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The transformations of single-phase Pt/Cd 1− x Zn x S and multiphase Pt/Cd 1− x Zn x S/ZnO/Zn(OH) 2 and Pt/Cd 1− x Zn x S/Zn(OH) 2 during photocatalytic hydrogen evolution from aqueous solutions of ethanol under visible light ( λ = 450 nm) were investigated. Cyclic tests including long-term experiments were conducted for all photocatalysts. The photocatalysts were investigated before and after the photocatalytic reaction by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and UV–vis spectroscopy techniques. Activation during photocatalytic hydrogen evolution was observed for all multiphase photocatalysts, whereas single phase Pt/Cd 1− x Zn x S was shown to exhibit a strong deactivation. The activation is likely caused by the formation of the ϵ-Zn(OH) 2 phase in a basic medium. The highest exhibited rate of hydrogen evolution on the composite photocatalyst was 3400 μmol g −1 h −1 , and stability during ten 5-hour photocatalytic runs was observed. [ABSTRACT FROM AUTHOR]

In this work, new photocatalysts based on Cd1−xMnxS sulfide solid solutions were synthesized by varying the fraction of MnS (x = 0.4, 0.6, and 0.8) and the hydrothermal treatment temperature (T = 100, 120, 140, and 160 °C). The active samples were modified with Pt and NiS co-catalysts. Characterization was performed using various methods, including XRD, XPS, HR TEM, and UV-vis spectroscopy. The photocatalytic activity was tested in hydrogen evolution from aqueous solutions of Na2S/Na2SO3 and glucose under visible light (425 nm). When studying the process of hydrogen evolution using an equimolar mixture of Na2S/Na2SO3 as a sacrificial agent, the photocatalysts Cd0.5Mn0.5S/Mn(OH)2 (T = 120 °C) and Cd0.4Mn0.6S (T = 160 °C) demonstrated the highest activity among the non-modified solid solutions. The deposition of NiS co-catalyst led to a significant increase in activity. The best activity in the case of the modified samples was shown by 0.5 wt.% NiS/Cd0.5Mn0.5S (T = 120 °C) at the extraordinary level of 34.2 mmol g−1 h−1 (AQE 14.4%) for the Na2S/Na2SO3 solution and 4.6 mmol g−1 h−1 (AQE 2.9%) for the glucose solution. The nickel-containing samples possessed a high stability in solutions of both sodium sulfide/sulfite and glucose. Thus, nickel sulfide is considered an alternative to depositing precious metals, which is attractive from an economic point of view. It worth noting that the process of photocatalytic hydrogen evolution from sugar solutions by adding samples based on Cd1−xMnxS has not been studied before. [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]

Multiphase photocatalysts Pt/Cd 1− x Zn x S/ZnO/Zn(OH) 2 , Pt/Cd 1− x Zn x S/ZnO, and Pt/Cd 1− x Zn x S/Zn(OH) 2 were synthesized by a new two-step technique. 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, low-temperature N 2 adsorption/desorption, and UV/VIS spectroscopy. The photocatalytic activity was tested in a batch reactor in the reaction of H 2 evolution from aqueous solutions of ethanol under visible light irradiation ( λ > 420 nm). The highest achieved photocatalytic activity was 2256 μmol H 2 per gram of photocatalyst per hour; the highest quantum efficiency was 10.4%. The activity of Pt/Cd 1− x Zn x S/Zn(OH) 2 was higher than that of Pt/Cd 1− x Zn x S/ZnO/Zn(OH) 2 and Pt/Cd 1− x Zn x S/ZnO. The explanation of enhanced activity of zinc–cadmium sulfide/ε-zinc hydroxide based on quantum calculations was suggested. [ABSTRACT FROM AUTHOR]

