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The development of graphitic carbon nitride (CN) based photocatalysts towards efficient visible light-driven H2 evolution is highly desired for solar energy conversion. It is well-known that bulk CN materials possess three intrinsic problems, namely, high charge recombination loss, low specific surface area, and limited sunlight harvesting range. To simultaneously overcome the abovementioned drawbacks of CN, we report an innovative multiple modification strategy, involving molecular grafting of the CN network, exfoliation to ultrathin nanosheets, and hybridization with TiO2 photocatalysts. The visible light utilization ability, specific surface area, and charge separation efficiency of the CN materials improved accordingly. As expected, the TiO2/CNX-NS heterojunction photocatalyst exhibited remarkably enhanced visible light-driven H2 production rate of 138.4 μmol h-1, which was about 4.6 times higher than that of pristine CN. The excellent photocatalytic performance under visible light confirmed the successful improvement in the corresponding drawbacks of CN by each modification. In this study, we propose the possibility of combining multiple modifications in the same system to synthesize an excellent visible light-driven photocatalyst for solar-to-fuel conversion.

As a promising photocatalyst, the large bandgap (3.2 eV) of anatase TiO2 seriously limits its light absorption of the UV portion of the solar spectrum, making it less applicable in industrial fields. A popular approach for enhancing visible light activity by narrowing the bandgap is doping, however, the dopant-induced defect states in the TiO2 lattice may act as recombination centers for the photogenerated charge carriers. Here we report a facile soft-chemical route to engineer the surface properties of TiO2 crystals using ethanol as the sole organic solvent. The individual TiO2 nanocrystals synthesized in the first step, possessing high affinity with ethanol molecules, tend to assemble together by interfacial Ti–Ti bonding during the following ethanol evaporation induced self-assembly process. Formation of Ti–Ti bonds at the interface simultaneously brings about the decrease of surface oxygen atoms in the TiO2 structural unit, which dramatically alters the electronic structure and extends the light absorption to ∼550 nm. Such a dopant-/additive-free TiO2 assembly exhibits considerable photocatalytic activity under visible light due to its narrower bandgap than individual nanocrystals. Further, an electron paramagnetic resonance measurement is used to confirm the capability of generating reactive ˙OH radicals on the surface of assembled TiO2 under visible-light irradiation.