Synthesis and Photocatalytic Activity of La5Ti2Cu(S1−xSex)5O7 Solid Solutions for H2 Production under Visible Light Irradiation

Abstract

AbstractThe effects of substituting selenide for sulfide ions in La5Ti2CuS5O7 were studied, with the aim of developing visible‐light‐driven photocatalysts with longer absorption edge wavelengths. La5Ti2Cu(S1−xSex)5O7 (LTCS1−xSexO) solid solutions were obtained over the composition range of 0≤x≤1 by a solid‐state reaction, and their physical properties and photocatalytic activities during the H2 evolution reaction in aqueous solutions were assessed. Structural refinements revealed that the lattice constants and cell volumes of the LTCS1−xSexO series follow Vegards’ law. With increases in the Se2− content, the LTCS1−xSexO absorption edge shifts monotonically toward longer wavelengths, to a maximum of 820 nm for LTCSeO (x=1). Those materials for which x≤0.8 generated H2 from aqueous solutions containing Na2S and Na2SO3 as electron donors under visible‐light irradiation (λ>420 nm) after surface modification with in situ precipitated NiS. Comparatively higher H2 evolution was observed for LTCS1−xSexO with lower Se2− levels, although the sample for which x=0.2 generated H2 under visible light at wavelengths longer than 640 nm, whereas the LTCSO did not.