Comparison of Fe2TiO5/C photocatalysts synthesized via a nonhydrolytic sol-gel method and solid-state reaction method

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.

Influence of calcination temperature on photocatalytic H2O2productivity of hierarchical porous ZnO microspheres

Photocatalytic production of H₂O₂from water and atmospheric oxygen has been recognized as a green and sustainable chemical process, due to the abundance of raw materials and sustainable solar energy. Herein, flower-like hierarchical ZnO microspheres were prepared by hydrothermal method followed by calcination at different temperatures, and their photocatalytic performance in H₂O₂production was examined under simulated sunlight irradiation. The calcination temperature plays a vital role in the structure, morphology, and surface area of the final ZnO products as well as their optical and electrochemical properties, which are determining factors in their photocatalytic activity. The ZnO calcined at 300 °C (Zn-300) exhibits the highest activity and optimal stability, showing productivity of 2793μmol l^-1within 60 min of irradiation, which was 6.5 times higher than that of uncalcined ZnO precursor. The remarkable photocatalytic activity is attributed to enhanced light utilization, large surface area, abundant exposed active sites, improved separation efficiency, and prolonged carrier lifespan. Moreover, the results from cycling experiments indicate the as-prepared ZnO samples exhibit good stability and long-time performance. This work provides useful information for the preparation of hierarchical ZnO photocatalysts.