From Nanorods to Nanowires of CdS Synthesized by a Solvothermal Method: Influence of the Morphology on the Photoactivity for Hydrogen Evolution from Water

Abstract

Abstract:The effect of temperature and water/thiourea ratio on the growth, crystallinity and morphological characteristics of CdS nanostructures synthetized by a solvothermal method using ethylenediamine as solvent were studied. The temperature and water/thiourea ratio used in the synthesis determine the surface area, shape, length and degree of crystallinity of the CdS nanostructures obtained. Nanowires of high crystallinity and length were obtained when the solvothermal synthesis was performed at 190˝C, while nanorods with lower length and crystallinity were obtained as the solvothermal temperature decreased to 120˝C. The change in the water/thiourea ratio affects the crystallinity and length of the CdS nanostructures to a lesser extent than temperature. Nevertheless an increase in the water/thiourea ratio used during the solvothermal synthesis resulted in CdS nanorods with higher crystallinity, lower aspect ratio and lower specific surface area. Textural, structural and surface properties of the prepared CdS nanostructures were determined and related to the activity results in the production of hydrogen from aqueous solutions containing SO 3 2´+ S 2ú nder visible light.

CdS Photocatalysts Modified with Ag: Effect of the Solvothermal Temperature on the Structure and Photoactivity for Hydrogen Production

“…Silver was added in a molar ratio equal to 0.05 mol Ag/0.95 mol Cd. As described in previous works [3] the solvothermal synthesis was performed using a Teflon-lined stainless steel autoclave filled up with the precursors dissolved in 100 mL of ethylenediamine (EDA). The solvothermal conditions established for the experiments are analogous to those described in our previous work [20], maintaining the autoclave for 12 h at the selected temperatures: 90, 120, 150, and 190 • C. The obtained yellow precipitates suspended in the solvent were washed with distilled water and ethanol several times and dried under vacuum (70 • C, 0.008 bar, 2 h) in order to get the solid powders.…”

“…To date, a large number of materials (oxides, sulfides, nitrides, oxynitrides, oxysulfides) have been developed for this application [1,2]. Among the most efficient materials, the CdS stands out because of its narrow band gap and the position of its valence and conduction bands that allow the absorption of a wide range of the solar light spectrum [3][4][5]. The main challenge in the development of photocatalysts based on CdS is to improve its efficiency bringing it to the value required for the practical production of hydrogen.…”

Photocatalytic Activities of Copper Doped Cadmium Sulfide Microspheres Prepared by a Facile Ultrasonic Spray-Pyrolysis Method

“…Over the past decades, metal sulfides [2] and chalcogenides [3] have attracted broad interest from scientists engaged in photocatalysis. Of those compounds, cadmium sulfide (CdS) is an attractive semiconductor photocatalyst under continuous research due to its optimal band gap and suitable position of the conduction band and valence band edge [4,5,6]. Various CdS nanostructures or combinations were applied as photocatalysts for solar hydrogen production [7,8,9].…”

Role of the Sulphur Source in the Solvothermal Synthesis of Ag-CdS Photocatalysts: Effects on the Structure and Photoactivity for Hydrogen Production

“…The physicochemical characterization of the CdS-X and AgCdS-X photocatalysts has revealed the strong impact of the sulphur source over the structure and photoactivity of the photocatalysts. It is well-known that the formation of CdS nanostructures under solvothermal conditions follows the solvent coordination molecular template (SCMT) model [38,39,44] in which the ethylenediamine acts as solvent and structure director agent. According to this model the changes in the morphology and structure of the CdS particles are related with the metal (Cd 2+ and Ag + ) complexation [67][68][69][70] and the S 2− generation rate because both factors determine the nucleation and crystallization of the final nanostructures of CdS [43,51,71].…”

“…The growth, nanomorphology and crystal structure of the CdS prepared by solvothermal method depend on the time, temperature [34][35][36][37], solvent [38,39] and precursors [40][41][42][43] used in the synthesis. In our previous work, Vaquero et al [38,39] proposed a systematic study employing different solvents, and it was found that ethylenediamine is an optimal solvent to control the growth, morphology and crystal structure of the CdS. Another important parameter in the control of the nanostructure is the solvothermal temperature of synthesis.…”