Visible light-induced hydrogen production from glycerol aqueous solution on hybrid Pt–CdS–TiO2 photocatalysts

Binary (Pt/hex-CdS) and ternary (Pt/CdS/TiO2 and Pt/TiO2/hex-CdS) hybrid photocatalysts were evaluated in photoinduced reforming of glycerol under visible light irradiation (λ > 418 nm). The resulting hybrid materials are photocatalytically efficient with respect to hydrogen gas production. The relative order of reactivity for the synthesized hybrid catalysts was found to be: Pt/hex-CdS > Pt/CdS/TiO2 > Pt/TiO2/hex-CdS. The systems with CdS/aqueous solution interfacial contact showed higher activity, suggesting that the hydrogen production mechanism can be strongly influenced by hydrolytic surface reactions on CdS. The potential gradient created at the CdS/TiO2 or TiO2/hex-CdS interface may also play an important role in the photoelectrochemical mechanism. Therefore, carbonyl compounds such as acrolein and propanone, identified in the liquid phase after 7 h of irradiation, lead us to propose the first steps of a photoelectrochemical mechanism in the photoinduced reforming of glycerol.