 kHz with an amplitude signal of 10 mV.