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

Abstract

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.

Ultrathin Ni(OH)2 layer coupling with graphene for fast electron/ion transport in supercapacitor

“…Among the electrode materials for supercapacitors, transition metal hydroxides/oxides (e.g., Co(OH) 2 , Ni(OH) 2 , RuO 2 , MnO 2 , NiO, and Co 3 O 4 ) [31][32][33][34][35][36], exhibit unique merits, such as high theoretical capacitance, reversible redox reaction, and multiple oxidation states. Thereinto, nickel hydroxide is an attractive material, thanks to its cost-effectiveness, well-defined redox behavior, high theoretical capacitance (2082 F g −1 ) and ecofriendliness [37][38][39]. Wei et al [40] prepared an assembly of flower-like Ni(OH) 2 under mild conditions.…”

Atomic Thickness Catalysts: Synthesis and Applications

“…[18,25] For instance, Guo's group successfully prepared a free-standing PdMo bimetallene with a thickness of 4-atom, giving a significantly higher atomic utilization >0.5 and a much larger mass activity of oxygen reduction reaction compared with commercial Pt/C and Pd/C, respectively. [18] To date, the 2D layered nanostructures, [26][27][28][29] multimetallic nanomaterials [1,17] and ultrathin 2D nanomaterials [19] have been reported in several reviews and most of them offered a certain range of materials (e.g., 2D materials, metallic materials, layered materials). While a fraction of exemplified materials in these reviews were related with atomically thin catalysts (less than 5 nm thickness).…”

“…[19,30] Graphene, an atomically thin 2D layered material, has attracted numerous attentions in diversely catalytic applications due to the ultrahigh specific surface area and high electrical conductivity. [31][32][33][34] Meanwhile, other layered ATCs have been developed as well, for example, transition metal dichalcogenides (TMDs), [20,[35][36][37][38][39] MXenes, [40,41] layered double hydroxides (LDHs), [9,27,42,43] graphdiynes (GDY), [44,45] etc. In addition, extensive researches on nonlayered nanostructured ATCs further enriched the exploration of ATCs family members.…”

“…Liquid phase exfoliation (LPE) method is extremely costeffective and versatile, which is mostly confined to the layered materials, like graphene, [13] TMDs, [99] LDHs [27] and antimony (Sb). [100,101] While this method shows disadvantages in the formation of particles as well as the incomplete exfoliation efficiency, inducing low production of atomic thin layers.…”

Hydrothermal control, characterization, growth mechanism, and photoluminescence properties of highly crystalline 1D Eu(OH)3 nanostructures

“…The physical and chemical properties of nanomaterials mainly depend on their size, crystal form, and morphology; thus, materials bearing differences in these characteristics may show different properties even if they have the same chemical composition. The controlled synthesis of nanomaterials with different structures and geometric characteristics is an important challenge in efforts to obtain improved performance 1,2 from nanowires, nanorods, nanotubes, and nanobelts. Indeed, the synthesis of 1D nanomaterials is of particular interest because they may provide a foundation for the subsequent construction of nano-functional devices because of their quantum connement effect.…”