Fabrication of Ta3N5-ZnO direct Z-scheme photocatalyst for hydrogen generation

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. Ta3N5 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 Ta3N5 to form a direct Z-scheme structure, ZnO Ta3N5. The ALD cycle number varied from 200 to 500. All of the direct Z-scheme samples exhibited much higher hydrogen evolution efficiencies than Ta3N5, ZnO, and the indirect Z-scheme, with the order of ZnO300@Ta3N5>ZnO200@Ta3N5>ZnO400@Ta3N5>ZnO500@Ta3N5. Because of the uniform distribution, discrete particles, and proper size of ZnO, ZnO300@Ta3N5 showed the highest hydrogen evolution rate, being about 500 mu mol/g-h. With 400 or 500 ALD cycles, the larger particles of ZnO would overlap with each other to form a continuous layer on Ta3N5, thus reducing the exposure of Ta3N5 to the light and water for producing hydrogen. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.