Abstract
Ultrasonic spray pyrolysis is a superior method for preparing and synthesizing spherical particles of metal oxide or sulfide semiconductors. Cadmium sulfide (CdS) photocatalysts with different sizes and doped-CdS with different dopants and doping levels have been synthesized to study their properties of photocatalytic hydrogen production from water. The CdS photocatalysts were characterized with scanning electron microscopy (SEM), X-ray fluorescence-spectrometry (XRF), UV-Vis absorption spectra and X-ray diffraction (XRD) to study their morphological and optical properties. The sizes of the prepared CdS particles were found to be proportional to the concentration of the metal nitrates in the solution. The CdS photocatalyst with smaller size showed a better photocatalytic activity. In addition, Cu doped CdS were also deposited and their photocatalytic activities were also investigated. Decreased bandgaps of CdS synthesized with this method were found and could be due to high density surface defects originated from Cd vacancies. Incorporating the Cu elements increased the bandgap by taking the position of Cd vacancies and reducing the surface defect states. The optimal Cu-doped level was found to be 0.5 mol % toward hydrogen evolution from aqueous media in the presence of sacrificial electron donors (Na2S and Na2SO3) at a pH of 13.2. This study demonstrated that ultrasonic spray pyrolysis is a feasible approach for large-scale photocatalyst synthesis and corresponding doping modification.
Highlights
Photocatalytic water splitting has continuously been a hot academic topic since Fujishima and Honda1 s work in hydrogen production from water using a TiO2 electrode [1]
The UV-Vis absorption spectrum, crystalline phase, fluorescence properties and photocatalystic activities of Cadmium sulfide (CdS) or doped CdS photocatalysts were tested to investigate the effect of particle-sizes, dopant and doping level on their structural, optical and photocatalytic properties
It was found that the particle sizes increase with increasing starting-solution concentration and the surface of CdS particles is rather rough because it originates from aggregation of primary particles [22]
Summary
Photocatalytic water splitting has continuously been a hot academic topic since Fujishima and Honda s work in hydrogen production from water using a TiO2 electrode [1]. Various CdS nanostructures or combinations were applied as photocatalysts for solar hydrogen production [7,8,9] One drawback of this material is the photocorrosion by the photogenerated holes from the valence band of the CdS during the photocatalytic reaction in aqueous solution. It is reported that spray pyrolysis is an efficient way to prepare sulfides or oxides microspheric powder or films [22,23,24] With this method, one can synthesize micro-particles of different sizes which range from submicrometers to micrometers by controlling the various concentrations of metal nitrates in their starting aqueous solution. The UV-Vis absorption spectrum, crystalline phase, fluorescence properties and photocatalystic activities of CdS or doped CdS photocatalysts were tested to investigate the effect of particle-sizes, dopant and doping level on their structural, optical and photocatalytic properties
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