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Multiphase photocatalysts Cd1-xZnxS/TiO2 were synthesized through the deposition of solid solutions of cadmium and zinc sulfides on the surface of titania samples with different porous structures, including a 3D-ordered meso/macroporous structure. The photocatalysts were characterized by a wide range of experimental techniques: X-ray diffraction, high-resolution transmission electron microscopy combined with energy-dispersive X-ray spectroscopy, N2 adsorption at 77 K, X-ray photoelectron spectroscopy, and UV/VIS spectroscopy. The photocatalytic activity was tested in a batch reactor for the H2 evolution reaction from aqueous solutions of Na2S/Na2SO3 under visible-light irradiation (λ=450 nm). The highest achieved photocatalytic activity was 1.8 mmol H2 per gram of photocatalyst per hour. The regular porous structure of titania was demonstrated to enhance the photocatalytic activity and stability of Cd0.4Zn0.6S/TiO2 samples. [ABSTRACT FROM AUTHOR]

We explored the photoreforming of rice and corn starch with simultaneous hydrogen production over a Cd0.7Zn0.3S-based photocatalyst under visible light irradiation. The photocatalyst was characterized by UV–vis diffuse reflectance spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The influence of starch pretreatment conditions, such as hydrolysis temperature and alkaline concentration, on the reaction rate was studied. The maximum rate of H2 evolution was 730 μmol·h−1·g−1, with AQE = 1.8% at 450 nm, in the solution obtained after starch hydrolysis in 5 M NaOH at 70 °C. The composition of the aqueous phase of the suspension before and after the photocatalytic reaction was studied via high-performance liquid chromatography, and such products as glucose and sodium gluconate, acetate, formate, glycolate, and lactate were found after the photocatalytic reaction. [ABSTRACT FROM AUTHOR]

A series of solid solutions of cadmium and manganese sulfides, Cd1−xMnxS (x = 0–0.35), and composite photocatalysts, CdS-β-Mn3O4-MnOOH, were synthesized by precipitation with sodium sulfide from soluble cadmium and manganese salts with further hydrothermal treatment at 120 °C. The obtained photocatalysts were studied by the X-ray diffraction method (XRD), UV-vis diffuse reflectance spectroscopy, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and N2 low temperature adsorption. The photocatalysts were tested in hydrogen production using a Na2S/Na2SO3 aqueous solution under visible light (λ = 450 nm). It was shown for the first time that both kinds of photocatalysts possess high activity in hydrogen evolution under visible light. The solid solution Cd0.65Mn0.35S has an enhanced photocatalytic activity due to its valence and conduction band position tuning, whereas the CdS-β-Mn3O4-MnOOH (40–60 at% Mn) samples were active due to ternary heterojunction formation. Further, the composite CdS-β-Mn3O4-MnOOH photocatalyst had much higher stability in comparison to the Cd0.65Mn0.35S solid solution. The highest activity was 600 mmol g−1 h−1, and apparent quantum efficiency of 2.9% (λ = 450 nm) was possessed by the sample of CdS-β-Mn3O4-MnOOH (40 at% Mn). [ABSTRACT FROM AUTHOR]

The effect of transition alumina (γ‐, η‐, χ‐Al2O3) on the activity and stability of model chromia/alumina catalysts with 4 wt% Cr in isobutane dehydrogenation is studied. It is shown that a fresh catalyst with η‐Al2O3 as a support has the highest activity, while with χ‐Al2O3 has the lowest one. The characterization of the catalysts by N2 adsorption, X‐ray diffraction (XRD), electron spin resonance (ESR) spectroscopy, and X‐ray photoelectron spectroscopy (XPS) is used to describe changes in the catalysts induced by high‐temperature treatment at 800, 1000, and 1200 °C in air. It is shown that sintering of the alumina support and formation of chromia‐alumina solid solutions are the reasons of irreversible decline in the catalytic activity. Cr/γ‐Al2O3 is found to be the most stable to sintering and phase transformation, whereas Cr/χ‐Al2O3 is found to be the least stable. Due to its highest initial activity, the η‐Al2O3‐supported catalyst loses its dehydrogenation activity most rapidly as the calcination temperature is raised. The segregation of sodium impurities is observed in the course of heat treatment, which may be an additional cause of deactivation. [ABSTRACT FROM AUTHOR]

