Z-Schematic Water Splitting on Photocatalyst Sheets Composed of Transition-Metal-Doped Metal Oxides with Long Wavelength Visible Light Responses and a Conductive Polymer

Abstract

We successfully developed Z-schematic photocatalyst sheets consisting of transition-metal-doped oxide materials responding to visible light with long wavelengths as O2-evolving photocatalysts and poly-3,4-ethylenedioxythiophene (PEDOT) of a conductive polymer as a solid-state hole transporter combined with Ru-loaded SrTiO3:Rh as a H2-evolving photocatalyst for water splitting under visible light irradiation by a facile drop-casting method. TiO2:Rh,Sb (EG: 1.9-2.3 eV), SrTiO3:Ru,Sb (EG: 1.8 eV), and SrTiO3:Ir,Sb (EG: 1.6-1.8 eV) were employed as O2-evolving photocatalysts that are responsive to visible light with longer wavelengths than BiVO4 (BG: 2.4 eV) of a conventional O2-evolving photocatalyst. The Z-scheme photocatalyst sheets composed of these O2-evolving photocatalysts split water into H2 and O2 in a stoichiometric amount under visible light irradiation at room temperature and 1 atm even without pH adjustment. In particular, the photocatalyst sheet composed of TiO2:Rh,Sb showed the highest Z-schematic water splitting activity under visible light among the sheets composed of other transition-metal-doped photocatalysts. Furthermore, the control experiments using 3-type light emitting diodes (λ = 450, 525, and 590 nm) revealed that the new Z-scheme photocatalyst sheet using TiO2:Rh,Sb could utilize visible light with long wavelengths compared with that using BiVO4