Dual effect of polypyrrole doping on cadmium sulfide for enhanced photocatalytic activity and robust photostability

After cadmium sulfide nanoparticles (CdS NPs) synthesized by a solvent-thermal precipitation method, a series of polypyrrole/CdS nanocomposites (PPy/CdS NCs) with different Py doping amounts were fabricated by in situ deposition oxidative polymerization. The encapsulated structure of PPy/CdS NCs was confirmed by field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS) indicates that the resulting CdS and optimal PPy/CdS-5 present low band gaps of 2.35 and 1.25 eV, respectively, which accounts for enhanced visible light response after PPy doping. Supporting by the results of photocatalytic performance and monitoring Cd2+ concentration by inductively coupled plasma optical emission spectrometer (ICP-OES), PPy/CdS NCs exhibit much higher photocatalytic performance on the degradation of rhodamine B (RhB) and methylene blue (MB) under visible light illumination than pristine CdS, which can be mainly attributed to enhanced stability as well as the photocatalytic activity of PPy/CdS NCs can be maintained without obvious decline after 10 cycles. PPy layer can effectively inhibit the occurrence of light corrosion of CdS itself. The possible mechanism about the improving photocatalytic activity from PPy doping and protection is also discussed.