Ga-Promoted Photocatalytic H2 Production over Pt/ZnO Nanostructures

Transition metal compounds: From properties, applications to wettability regulation

Transition metal compounds (TMCs) have the advantages of abundant reserves, low cost, non-toxic and pollution-free, and have attracted wide attention in recent years. With the development of two-dimensional layered materials, a new two-dimensional transition metal carbonitride (MXene) has attracted extensive attention due to its excellent physicochemical properties such as gas selectivity, photocatalytic properties, electromagnetic interference shielding and photothermal properties. They are widely used in gas sensors, oil/water separation, wastewater and waste-oil treatment, cancer treatment, seawater desalination, strain sensors, medical materials and some energy storage materials. In this view, we aim to emphatically summarize MXene with their properties, applications and their wettability regulation in different applications. In addition, the properties of transition metal oxides (TMOs) and other TMCs and their wettability regulation applications are also discussed.

Highly efficient nanostructured CoFe2 O4 thin film electrodes for electrochemical degradation of rhodamine B

In this work, we report the application of highly efficient electrodeposited cobalt ferrite (CoFe₂ O₄ ) thin films in electrochemical degradation of rhodamine B. XRD, FTIR and Raman spectroscopic studies confirmed the formation of single phase CoFe₂ O₄ . SEM analysis revealed a very fine nanorods dispersed uniformly with average size around 30 nm. UV-Vis spectrophotometry emphasized that the optical band gap value is 1.6 eV. Moreover, the elaborated CoFe₂ O₄ thin films showed a good efficiency for the electrochemical degradation of an aqueous solution of rhodamine B (RhB) attaining 99% during the first 3 min of reaction time. The trapping experiments revealed that the hydroxyl radicals were the main active species leading to the removal of RhB initial concentration of 10 mg/L in a very short time. PRACTITIONER POINTS: A simple electrodeposition technique was used to fabricate CoFe₂ O₄ thin. XRD and FTIR studies revealed the formation of pure cubic spinel phase. Nano-rod like morphology has been successfully synthesized. The rhodamine B aqueous solution has been completely decolorized using the obtained CoFe₂ O₄ thin films.

Tailoring the Dopant Distribution in ZnO:Mn Nanocrystals

The synthesis of semiconductor nanocrystals with controlled doping is highly challenging, as often a significant part of the doping ions are found segregated at nanocrystals surface, even forming secondary phases, rather than incorporated in the core. We have investigated the dopant distribution dynamics under slight changes in the preparation procedure of nanocrystalline ZnO doped with manganese in low concentration by electron paramagnetic resonance spectroscopy, paying attention to the formation of transient secondary phases and their transformation into doped ZnO. The acidification of the starting solution in the co-precipitation synthesis from nitrate precursors lead to the decrease of the Mn²⁺ ions concentration in the core of the ZnO nanocrystals and their accumulation in minority phases, until ~79% of the Mn²⁺ ions were localized in a thin disordered shell of zinc hydroxynitrate (ZHN). A lower synthesis temperature resulted in polycrystalline Mn-doped ZHN. Under isochronal annealing up to 250 °C the bulk ZHN and the minority phases from the ZnO samples decomposed into ZnO. The Mn²⁺ ions distribution in the annealed nanocrystals was significantly altered, varying from a uniform volume distribution to a preferential localization in the outer layers of the nanocrystals. Our results provide a synthesis strategy for tailoring the dopant distribution in ZnO nanocrystals for applications ranging from surface based to ones involving core properties.

Hydrogen production from methanol aqueous solution by ZnO/Zn(OH)2 macrostructure photocatalysts

Photocatalytic H₂ generation was studied for a series of ZnO/Zn(OH)₂ macrostructure photocatalysts. Different ZnO/Zn(OH)₂ macrostructures were prepared through a one-step hydrothermal method by adjusting the pH values of the solution and the concentration of dodecyl sulfate. Three different morphologies of the ZnO/Zn(OH)₂ macrostructure were synthesized and studied using SEM and XRD. The reflectance spectra revealed that the cone shaped ZnO/Zn(OH)₂ macrostructure (ZnO-C) had the lowest reflectivity of UV light. It was found that the photoelectronic properties depend on the morphology of the ZnO/Zn(OH)₂ macrostructures. The photocatalytic activity of these ZnO/Zn(OH)₂ macrostructure hybrids (about 0.070 mmol g⁻¹ h⁻¹) were higher than that observed for ZnO nanorods (0.050 mmol g⁻¹ h⁻¹). These results suggest the substantial potential of metal oxide materials with macrostructures in photocatalytic water splitting applications.

ZnO/Zn(OH)₂ macrostructure photocatalysts prepared using a one-step hydrothermal method demonstrated highly efficient photocatalytic hydrogen production.

Three-dimensionally ordered macroporous Sn4+-doped TiO2 with anatase–rutile mixed phase via Pt loading by photoreduction method: enhanced photodegradation and hydrogen production performance

3DOM Pt/Sn–TiO₂ with anatase–rutile mixed phase was successfully prepared by the colloidal crystal template method and the photoreduction method. A series of photocatalytic experiments showed that 3DOM Pt/Sn–TiO₂ exhibited significant photocatalytic activity in photodegradation and water splitting.

In situ doping of Pt active sites via Sn in double-shelled TiO2 hollow nanospheres with enhanced photocatalytic H2 production efficiency

A Sn⁴⁺-doped double-shelled Pt/TiO₂ hollow nanocatalyst (DHS-SnPt) with excellent photocatalytic H₂ production efficiency was prepared successfully via a facile hydrothermal method.