A brief review on modified layered double hydroxides for H2 production through photoinduced H2O splitting

Abstract

Layered double hydroxides (LDH), two dimensional (2D) layered nanostructured materials usually known as hydrotalcites, anionic clays, or host-guest compounds have attracted significant research interest in the photocatalysis field. Their photocatalytic behavior is attributable to their large specific surface area, high surface to volume ratio, tunable electronic and structural composition, highly dispersed metal (divalent, trivalent, or tetravalent) octahedrons linked to one another through metal oxo-bridge linkage undergoing certain transitions like d-d transitions, metal to metal charge transfer and ligand to metal charge transfer. Their photoactive response can be further improved through certain modifications like doping of particular cation, specific anion intercalation, calcination, heterostructure formation with other semiconductors, and noble metal loading generally providing a wider light response, inhibited recombination and longer lifetime of electron-hole pairs, shorter charge transfer distance, and increased specific surface area in some cases. Among various photocatalytic applications, hydrogen production through water splitting is an emerging area of research on account of rising energy crises with growing civilization. LDHs with highly attractive features are not at the backfoot for such pivotal zone, but are being extensively utilized as bare or modified for the reduction of water under light illumination. This review is aimed to illustrate the photocatalytic performance of LDHs with several adapted modifications to their structural and electronic properties and focused on their execution towards hydrogen production through photoinduced water splitting. To start with, brief information is provided about their commonly used synthetic methods, composition, structure, and key characteristics. Then, their photocatalytic properties are discussed with some specific examples for different applications and individual discussion with mechanistic approach is carried out that how certain modification to their original structure can bring improvement in their photactivity. At last, all the past and recent progress of LDHs is provided with proper mechanistic understanding for photocatalytic hydrogen production.