Graphitic carbon nitride (g-C 3 N 4) modified with bromine and iodine was synthesized by a novel two-stage technique that included hydrothermal pre-treatment of melamine and its calcination in a mixture with ammonium halide. Prepared photocatalysts were tested by a set of methods including X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), thermal gravimetric analysis (TGA), low temperature nitrogen adsorption, transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CVA), impedance spectroscopy, and the Mott – Schottky method. All the photocatalysts were studied in the photocatalytic hydrogen production from triethanolamine (TEOA) under visible light irradiation (λ = 428 nm). The most active photocatalyst was prepared from a mixture of 50% NH 4 I and 50% melamine. Its catalytic activity (2120 μmol g−1 h−1) was 35 times higher than that of the catalyst synthesized by the simple calcination of melamine. The highest short-circuit current density of 2.7 mA/cm2 was obtained with a sample synthesized from the mixture of 80% NH 4 Br and 20% melamine. [Display omitted] • Halide-modified g-C 3 N 4 was prepared by a novel two-stage technique. • High catalytic activity was assigned to changes in S BET and electronic structure. • I-doped samples were more active in H 2 production than Br-doped ones. • The highest catalytic activity was 2120 μmol Н 2 g−1 h−1. • Br-doped samples demonstrated higher J sc than I-doped samples. [ABSTRACT FROM AUTHOR]

Novel composite photocatalysts consisting of a cadmium and zinc sulfide solid solution (Cd 0.6 Zn 0.4 S) and zinc sulfide (ZnS) nanoparticles were successfully prepared by a simple hydrothermal treatment of suspended Cd 0.3 Zn 0.7 S at 120 °C. The as-obtained materials were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and UV-VIS diffuse reflection spectroscopy. The obtained photocatalysts were tested in the photocatalytic evolution of hydrogen from a Na 2 S/Na 2 SO 3 aqueous solution under visible light irradiation (λ = 450 nm). It is shown that the hydrothermal treatment of Cd 0.3 Zn 0.7 S at 120 °C increases the activity by a factor of 7.5 due to the phase transformations of the solid solution with the formation of the multiphase Cd 0.6 Zn 0.4 S/ZnS sample. The deposition of gold on the surface of Cd 0.6 Zn 0.4 S/ZnS leads to a further increase in activity: the achieved photocatalytic activity and quantum efficiency (450 nm) for 1%Au/Cd 0.6 Zn 0.4 S/ZnS are 17.4 mmol g−1 h−1 and 42.6%, respectively. This excellent performance is found to be attributable to the transformation of Cd 1-x Zn x S from the cubic to the hexagonal phase during the hydrothermal treatment. Additionally, photoelectrodes based on Cd 0.6 Zn 0.4 S/ZnS and FTO were synthesized and tested in a two-electrode cell. A high value of the photocurrent equal to 0.5 mA/cm2 is achieved for the Cd 0.6 Zn 0.4 S/ZnS/FTO electrode. An investigation by means of impedance spectroscopy reveals the longer lifetime of photogenerated charge carriers in the Cd 0.6 Zn 0.4 S/ZnS/FTO photoelectrode if to compare with Cd 0.3 Zn 0.7 S/FTO system. Image 1 • Au/Cd 0.6 Zn 0.4 S/ZnS photocatalysts were prepared via simple hydrothermal synthesis. • The highest value of the photocatalytic activity was 17.4 mmol H 2 per hour per gram. • The highest apparent quantum efficiency was 42.6% (450 nm). • Photocurrent 0.5 mA/cm2 was achieved for the Cd 0.6 Zn 0.4 S/ZnS/FTO electrode. [ABSTRACT FROM AUTHOR]