ElsevierFernández Domene, RM.; Sánchez Tovar, R.; Lucas-Granados, B.; Roselló-Márquez, G.; Garcia-Anton, J. (2017). A simple method to fabricate high-performance nanostructured WO3 photocatalysts with adjusted morphology in the presence of complexing agents. (J. .The rich and complex chemistry of tungsten was employed to synthesize innovative WO3 nanoplatelets/nanosheets by simple anodization in acidic electrolytes containing different concentrations of complexing agents or ligands, namely Fand H2O2. The morphological and photoelectrochemical properties of these nanostructures were characterized. The best of these nanostructures generated stable photocurrent densities of ca. 1.8 mA cm -2 at relatively low bias potentials (for WO3) of 0.7 VAg/AgCl under simulated solar irradiation, which can be attributed to a very high active surface area.This work demonstrates that the morphology and dimensions of these nanostructures, as well as their photoelectrochemical behavior, can be controlled by adjusting the ligand concentration in the electrolytes, hence providing an easy and non-expensive route to fabricate and customize high-performance nanostructured photocatalysts for clean energy production and environmental applications.

Improvement in photocatalytic activity of stable WO3 nanoplatelet globular clusters arranged in a tree-like fashion: Influence of rotation velocity during anodization. Applied Catalysis B:

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Iron oxide nanostructures are of particular interest because they can be used as photocatalysts in water splitting due to their advantageous properties. Electrochemical anodization is one of the best techniques to synthesize nanostructures directly on the metal substrate (direct back contact). In the present study, a novel methodology consisting of the anodization of iron under hydrodynamic conditions is carried out in order to obtain mainly hematite (α-Fe 2 O 3) nanostructures to be used as photocatalysts for photoelectrochemical water splitting applications. Different rotation speeds were studied with the aim of evaluating the obtained nanostructures and determining the most attractive operational conditions. The synthesized nanostructures were characterized by means of Raman spectroscopy, Field Emission Scanning Electron Microscopy, photoelectrochemical water splitting, stability against photocorrosion tests, Mott-Schottky analysis, Electrochemical Impedance Spectroscopy (EIS) and band gap 2 measurements. The results showed that the highest photocurrent densities for photoelectrochemical water splitting were achieved for the nanostructure synthesized at 1000 rpm which corresponds to a nanotubular structure reaching ~0.130 mA • cm-2 at 0.54 V (vs. Ag/AgCl). This is in agreement with the EIS measurements and Mott-Schottky analysis which showed the lowest resistances and the corresponding donor density values, respectively, for the nanostructure anodized at 1000 rpm.

A visible-light driven photoelectrochemical degradation process has been applied to a solution polluted with the organophosphate insecticide chlorfenvinphos. Different WO3 nanosheets/nanorods have been used as photoanodes. These nanostructured electrodes have been fabricated by anodization of tungsten and, subsequently, they have been subjected to a thermal treatment (annealing). The combined influence of annealing temperature (400º C and 600º C) and operation pH (1 and 3) on the photoelectrocatalytic behavior of these nanorods has been examined through a statistical analysis. Morphological, structural and photoelectrochemical characterizations have also been carried out. The chlorfenvinphos degradation efficiency depended both on annealing temperature and, specially, operation pH. At pH 1 and using an annealing temperature of 600º C, chlorfenvinphos has been effectively degraded following pseudo-first order kinetics with a coefficient of 7.8×10 -3 min -1 , and notably mineralized (more than 65% of Total Organic Carbon decrease).

ᵒC • min -1 achieving a photocurrent density of ~ 0.143 mA • cm -2 at 1.54 V (vs. RHE).The results indicate that the bi-layered nanostructure is an efficient photocatalyst for applications such as water splitting.

Iron oxide nanostructures are an attractive option for being used as photocatalyst in photoelectrochemical applications such as water splitting for hydrogen production. Nanostructures can be obtained by different techniques, and electrochemical anodization is one of the simplest methods which allows high control of the obtained morphology by controlling its different operational parameters. In the present study, the influence of the electrolyte temperature during electrochemical anodization under stagnant and hydrodynamic conditions was evaluated. Temperature considerably affected the morphology of the obtained nanostructures and their photoelectrochemical behavior. Several techniques were used in order to characterize the obtained nanostructures, such as Field Emission Scanning Electron Microscopy (before and after the annealing treatment in order to evaluate the changes in morphology), Raman spectroscopy, photocurrent vs. potential measurements and Mott-Schottky analysis. Results revealed that the nanostructures synthesized at an electrolyte temperature of 25 ⁰C and 1000 rpm are the most suitable for being used as photocatalysts for water splitting.

WO3 nanoplatelets have been synthesized by electrochemical anodization in acidic electrolytes containing two different complexing agents: fluorides and hydrogen peroxide. The influence of the morphology and size of these nanoplatelets on their photoelectrocatalytic performance has been studied following the degradation of a model organic recalcitrant compound, such as methyl orange (MO). The effect of several supporting electrolytes on this photodegradation process has also been checked.The best MO decoloration was observed for nanoplatelets fabricated in the presence of low H2O2 concentrations, whose distribution and small size made them expose a very high surface area to the problem solution. With this nanostructure, decoloration efficiencies of ca. 100% were obtained after just 60 min. This result is considerably better than others reported in similar works, indicating the excellent behavior of these WO3 nanoplatelets as photoelectrocatalysts.