title: Engineering the TiO2 -graphene interface to enhance photocatalytic H2 production.
abstract: In this work, TiO2 -graphene nanocomposites are synthesized with tunable TiO2 crystal facets ({100}, {101}, and {001} facets) through an anion-assisted method. These three TiO2 -graphene nanocomposites have similar particle sizes and surface areas; the only difference between them is the crystal facet exposed in TiO2 nanocrystals. UV/Vis spectra show that band structures of TiO2 nanocrystals and TiO2 -graphene nanocomposites are dependent on the crystal facets. Time-resolved photoluminescence spectra suggest that the charge-transfer rate between {100} facets and graphene is approximately 1.4 times of that between {001} facets and graphene. Photoelectrochemical measurements also confirm that the charge-separation efficiency between TiO2 and graphene is greatly dependent on the crystal facets. X-ray photoelectron spectroscopy reveals that Ti-C bonds are formed between {100} facets and graphene, while {101} facets and {001} facets are connected with graphene mainly through Ti-O-C bonds. With Ti-C bonds between TiO2 and graphene, TiO2 -100-G shows the fastest charge-transfer rate, leading to higher activity in photocatalytic H2 production from methanol solution. TiO2 -101-G with more reductive electrons and medium interfacial charge-transfer rate also shows good H2 evolution rate. As a result of its disadvantageous electronic structure and interfacial connections, TiO2 -001-G shows the lowest H2 evolution rate. These results suggest that engineering the structures of the TiO2 -graphene interface can be an effective strategy to achieve excellent photocatalytic performances.
authors: Key Laboratory of Mesoscopic Chemistry of Ministry of Education, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093 (PR China).
authors: Lichen
authors: L
authors: Liu
authors: Zhe
authors: Z
authors: Liu
authors: Annai
authors: A
authors: Liu
authors: Xianrui
authors: X
authors: Gu
authors: Chengyan
authors: C
authors: Ge
authors: Fei
authors: F
authors: Gao
authors: Lin
authors: L
authors: Dong
mesh_terms: D002384:Catalysis; D004738:Engineering; D006108:Graphite / Q000737:chemistry*; D049329:Nanostructures / Q000737:chemistry; D055668:Photochemical Processes; D014025:Titanium / Q000737:chemistry*
chemical_list: C009495:titanium dioxide; D006108:Graphite; D014025:Titanium
keywords: H2 production; TiO2; crystal-facet effect; energy conversion; graphene; interfacial charge transfer