Visible-Light-Responsive CuLi1/3Ti2/3O2 Powders Prepared by a Molten CuCI Treatment of Li2TiO3 for Photocatalytic H2 Evolution and Z-Schematic Water Splitting

CuLi1/3Ti2/3O2 powders with hexagonal- and trigonal-delafossite structures were prepared by treating cubic-Li2TiO3 and monoclinic-Li2TiO3 with molten CuCl, respectively. It was confirmed that Li+ at the interlayer of Li2TiO3 was replaced with Cu(I). Both hexagonal- and trigonal-CuLi1/3Ti2/3O2 showed photocatalytic activities for sacrificial H2 evolution using visible light up to 600 nm which corresponds to their absorption edges (BG 2.1 eV), when Ru- and Pt-cocatalysts were loaded. The activity of the hexagonal-CuLi1/3Ti2/3O2 was higher than that of the trigonal-CuLi1/3Ti2/3O2. The apparent quantum yield of the sacrificial H2 evolution from an aqueous K2SO3 + Na2S solution over the hexagonal-CuLi1/3Ti2/3O2 loaded with Ru-cocatalyst was 3.3% at 420 nm. Moreover, Z-schematic water splitting was achieved when hexagonal- and trigonal-CuLi1/3Ti2/3O2 with a Pt-cocatalyst as H2-evolving photocatalysts were combined with a reduced graphene oxide (RGO)-TiO2 composite as an O2-evolving photocatalyst.