In-Situ Synthesis of Hydrogen Titanate Nanotube/Graphene Composites with a Chemically Bonded Interface and Enhanced Visible Photocatalytic Activity.

Hydrogen titanate nanotube (HTT)/graphene nanocomposites are synthesized by hydrothermal reduction of graphene oxide (GO) and simultaneous preparation of nanotubular HTT via an alkaline hydrothermal process. By using this facile in-situ compositing strategy, HTT are densely supported upon the surface of graphene sheets with close interface contacts. The as-prepared HTT/graphene nanocomposites possess significantly enhanced visible light catalytic activity for the partial oxidation of benzylic alcohols. The amount of graphene has significant influence on catalytic activity and the optimal content of graphene is 1.0 wt %, giving a normalized rate constant of 1.71 × 10 g/m²·h, which exceeds that of pure HTT and HTT/graphene-1.0% mixed by a factor of 7.1 or 5.2. Other than the general role of graphene as a high-performance electron acceptor or transporter, the observed enhancement in photocatalytic activity over HTT/graphene can be ascribed to the improved interfacial charge migration from enhanced chemical bonding (Ti-C bonds) during the in-situ compositing process. The formation of Ti-C bonds is confirmed by XPS analysis and the resulting enhanced separation of photoinduced charge carriers is demonstrated by electrochemical impedance spectra and transient photocurrent response.