Recent advances in the synthesis of layered double hydroxides nanosheets

Layered double hydroxide (LDH) with characteristic two-dimensional structure and positive layer charge has attracted attention in a wide range of applications in recent years. Although LDH with a layer-by-layer structure has high applicability as a catalyst, adsorbent, drug reservoir, and so on, it has been suggested that the single-layered LDH nanosheets not only enhance the performance but also expand the application in electrocatalyst, batteries, and supercapacitors due to the increased active sites in nanosheets. In this review, we introduced state of the art in the synthesis of LDH nanosheets in terms of synthesis approaches, mechanisms, and properties of thus obtained LDH nanosheets. The synthesis approaches are primarily categorized into two parts, namely, top-down synthesis to delaminate bulk LDH and bottom-up synthesis to obtain single-layer LDH in limited space. In the first section, the exfoliation of LDH, which was realized by weakening the layer-by-layer stacking and by increasing the basal distance, was summarized mainly based on the swelling mechanism. In the second section, the bottom-up syntheses of LDH nanosheets through controlled crystal growth in confined space or restricted synthetic conditions are introduced.