Layered Metal Hydroxides and Their Derivatives: Controllable Synthesis, Chemical Exfoliation, and Electrocatalytic Applications

Layered metal hydroxides (LMHs) are regarded as a novel and important class of inorganic functional materials. They have unique layered structure and variable chemical compositions that can be readily tuned. In this review, summarized are the recent advances of synthetic routes to the LMHs with designed morphology, composition, and function for electrocatalysis. Versatile products can be readily derived by hybridization, anion-exchange, surface modification, self-assembly, etc. More importantly, LMHs can be artificially exfoliated into unilamellar nanosheets with a molecular-level thickness of about 1 nm versus 2D lateral size in submicrometer or micrometer scale. Molecular-scale assembly can be then applied to fabricate superlattice-like composites and functional nanofilms with high quality. The hydroxides can be transformed into oxides, nitrides, or other compounds via different preparation procedures, which can further extend their application prospects. In this regard, the most promising electrocatalysis-related applications of LMHs and their derivatives are reviewed, such as oxygen evolution reaction, oxygen reduction reaction, hydrogen evolution reaction, CO2 reduction reaction, alcohol or urea electrooxidation, etc. At last, future challenges are also discussed from the aspect of synthesis and application, as well as encouraging advancements are anticipated.