Efficient charge separation is of crucial importance for the improvement of photocatalytic activity for solar hydrogen evolution. Here we report efficient photo-generated charge separation by twin-induced one-dimensional homojunctions with type-II staggered band alignment, using a ternary chalcogenate, i.e. Cd 0.5 Zn 0.5 S nanorod as a model material. The quantum efficiency of solar hydrogen evolution over this photocatalyst, without noble metal loading, reaches 62%. Unlike traditional heterojunctions, doping or combination of additional elements are not needed for the formation of this junction, which permits us to tune the band structures of semiconductors to the specific application in a more precise way. Our results highlight the power of forming long-range ordered homojunctions at the nanoscale for photocatalytic and photoelectrochemical applications.

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For photocatalytic solar energy conversion, the critical challenge is to enhance the solar utilization efficiency. Many efforts have focused on the development of broad-band response nanomaterials. Here, we propose an alternative approach wherein, over Ni 2 P/ TiO 2 nanoparticles without noble metal, the UV−vis part of solar energy was absorbed and converted by a semiconductor and its infrared part was separately collected and converted into thermal energy to heat the photocatalytic reaction to a certain temperature. The photothermocatalytic hydrogen activity was 3.6 times that of the sum of the photocatalytic and thermocatalytic reactions. The in situ generated oxygen vacancies in Ni 2 P/TiO 2 during the photothermocatalytic reaction were found to be responsible for the enhanced activity. Moreover, the photocurrent transient response results revealed the faster transfer of electrons from TiO 2 to Ni 2 P at higher temperature which is vital for the significantly enhanced photothermocatalytic hydrogen production. The long-term test also shows the stability of the proposed reaction system.

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