(Invited) Solid-State Z-Scheme Photocatalysts for Overall Water-Splitting Under Visible Light

Wednesday, 27 May 2015: 08:00
Lake Erie (Hilton Chicago)
H. Irie (Clean Energy Research Center, University of Yamanashi)
We fabricated an Ag-inserted hetero-junction photocatalyst for water-splitting under visible light, similar to a Z-scheme system but is not required for a redox mediator. In this system, Ag acts as a solid electron mediator for water-splitting. We selected ZnRh2O4 (Eg=1.2 eV) and AgSbO3 (Eg=2.5 eV) as H2- and O2-photocatalysts, respectively. Ag could be inserted between these photocatalysts using a thermal-decomposition reaction of Ag2O and following melt reaction of Ag. In short, commercially available powder of Ag2O and prepared powders of ZnRh2O4 and AgSbO3 were thoroughly mixed and heat-treated at 900oC, which is slightly lower than the melting temperature of Ag. Then, the obtained powder was washed with HNO3 aqueous solution to remove excess Ag, forming the solid-state photocatalyst, ZnRh2O4/Ag/Ag1-xSbO3-y. The Ag1-xSbO3-y and ZnRh2O4 particles were connected to each other with their particle sizes of ~1000 and ~200 nm. In this system, Ag acted as the solid-state electron mediator for the transfer of electrons from the conduction band of Ag1-xSbO3-y to the valence band of ZnRh2O4. Utilizing the constructed photocatalyst, the simultaneous liberation of H2 and O2 from pure water at a molar ratio of ~ 2:1 was achieved under irradiation with visible light at ~ 545 nm. Utilizing the same strategy by changing the O2-evolution photocatalyst, we recently succeeded in pure water-splitting under visible light up to 600 nm. Detailed investigations will be discussed at the conference.