Comparative Study of the Photocatalytic Hydrogen Evolution over Cd1−xMnxS and CdS-β-Mn3O4-MnOOH Photocatalysts under Visible Light (original) (raw)
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Russian Chemical Bulletin, 2017
Nanocrystals (NCs) of CdS with oleate surface (NC 1) and octadecyl thiolate surface (NC 2), stabilized by a polycation shell, were doped with nickel bis(2 aminobenzenethiolate) (1), cobalt(III) chlorobis(dimethylglyoximato)(2 mercaptopyridine) (2), and also with 1,2 ethanedithiol and didodecylsulfide clathrochelates of cobalt(II) (3 and 4). The influence of doping on the photocatalytic activity in the hydrogen evolution reaction was investigated. Complex 1 appeared to be the most effective cocatalyst for H 2 evolution with the reaction rate increased by the factor of 8-11. Accomodating the complex in a polymer shell yields the best result. The rate of H 2 evolution increases monotonically with increasing concentration of this complex until the concentration achieves the ratio of one complex molecule per single NC. It is shown that the chemical composition of the surface has a significant influence on their photocatalytic activity in the hydrogen evolution reaction. The activity of NC 2 is 200 times that of NC 1. The replacement of oleate groups of the latter with sulfide increases the activity of these photocatalysts by a factor of 2000.
International Journal of Hydrogen Energy, 2018
Cd (1-x) Zn x S hexagonal crystals were for the first time synthesized via thermal sulfurization of Cd (1-x) Zn x O particles by using the elemental sulfur as the sulfur source. A temperature profile in the tube furnace was designed to obtain the proposed particle size, crystal structure, and morphology. Synthesized Cd (1-x) Zn x S particles were characterized with scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy, and diffuse reflectance UVeVis spectroscopy. It was seen that there was a polynomial relationship between the band gap and Cd: Zn ratio in the Cd (1-x) Zn x S. Cd 0.58 Zn 0.23 S has shapeless particles between 250 and 500 nm particle size. It was observed that particle size decreased as Zn ratio increased in the Cd (1-x) Zn x S. Cd (1-x) Zn x S hexagonal crystals had nanostep surfaces which were one of the desired factors for achieving high photocatalytic efficiency. Finally, Synthesized Cd (1-x) Zn x S particles were used as photocatalysts for the photocatalytic hydrogen evolution reaction (HER). Cd 0.77 Zn 0.23 S structure behaved the most active one among the different compositions of Cd (1-x) Zn x S nanoparticles. Cd 0.77 Zn 0.23 S showed almost high photocatalytic activity for HER with 1927 mmol g À1 h À1 hydrogen evolution rate without using noble co-catalyst such as platinum. This good photocatalytic activity was believed to be due to the nanostep surface structure Cd 0.77 Zn 0.23 S which led the separation of the reduction and oxidation reaction sites and inhibited the recombination of the generated electrons and holes. Observation of considerably high photocurrent and open circuit potentials and changes in the electrochemical impedance spectroscopy responses supported the photocatalytic activity of the Cd 0.77 Zn 0.23 S particles.
Photocatalytic production of hydrogen in systems based on Cd x Zn1–x S/Ni0 nanostructures
Theoretical and Experimental Chemistry, 2009
A relation was established between the composition of Cd x Zn 1-x S nanoparticles and their ability to accumulate excess negative charge during irradiation. The rate of expenditure of the accumulated charge depends on the composition of the nanoparticles and is determined by their electric capacitance. A correlation was found between the photocatalytic activity of the Cd x Zn 1-x S nanoparticles in the release of hydrogen from solutions of Na 2 SO 3 , their composition, and their capacity for photoinduced accumulation of excess charge. It was shown that Ni 0 nanoparticles photodeposited on the surface of Cd x Zn 1-x S are effective cocatalysts for the release of hydrogen. It was found that Zn II
Catalysts, 2021
Photocatalytic H2 production utilizing H2S, an industrial side-product, is regarded as an environmentally friendly process to produce clean energy through direct solar energy conversion. For this purpose, sulfide-based materials, such as photocatalysts, have been widely used due to their good solar response and high photocatalytic activity. In this work, a ZnS–CdS composite was studied, and special attention was dedicated to the influence of the preparation parameters on its H2 production activity. The ZnS–CdS composite, with an enhanced photoactivity for H2 production, was synthesized both from ammine complexes and, in a conventional way, directly from acetates at various pH values. Deviating from the traditional method, the photoactivity of ZnS–CdS prepared from ammine complexes was not affected by the pH. Besides, the hydrothermal treatment and the ammonia content strongly influenced the rate of H2 production in this system. DRS, TEM, SEM, XRD, and quantum yield measurements prov...
