We have synthesized different mass ratios of effectively-contacted TiO2/bulk g-C3N4 composites (T/CN) by a wet chemical method, and evaluated their photocatalytic activities for degrading acetaldehyde and producing H-2. It is clearly demonstrated by means of surface photovoltage responses and photoluminescence spectra that the photogenerated charge carriers in the T/CN nanocomposites with a proper mass ratio of T display much higher separation in comparison to CN alone. This is well responsible for the enhanced photocatalytic activities of CN after coupling with nanocrystalline anatase TiO2. Interestingly, it is also applicable to the resulting CN nanosheet (about 3 nm) with higher photoactivity than the bulk one. As a result, the TiO2/CN-nanosheet composites as efficient photocatalysts have been successfully developed. Moreover, it is confirmed that the enhanced photoactivity for resulting nanocomposites are attributed to the promoted charge transfer and separation from CN to TiO2. (C) 2015 Elsevier Ltd. All rights reserved.