Design of active interlayer space in layered oxysulfide photocatalysts NaMTiO2.2S1.8(M = lanthanoid) for efficient visible light hydrogen evolution

Abstract

Interlayer-active layered oxysulfides, which exhibit both interlayer hydration and ion-exchange capabilities, have recently emerged as a new class of visible-light-driven photocatalysts for water splitting. However, the utilization of interlayer galleries as reaction fields remains unexplored in oxysulfide photocatalysts. Here we demonstrate the interlayer space of a layered oxysulfide as an active reaction field for H₂ evolution. Interlayer-active layered oxysulfides NaMTiO_2.2S_1.8 (M = Pr, Nd, Sm, Eu, and Gd) were synthesized via a solid-state reaction, yielding submicrometer-sized particles suitable for effective utilization of the interlayer space, markedly smaller than those obtained by the previous H₂S-based method. Ni species were introduced into the active interlayer via ion-exchange with interlayer Na⁺. The interlayer-Ni-loaded NaMTiO_2.2S_1.8 exhibits significantly enhanced H₂ evolution activity compared with surface-Ni-loaded NaMTiO_2.2S_1.8, owing to more efficient utilization of photogenerated electrons within the particle interior. These results provide a new design concept for layered oxysulfide photocatalysts toward efficient visible-light-driven water splitting.