Facile Z-Scheme Photocatalyst Sheets Consisting of Metal Sulfides and Poly-3,4-ethylenedioxythiophene of a Conductive Polymer for Visible-Light-Driven Water Splitting

A Z-scheme photocatalyst sheet capable of water splitting under visible light was constructed by integrating a p-type (CuGa)0.5ZnS2 semiconductor for H2 evolution, a n-type CoOx-loaded BiVO4 photocatalyst for O2 evolution, and poly-3,4-ethylenedioxythiophene (PEDOT) as a solid-state hole transfer mediator on a fluorine-doped tin-oxide-coated glass (FTO) substrate. Water splitting proceeded under ambient temperature and 1 atm of argon, without pH adjustment. On the photocatalyst sheet employing a metal sulfide, PEDOT should be prepared by electrochemical oxidative polymerization of 3,4-ethylenedioxythiophene (EDOT) but not chemical oxidation with FeCl3 as an oxidant. Photoelectrochemical measurements revealed that PEDOT polymerized by electrochemical oxidation had a great hole transporting property to extract photogenerated holes smoothly from a (CuGa)0.5ZnS2 photocatalyst. Cu0.5Ga0.4In0.1ZnS2 (λ < 560 nm) and Cu3VS4 (λ < 830 nm) with responses to visible light with longer wavelengths than (CuGa)0.5ZnS2 (λ < 540 nm) were also applied to the sheet modified with PEDOT, achieving Z-schematic water splitting under visible light illumination.