The Journal of Physical Chemistry C, 2007
We describe a simple cadmium-thiourea complex thermolysis route for the formation of CdS nanocrystals with controlled dispersity, crystalline phase, composition, average grain size, and band gap. Visible-lightdriven photocatalytic activities for hydrogen production over the different CdS products have been compared. Phase structure and composition of the obtained CdS nanocrystals has been optimized either by changing the ratio of thiourea to Cd or by changing the annealing temperature. Over a broad annealing temperature range of 150-500°C, either cubic, a mixture of cubic and hexagonal, or hexagonal CdS nanocrystals are obtained at thiourea/Cd molar ratios of <1.0, 1.5-2.5, and 3.0-4.5, respectively. Nanocrystalline cubic CdS is stable at temperatures as high as 500°C for 0.5 h, and is converted to hexagonal CdS for annealing time longer than 1 h. The phase transition from cubic to hexagonal CdS occurs at temperatures of 200-300°C, and pure hexagonal CdS is formed at annealing temperatures higher than 600°C. The dispersity, crystallinity, and average grain size of the CdS nanocrystals has been determined as a function of annealing temperature and time. Increased photocatalytic activity is observed from the mixture of cubic and hexagonal CdS as compared to pure cubic or hexagonal CdS. Nearly monodisperse hexagonal CdS with good crystallinity and very fine particle size is expected to offer the highest photocatalytic activity for hydrogen production under visible light.
Separation and Purification Technology, 2013
Cadmium sulphide (CdS) nanostructures were synthesized via a simple chemical precipitation method by using Mercaptoethylamine hydrochloride (MEA) as a capping agent. Fine tuning of the nanosized CdS material was carried out by controlling the amount of the capping agent. The synthesized CdS nanostructures were characterized by UV-Vis spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), and UV-Vis diffuse reflectance spectroscopy (DRS). Optical absorption spectroscopy was mainly used to measure the band gap and size of the CdS nanostructures. The photocatalytic activities of the synthesized samples were investigated for degradation of methylene blue (MB) under blue LED (3 W) and solar light irradiation.
New Journal of Chemistry, 2014
In this work, we have synthesized CdS quantum dots and also supported CdS nanoparticles on ZSM-5 type metalosilicates (ferrisilicate and aluminosilicate) as CdS-metalosilicate composites. The photocatalytic activity for hydrogen production over the prepared catalysts was investigated. It can be observed that the synthesis of CdS quantum dots by a solvothermal method results in the enhancement of photocatalytic activity of this semiconductor in comparison to other procedures, which has been reported previously. Our objective was to improve the photocatalytic activity of our synthesized CdS nanoparticles; for this purpose, we have supported CdS on metalosilicates and investigated their photocatalytic activity. These composites show high efficiency for hydrogen production under visible light irradiation. This suggests that, due to the high surface area of metalosilicates, the effective and homogenous dispersion of CdS particles on the external surface or within the pores of metalosilicate can be achieved by supporting the nano-particles which inhibits the agglomeration of the formed semiconductor. We have thus distinguished that supporting of CdS nanoparticles leads to improvement of the photocatalytic activity in water reduction; so that the hydrogen production rate for CdS-metalosilicate composite was about 11 mmol h À1 g cat À1 ; which is significantly higher than that of unsupported CdS nanoparticles.
