CuOx based junctions e.g. CuOx-TiO2 have been demonstrated to be very effective in photocatalytic H2 production, but the active component at the junction is less understood. We herein report that an as-prepared CuOx-TiO2 photocatalyst undergoes an in situ restructuring process during photocatalytic H2 production under solar light irradiation to form the active Cu2O-TiO2 interfacial structure on the surface. These results unambiguously demonstrate that Cu2O is the active copper species in CuOx-TiO2 photocatalysts.

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P-type Cu2 O has been long considered as an attractive photocatalyst for photocatalytic water reduction, but few successful examples has been reported. Here, we report the synthesis of TiO2 (core)/Cu2 O (ultrathin film shell) nanorods by a redox reaction between Cu(2+) and in-situ generated Ti(3+) when Cu(2+) -exchanged H-titanate nanotubes are calcined in air. Owing to the strong TiO2 -Cu2 O interfacial interaction, TiO2 (core)/Cu2 O (ultrathin film shell) nanorods are highly active and stable in photocatalytic water reduction. The TiO2 core and Cu2 O ultrathin film shell respectively act as the photosensitizer and cocatalyst, and both the photoexcited electrons in the conduction band and the holes in the valence band of TiO2 respectively transfer to the conduction band and valence band of the Cu2 O ultrathin film shell. Our results unambiguously show that Cu2 O itself can act as the highly active and stable cocatalyst for photocatalytic water reduction.