Layered double hydroxide-based composites for catalysis: a review of morphology and structure modification strategies

Layered double hydroxides (LDHs), typical of inorganic layered particles, have revealed prodigious potential in many applications, including electrocatalysis and photocatalysis (energy catalysis). However, most of the existing studies pursue the optimization of LDH functions from the perspective of laminate composition, interlaminar anionic species and particle size, and pay less attention to the influence of LDH morphology and structure on performance. Herein, starting from a short overview of LDH fundamental structure and characteristics, we move on to a comprehensive study of the preparation methods of conventional hexagonal sheets, and the special LDH morphology (spherical, polyhedral, nanowire, ring, etc.). Considering the need to combine LDH with other functional groups to improve their overall performance, the regulation of LDH composite morphology—according to the reaction type, synthesis conditions and matrix surface properties is analyzed in depth and examined. Also, the applications of LDH and its composites as electro/photocatalytic materials are discussed. More precisely, the article focuses on the current developments in the modification of LDHs, specifically their electronic structure, morphology, interfacial interactions and synergistic catalytic impact with noble metal catalysts to improve catalytic performance. Finally, the review article terms out future directions as well as the main issues and directions upon rational design and practical implementation of LDH-based materials in energy catalysis.