Recent developments in layered double hydroxide structures with their role in promoting photocatalytic hydrogen production: A comprehensive review

Layered double hydroxides (LDHs) have received scientific attractions due to their unique two-dimensional (2D) structure, band gap tunability, and compositional flexibility, leading to the facile incorporation of the metal species into their layered structure. The main objective of this review is to explore the current advancement of LDH-based photocatalysts for photocatalytic hydrogen production by focusing on the role of divalent and trivalent metal incorporations and their efficiency enhancement. Firstly, the mechanism of photocatalysis and its thermodynamics has been explicated to gain basic understanding and fundamentals. Secondly, a brief introduction to the overview of LDH photocatalysts with special attention to the effects of cationic incorporations on the optical properties and computational study towards the electronic density has been demonstrated. Besides, the thermal stability of LDH is briefly discussed, focusing on the effects of temperature towards the conversion into mixed-metal oxide (MMO). Next, the classification of LDH based on divalent and trivalent cationic elements and their role in the brucite layer of LDH are systematically discussed. Attention is given to the mechanistic properties of the extensively studied metals, such as Mg, Ni, Zn, Co, Cr, Fe, V and Al, with the efficiency enhancements through various engineering aspects are demonstrated. The overview summary on the efficient design of LDH is elucidated to provide a deep understanding for improving their photocatalytic properties. Lastly, the future perspectives and recommendations are discussed to provide new insight into the potential of LDH and render them a notable place in solar energy applications.