Prospects of Using Pseudobrookite as an Iron-Bearing Mineral for the Alkaline Electrolytic Production of Iron

The alkaline electrolytic production of iron is gaining interest due to the absence of CO₂ emissions and significantly lower electrical energy consumption when compared with traditional steelmaking. The possibility of using an iron-bearing pseudobrookite mineral, Fe₂TiO₅, is explored for the first time as an alternative feedstock for the electrochemical reduction process. To assess relevant impacts of the presence of titanium, similar electroreduction processes were also performed for Fe₂TiO₅·Fe₂O₃ and Fe₂O₃. The electroreduction was attempted using dense and porous ceramic cathodes. Potentiostatic studies at the cathodic potentials of −1.15–−1.30 V vs. an Hg|HgO|NaOH reference electrode and a galvanostatic approach at 1 A/cm² were used together with electroreduction from ceramic suspensions, obtained by grinding the porous ceramics. The complete electroreduction to Fe⁰ was only possible at high cathodic polarizations (−1.30 V), compromising the current efficiencies of the electrochemical process due to the hydrogen evolution reaction impact. Microstructural evolution and phase composition studies are discussed, providing trends on the role of titanium and corresponding electrochemical mechanisms. Although the obtained results suggest that pseudobrookite is not a feasible material to be used alone as feedstock for the electrolytic iron production, it can be considered with other iron oxide materials and/or ores to promote electroreduction.

Novel Fe2TiO5/reduced graphene oxide heterojunction photocatalyst with improved adsorption capacity and visible light photoactivity: experimental and DFT approach

The design of high-efficiency materials is a major challenge for the degradation of organic pollutants. In this work, type II p-n heterojunction photocatalyst Fe₂TiO₅/rGO, with enhanced performance, was successfully prepared through simple process. The Fe₂TiO₅/rGO composites were prepared by hosting several amounts of reduced graphene oxide (rGO) into pseudobrookite nanocrystals (Fe₂TiO₅) which were priorly synthesized by a solid-state reaction. The morphology and the properties of the as-prepared composites were characterized through different techniques. The fixation of rGO sheets on Fe₂TiO₅ was proved using the X-ray diffraction analysis (XRD). The results of the scanning electron microscope (SEM) analysis showed a good mixing of rGO with Fe₂TiO₅. The X-ray fluorescence (XRF) confirmed the purity of the pristine Fe₂TiO₅. The dynamic light scattering (DLS) illustrated a strong tendency to aggregation. Ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS) analysis was performed to characterize the electronic aspect as the gap and the Urbach energies. Finally, computational density functional theory (DFT) calculations were carried out to confirm the experimental results. The adsorptive and photoactivity of Fe₂TiO₅/rGO heterojunction photocatalysts were evaluated by methylene blue (MB) degradation under visible light irradiation. The highest MB degradation rate was achieved for Fe₂TiO₅/rGO_10% photocatalyst with the highest value of the elimination rate.

Electrochemical Oxidation of Metal-Catechol Complexes as a New Synthesis Route to the High-Quality Ternary Photoelectrodes: A Case Study of Fe2TiO5 Photoanodes

A new electrochemical, solution-based synthesis method to prepare uniform multinary oxide photoelectrodes was developed. This method involves solubilizing multiple metal ions as metal-catechol complexes in a pH condition where they are otherwise insoluble. When some of the catechol ligands are electrochemically oxidized, the remaining metal complexes become insoluble and are deposited as metal-catechol films on the working electrode. The resulting films are then annealed to form crystalline multinary oxide electrodes. Because catechol can serve as a complexing agent for a variety of metal ions, the newly developed method can be used to prepare a variety of multinary oxide films. In the present study, we used this method to prepare n-type Fe₂TiO₅ photoanodes and investigated their photoelectrochemical properties for use in a photoelectrochemical water-splitting cell. We also performed a computational investigation with two goals. The first goal was to investigate small electron polaron formation in Fe₂TiO₅. Charge transport in most oxide photoelectrodes involves small polaron hopping, but small polaron formation in Fe₂TiO₅ has not been examined prior to this work. The second goal was to investigate the effect of substitutional Sn doping at the Fe site on the electronic band structure and the carrier concentration of Fe₂TiO₅. The combined experimental and theoretical results presented in this study greatly improve our understanding of Fe₂TiO₅ for use as a photoanode.

Fe2TiO5 as an Efficient Co-catalyst To Improve the Photoelectrochemical Water Splitting Performance of BiVO4

Fe₂TiO₅ was synthesized via the solvothermal method and adopted as co-catalyst to improve the photoelectrochemical (PEC) water splitting performance of BiVO₄ photoanode. After surface modification by Fe₂TiO₅, the BiVO₄/Fe₂TiO₅ photoanode shows a 300 mV cathodic shift in onset potential and 3 times enhancement in photocurrent, which delivers a photocurrent density of 3.2 mA/cm² at 1.23 V vs reverse hydrogen electrode. Systematic optical, electrochemical, and intensity-modulated photocurrent spectroscopy characterizations were performed to explore the role of Fe₂TiO₅ and reveal that the enhanced PEC performance is mainly caused by the surface passivation effect of Fe₂TiO₅.