摘要
Based on the Z-scheme mechanism, the combination of two semiconductors with suitable bandgaps can reduce the recombination rate of electrons and holes in a single material to enhance photocatalytic hydrogen evolution. Ta <sub>3</sub> N <sub>5</sub> with suitable band gap positions is a potentially promising material for photocatalysis. In order to raise the hydrogen production rate, ZnO nanocrystals were deposited by atomic layer deposition (ALD) on Ta <sub>3</sub> N <sub>5</sub> to form a direct Z-scheme structure, ZnO@Ta <sub>3</sub> N <sub>5</sub> . The ALD cycle number varied from 200 to 500. All of the direct Z-scheme samples exhibited much higher hydrogen evolution efficiencies than Ta <sub>3</sub> N <sub>5</sub> , ZnO, and the indirect Z-scheme, with the order of ZnO300@Ta <sub>3</sub> N <sub>5</sub> >ZnO200@Ta <sub>3</sub> N <sub>5</sub> >ZnO400@Ta <sub>3</sub> N <sub>5</sub> >ZnO500@Ta <sub>3</sub> N <sub>5</sub> . Because of the uniform distribution, discrete particles, and proper size of ZnO, ZnO300@Ta <sub>3</sub> N <sub>5</sub> showed the highest hydrogen evolution rate, being about 500 μmol/g-h. With 400 or 500 ALD cycles, the larger particles of ZnO would overlap with each other to form a continuous layer on Ta <sub>3</sub> N <sub>5</sub> , thus reducing the exposure of Ta <sub>3</sub> N <sub>5</sub> to the light and water for producing hydrogen.