Improved H2-generation performance of Pt/CdS photocatalyst by a dual-function TiO2 mediator for effective electron transfer and hole blocking

Surface modification with noble metal cocatalysts was proved to be a useful route for boosting photocatalytic efficiency of various photocatalysts. Nevertheless, considering the random dispersion of metallic cocatalysts on the photocatalyst surface, the noble metal-loaded photocatalyst generally shows a limited enhancement of its activity because the noble metals can also work as the recombination sites of photoinduced charges. In this paper, TiO2 as a dual-function mediator (for effective electron transport and hole block) is successfully introduced into the interface of Pt and CdS to form Pt-TiO2/CdS photocatalyst, with an aim of suppressing the high recombination rate of electron-hole pairs on the Pt active sites. Under visible light, all the prepared Pt-TiO2/CdS displayed distinctly enhanced photocatalytic hydrogen-generation performance and the Pt TiO2/CdS(8%) attains the highest photocatalytic H-2-production rate (294.2 mu mol/h), a value significantly higher than that of Pt/CdS about 3.2 time. A dual-function TiO2-mediated mechanism was put forward to account for the superior hydrogen production of Pt-TiO2/CdS photocatalyst, namely, the TiO2 layer in the Pt-TiO2/CdS not only works as electron-transport layers to effectively transfer photogenerated electrons to promote the H-2-production reaction on Pt cocatalysts, but also acts as hole-block layer to prevent the possible recombination of photogenerated charges on the Pt active sites, resulting in a distinct improvement of final H-2-generation activity.