Enhancing the hydrogen generation of TiO2nanoparticles by decorating its surface with BiI3and PbI2quantum dots

Abstract

This work reports the performance of TiO2/BiI3and TiO2/PbI2nanocomposites for hydrogengeneration. BiI3and PbI2quantum dots (QDs) were grown on TiO2(P25 Degussa) using a fastinjection method. According to the analysis by X-ray diffraction, the nanocomposites have a mixture of anatase, rutile and cubic phases from TiO2, BiI3and PbI2. The images obtainedfrom transmission electron microscopy revealed that the TiO2support have sizes in therange of 70e220 nm while the QDs of BiI3and PbI2(co-catalysts) grown on TiO2have sizesin the range of 12e17 nm. The presence of these iodides on TiO2created oxygen vacanciesdefects (confirmed by photoluminescence measurements) that extended the light ab-sorption of TiO2from the UV to the VIS range. According to the results from the photo-catalytic experiments for hydrogen generation (achieved using pure water and UV-VISlight), the hydrogen generation rates produced by the TiO2/BiI3and TiO2/PbI2nano-composites were 437e580 times, 81e108 times and 21e30 times, higher than these for pureTiO2, PbI2and BiI3, respectively. The maximum hydrogen generation rates of the TiO2/BiI3and TiO2/PbI2nanocomposites were 290.7 and 219.2mmol h 1g 1, respectively. In addition,the TiO2/BiI3and TiO2/PbI2nanocomposites contained defects that acted as electrontrapping centers, which in turn, delayed the electron-hole recombination and this favoredthe photocatalytic generation of H2. Moreover, the heterojunction formed between the TiO2and the iodides allowed the transfer of electrons from the conduction band of TiO2towardthe conduction band of the iodides, creating a“sink”for the electrons which delayed theelectron hole recombination. The results presented here demonstrated that the depositionof iodide co-catalyst on TiO2is a feasible option to enhance the hydrogen generation.