Abstract
A combination of atomic layer deposition (ALD) and sol-gel techniques was applied to fabricate a direct Z-scheme Ta <sub>3</sub> N <sub>5</sub> -WO <sub>2.72</sub> heterojunction film photocatalyst for improved H <sub>2</sub> generation. The Ta <sub>3</sub> N <sub>5</sub> was deposited by ALD on WO <sub>2.72</sub> sol coated on Si wafer. Ta <sub>3</sub> N <sub>5</sub> film coated on bare Si wafer showed 13.2 μmol/g of H <sub>2</sub> generation after 6 h under irradiation by a 150 W Xe lamp with a cut-off filter (λ > 420 nm). In comparison, the direct Z-scheme Ta <sub>3</sub> N <sub>5</sub> -WO <sub>2.72</sub> heterojunction film demonstrated a more than two-fold increase in H <sub>2</sub> production (31.9 μmol/g). The efficiency of the Ta <sub>3</sub> N <sub>5</sub> -WO <sub>2.72</sub> heterojunction film further increased to 46.4 μmol/g upon coating with Pt nanoparticles by ALD. Additionally, the direct Z-scheme Ta <sub>3</sub> N <sub>5</sub> -WO <sub>2.72</sub> heterojunction film generated 18 times more H <sub>2</sub> than a Ta <sub>3</sub> N <sub>5</sub> -WO <sub>3</sub> liquid-state (using NaI as the shuttle redox mediator) Z-scheme system prepared by mixing Ta <sub>3</sub> N <sub>5</sub> and WO <sub>3</sub> powders. The H <sub>2</sub> generation of the direct Z-scheme Ta <sub>3</sub> N <sub>5</sub> -WO <sub>2.72</sub> heterojunction film coated with Pt nanoparticles further increased to 3072.5 μmol/g without the 420 nm cut-off filter.