CdS photocatalysts loaded with Ag 2 S and MoS 2 as dual co-catalysts were prepared via a one-step in situ hydrothermal method using CdCl 2 Á2.5H 2 O, H 2 MoO 4 , AgNO 3 Á9H 2 O, and CS(NH 2 ) 2 as the raw materials. The as-prepared photocatalysts were characterized by X-ray diffraction, scanning electron microscopy, transmission electron micrograph, X-ray photoelectron spectroscopy, photoluminescence spectra, and UltravioletVisible diffuse reflectance spectroscopy (UV-Vis DRS). The highest photocatalytic degradation rate was achieved for Ag 2 S/MoS 2 /CdS composites (87 %) compared to MoS 2 /CdS composites (66 %) and CdS (62 %) under visible light illumination for 60 min. The recycled photocatalytic experiments showed that the photocatalytic stability of CdS was improved with the introduction of Ag 2 S and MoS 2 . The improved photocatalytic performance of Ag 2 S/ MoS 2 /CdS composites can be ascribed to the red shift of absorption edge, enhanced light absorption intensity, and the increased separation of the photoinduced electron-hole pairs, which was attributed to the synergetic effect of MoS 2 and Ag 2 S on CdS. It was proven that Ag 2 S and MoS 2 can act as effective dual co-catalysts to enhance the photocatalytic degradation activity of CdS.
Herein, we report the successful formation of graphitic carbon nitride coated titanium oxide nanotube array thin films (g-C3N4/TiO2) via the facile thermal treatment of anodized Ti sheets over melamine. The proportion of C3N4 and TiO2 in the composite can be adjusted by changing the initial addition mass of melamine. The as-prepared samples are characterized by several techniques in order to understand the morphological, structural, compositional and optical properties. UV-vis absorption studies exhibit a remarkable red shift for the g-C3N4/TiO2 thin films as compared to the pristine TiO2 nanotubes. Importantly, the prepared composites exhibit an enhanced photocurrent and photo-potential under both UV-vis and visible light irradiation. Moreover, the observed maximum photo-conversion efficiency of the prepared composites is 1.59 times higher than that of the pristine TiO2 nanotubes. The optical and electrochemical impedance spectra analysis reveals that the better photo-electrochemical performance of the g-C3N4/TiO2 nanotubes is mainly due to the wider light absorption and reduced impedance compared to the bare TiO2 nanotube electrode. The presented work demonstrates a facile and simple method to fabricate g-C3N4/TiO2 nanotubes and clearly revealed that the introduction of g-C3N4 is a new and innovative approach to improve the photocurrent and photo-potential efficiencies of TiO2.
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