Hybrid layered double hydroxides as multifunctional nanomaterials for overall water splitting and supercapacitor applications

Global demand for energy conversion and storage technologies such as fuel cells, water electrolyzers, batteries, and supercapacitors is increasing, yet their commercial and environmental viability are critically dependent on the performance of their electrode materials and catalysts, which are the indispensable components that drive these systems. Among various materials, layered double hydroxides (LDHs) are considered promising candidates for catalysts and electrodes for electrochemical energy conversion and storage systems. Their diverse range of chemical properties make them highly versatile platforms for developing hybrid nanostructures, including flexible two-dimensional LDH nanostructures with various di-/tri-valent metals. Hybrid LDHs also exhibit unique structural attributes, including 3D hierarchical porous features and heterointerfaces, as well as optimized electrical conductivity and stability, which are crucial to achieving highly efficient multifunctional nanomaterials for electrochemical energy device applications. This review presents recent developments in the design, synthetic routes, structural/chemical modification strategies, and applications of hybrid LDHs as multifunctional nanomaterials for overall water splitting and electrochemical supercapacitors. Recent advances in modification strategies are critically assessed to determine their effect on the physicochemical properties of hybrid LDHs. The hybrid nanostructures' alteration of energy barriers in the electrocatalytic reactions is also discussed. Finally, this review concludes with future outlooks for hybrid LDH nanostructures.