Pb2Ti2O5.4F1.2 is a new photocatalyst that has recently been reported to function under visible light with suitable stability, albeit with insufficient photocatalytic activity. The present work demonstrates that the photocatalytic activity of Pb2Ti2O5.4F1.2 during visible-light-driven H2 evolution is improved following post-treatment with alkaline chlorides. The photocatalytic activity of the post-treated Pb2Ti2O5.4F1.2 was found to be greatly affected by both the type of alkaline chloride and the treatment temperature. Among the alkaline chlorides examined, a eutectic NaCl-CsCl mixture (35 : 65 molar ratio) was found to be the most effective. The optimized material, further modified with a Pt cocatalyst using an in situ photodeposition method with a H2PtCl6 precursor, showed approximately 10 times higher activity than that of an untreated analogue. The optimally modified Pb2Ti2O5.4F1.2 was also found to outperform Ru-loaded, Rh-doped SrTiO3, which is one of the most active metal oxide photocatalysts workable under visible light. Transient absorption spectroscopy indicated that the reactivity of photogenerated free and/or shallowly trapped electrons in the Pt-loaded, NaCl-CsCl-treated Pb2Ti2O5.4F1.2 with H2O was higher than that in an analogue not treated with the NaCl-CsCl mixture. Based on various physicochemical analyses, it is evident that the NaCl-CsCl treatment creates ion-exchangeable alkaline-titanate species on the catalyst surface that undergo proton-exchange during the photodeposition of Pt, leading to improved affinity for H2O. This effect explains the high activity of the NaCl-CsCl-treated Pb2Ti2O5.4F1.2 during H2 evolution under visible light.
ASJC Scopus subject areas
- Renewable Energy, Sustainability and the Environment
- Materials Science(all)