Preparation Of ZnO-based Core/Shell Nanorods Grown On RGO Sheets And Its Photocatalytic Performance

In this paper, ZnO nanorods were prepared by a low temperature hydrothermalgrowth, and Ag2O, CuO or In2O3was deposited on ZnO nanorods by impregnation orphotocatalytic deposition. ZnO nanorods/RGO nanocomposites were also synthesizedby the hydrothermal treat of ZnO seed layer on RGO sheet. Based on the as-preparedZnO nanorods/RGO nanocomposites, ZnO nanorods in nanocomposites wereconverted to ZnO@ZnS and ZnO@ZnS-Bi2S3core/shell nanorods. Themorphologies, crystal structure, distribution of components, photo absorption, andphotocatalytic performance of these nanocomposites were characterized by usingSEM, TEM, XRD, XPS, FT-IR, Raman, PL, UV-Vis, CV, EIS. Moreover, theenergy band structure of catalysts and the reaction mechanism of photocatalytichydrogen production were also discussed.ZnO/MOx?M=Ag, Cu or In?core/shell nanorods with the length of about2?mand the diameter of about150nm are fabricated by coating the ZnO nanorods with alayer of oxide composite shell mainly consisting of nanoparticles of10-20nm.Theresults show the deposition of P type semiconductor (Ag2O, CuO and In2O3) canobviously improve the photo absorption performance and photocatalytic hydrogenproduction rate, which is related to the formation of the p-n heterojunction to repressrecombination of the photoinduced hole–electron pairs of ZnO.The studies on RGO/ZnO nanaocomposites show that the calcinationtemperatures of ZnO leed layer have a significant impact on the morphology,structure and photocatalytic performance. When the temperature of ZnO seed layer ishigher than300oC, the3dimesion structure of ZnO nanorods grown on RGO sheetscan be formed due to the strong chemical interaction between RGO and ZnO, and theformation of Zn-O-C bond, which can accelerate the transfer of photo-generatedcharges and improve the separation efficient of photot-generated electron-hole pairs.As a result, RGO/ZnO nanaocomposites exhibit much higher photocatalytic hydrogenproduction rate as compared to ZnO nanorods.The results show that RGO/ZnO@ZnS-Bi2S3, consisting of ZnO@ZnS-Bi2S3core/shell nanorods anchored on RGO sheets, were obtained via combining ahydrothermal growth, liquid-phase chemical conversion and ion exchange. The TEMimages show that the length of nanorod is200~300nm, the diameter is50~60nm, and thickness is5-8nm.The as-prepared RGO/ZnO@ZnS-Bi2S3core-shell nanorodsdisplay a wide and strong photo absorption in visible region and exhibit a higherphotocatalytic activity for H2evolution from the glycerol water mixtures as comparedto the RGO/ZnO nanorods and RGO/ZnO@ZnS core/shell nanorods. Under theoptimal Bi2S3/ZnS molar ratio in the shell layer, the highest photocatalytic hydrogenproduction rate of15.5?mol h-1is observed. The highly improved performance of thecomposites can be ascribed to the increased light absorption and efficient chargeseparation.