Two types of nickel-modified Cd1−xZnxS-based photocatalysts, CdxZn1−xNiySy+1 (mol% Ni = 0.05–0.5; x = 0.8) and yNiS/CdxZn1−xS (mol% Ni = 0.1–1.0; x = 0.8), were prepared via a simple two-stage technique. The samples were characterized by XRD, UV–vis spectroscopy, and XPS techniques. The activity of the synthesized photocatalysts were tested in the gas-phase photocatalytic reduction of CO2 under visible light (λ = 450 nm). It has been shown that both CdxZn1−xNiySy+1 and yNiS/CdxZn1−xS samples with ultra-low content of nickel sulfide have improved activity in the carbon dioxide reduction in comparison to bare CdxZn1−xS solid solutions. Also, it has been demonstrated that the addition of the reducing agent—hydrogen—into the system does not lead to a positive effect: the rate of CO2 reduction either remains unchanged or decreases. [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]

[Display omitted] The optimal conditions for the synthesis of platinized graphitic carbon nitride (Pt/g-C 3 N 4) have been found. It was investigated as a catalyst for the production of hydrogen from aqueous solutions of triethanolamine (TEOA) under irradiation with visible light. The highest photocatalytic activity of 450 μmol h−1 g−1 and an apparent quantum efficiency of 1.1% were demonstrated by the 1% Pt/g-C 3 N 4 sample prepared from melamine by calcining at 600 °C for 2 h. [ABSTRACT FROM AUTHOR]

The promotion of the photocatalytic activity of the Cd 0.3 Zn 0.7 S nanoparticles via deposition of some copper species, such as Cu x S and Cu 0 , as a co-catalyst, in the hydrogen production under visible light irradiation from aqueous solutions of a sacrificial Na 2 S/Na 2 SO 3 system was studied. The state of the samples was characterized with a wide range of physical methods both in the initial state as well as after their photocatalytic operation. An evolution of both photocatalytic activity and the state of the photocatalyst particles was registered by a set of the physical methods. The highest apparent quantum efficiency and photocatalytic activity which were achieved at illumination by light with λ = 450 nm over the 0.1 wt% Cu x S/Cd 0.3 Zn 0.7 S sample for the photocatalytic hydrogen evolution from Na 2 S/Na 2 SO 3 aqueous solutions were 23.1% and 6.4 mmol g −1 h −1 , respectively. It was shown that the deposited Cu species undergo the transformation to Cu x S during the photocatalytic production of hydrogen, and these are the copper sulfide nanoparticles that increase the activity of the Cd 1-x Zn x S solid solutions. This statement agrees well with the principle of a constancy of the state of heterogeneous catalysts under their operation in the same reaction media established by G.K. Boreskov in the 1950s. [ABSTRACT FROM AUTHOR]

Two types of photocatalysts, 1%Pt/Cd1−xZnxS/g-C3N4 (x = 0.2–0.3) and Cd1−xZnxS/1%Pt/g-C3N4 (x = 0.2–0.3), were synthesized by varying the deposition order of platinum, and a solid solution of cadmium and zinc sulfides onto the surface of g-C3N4. The characterization of photocatalysts showed that, for 1%Pt/Cd1−xZnxS/g-C3N4, small platinum particles were deposited onto a solid solution of cadmium and zinc sulfides; in the case of Cd1−xZnxS/1%Pt/g-C3N4, enlarged platinum clusters were located on the surface of graphitic carbon nitride. Based on the structure of the photocatalysts, we assumed that, in the first case, type II heterojunctions and, in the latter case, S-scheme heterojunctions were realized. The activity of the synthesized samples was tested in hydrogen evolution from triethanolamine (TEOA) basic solution under visible light (λ = 450 nm). A remarkable increase in hydrogen evolution rate compared to single-phase platinized 1%Pt/Cd1−xZnxS photocatalysts was observed only in the case of ternary photocatalysts with platinum located on the g-C3N4 surface, Cd1−xZnxS/1%Pt/g-C3N4. Thus, we proved using kinetic experiments and characterization techniques that, for composite photocatalysts based on Cd1−xZnxS and g-C3N4, the formation of the S-scheme mechanism is more favorable than that for type II heterojunction. The highest activity, 2.5 mmol H2 g−1 h−1, with an apparent quantum efficiency equal to 6.0% at a wavelength of 450 nm was achieved by sample 20% Cd0.8Zn0.2S/1% Pt/g-C3N4. [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]