Journal of Physics and Chemistry of Solids, 2018
A simple, facile and organic-free hydrothermal method was utilized to synthesize cadmium sulfide (CdS) superstructures. The cadmium chloride and thiourea used as a Cd 2þ and S 2À ion sources for the growth of CdS superstructures. The reaction was carried out at different time and temperatures. The X-ray diffraction studies confirmed that the obtained products were highly crystalline with hexagonal phase. Scanning and transmission electron microscopy images reveal a monodisperse dendrite-like CdS superstructure. It consisted of a central long trunk with secondary branches, lying parallel to each other and making a certain angle with the central trunk, and small ternary branches grew out of the secondary branches. The selected area electron diffraction altogether with high-resolution electron microscopy patterns depicted that the leaves of dendrite were single crystalline in nature and preferentially grown along (111) direction. The UV-vis absorbance and photoluminescence study illustrated that the hierarchically grown CdS superstructures revealed the good quality of optical properties. A probable growth mechanism for the formation of CdS dendritic superstructures was also discussed and demonstrated by experimental results. The photocatalytic activity of CdS superstructures was studied with the photodegradation of methylene blue (MB) in an aqueous solution, under the visible light irradiation. The results showed that the degradation ratio of MB could reach 94.93% in 220 min. Based on the results, the possible mechanism of the photocatalytic reaction of MB with CdS dendrites is useful for visible light photocatalytic applications.
Catalysis Today, 2019
Photocatalytic production of hydrogen has been investigated over irradiated aqueous dispersions of mixed Cd-Zn sulfide catalysts (CZS) promoted with nickel or nickel phosphide in the presence of sulfide/sulfite ions as sacrificial electron donors. The CZS composites were prepared by a co-precipitation method followed by calcination in air at temperatures in the range of 300 to 600 o C. It has been found that heat treatment at 500 o C results in materials with increased activity for H2 evolution, which is attributed to the formation of the Zn0.78Cd0.22S phase. Photocatalytic performance of CZS(500) is further improved following addition of small amounts of Ni or Ni2P on the photocatalyst surface. The activity of the optimized materials, loaded with 0.05 wt.% Ni or 0.25 wt.% Ni2P, exhibit similar activity with a Pt-promoted CZS(500) catalyst, and is one order of magnitude higher than that of the reference TiO2 catalyst of the same platinum loading (0.25 wt.% Pt). Results of long-term stability tests show that the 0.25%Ni2P/CZS(500) catalyst is very stable in the presence of S 2-/SO3 2ions in solution, with cadmium leaching not exceeding 0.1% after 65 h under irradiation. Experiments performed with the use of low (or negative) cost waste materials, such as real wastewater resulting from film printing processes or glycerol solutions, demonstrate that the 0.25%Ni2P/CZS(500) photocatalyst exhibits stable H2 evolution even in the absence of S 2-/SO3 2ions and has the potential to be used as a solar light-responsive photocatalyst for practical applications.
International Journal of Hydrogen Energy, 2010
Visible light H 2 a b s t r a c t A series of Cd 1Àx Zn x S solid solutions were synthesized at 80 C with the assistance of sodium dodecylsulfate. The structures, optical properties and morphologies of the solid solutions have been studied by X-ray diffraction, UV-vis diffuse reflectance spectroscopy, and transmission electron microscopy. The photocatalytic H 2 evolution over the solid solutions under visible-light irradiation was investigated and the highest rate reached 2640 mmol h À1 g À1 even without any co-catalysts. The solid solution with optimum performance exhibited cubic structure rather than previously-reported hexagonal one and the possible reasons were discussed. Moreover, the effects of sacrificial reagents on the photocatalytic H 2 evolution were explored by using Na 2 S solution with different concentration.