Metal oxide/2D layered TMDs composites for H2 evolution reaction via photocatalytic water splitting – A mini review

Abstract

H2 plays a crucial role in the energy demanding economy which makes it essential to develop materials for its production by water splitting using earth abundant resources. Water is split into H2 and O2 by using thermal energy-thermolysis, electrical energy-electrolysis, or photon energy-photocatalysis. Among them, the semiconductor based photocatalytic water splitting is a simple technique to produce H2 fuel utilizing water and solar energy. Several factors such as band gap alignment, light absorption ability, morphology, and stability influence the efficiency of the photocatalyst. The traditional noble metal and metal oxide based catalyst has some practical difficulty in achieving the overall water splitting, due to the fast recombination of photogenerated charges. This made researchers explore the 2D transition metal dichalcogenides as photocatalyst for H2 production by water splitting owing to their large surface area, excessive adsorption catalytic sites, high carrier mobility and short carrier migration distance. In this regard, the discovery of MoS2 especially paved the way to a new class of 2D transition metal dichalcogenides (TMDs) used as co-catalyst in photocatalytic water splitting. This new class of TMDs played a vital role to enhance the photocatalytic water splitting by acting as a medium for fast charge transfer thereby retarding the recombination of the photogenerated holes and electrons. The tunable band gap, wide absorption ranges, and semimetallic to semiconducting properties of the TMDs have attracted great interest as materials for photocatalysis. Further, the construction of metal oxide/TMDs heterostructures enhanced its efficiency by forming a Z-scheme heterojunction facilitating the mobility and separation of photogenerated charges. In this review, we attempt to sum up the different metal oxide/TMDs heterostructure composite based photocatalysts for efficient H2 production. The reason behind the enhancement of H2 production and the mechanisms are viewed very concisely for the constructed heterostructure composites. Further we also highlight some challenges, drawbacks, and the future perspective for the effective photocatalytic water splitting.