Bifunctional 2D Superlattice Electrocatalysts of Layered Double Hydroxide-Transition Metal Dichalcogenide Active for Overall Water Splitting

Abstract

Bifunctional 2D superlattice electrocatalysts of alternating layered double hydroxide (LDH)-transition metal dichalcogenide (TMD) heterolayers were synthesized by inter stratification of the exfoliated nanosheets. Density functional theory calculations predict an increased inter-facial charge transfer between interstratified LDH and TMD nanosheets, which would lead to enhanced electrocatalytic activity. The electrostatically driven self-assembly of oppositely charged 2D building blocks, i.e., exfoliated Ni-Al-LDH/Ni-Fe-LDH and MoS, nanosheets, yields mesoporous heterolayered Ni-Al-LDH-MoS2/Ni-Fe-LDH-MoS2 superlattices. The synthesized superlattices show improved electro-catalytic activity with enhanced durability for oxygen and hydrogen evolution reactions and water splitting. The interstratification improves the chemical stability of LDH in acidic media, thus expanding its possible applications. The high electrocatalytic activity of the superlattices may be attributed to an enhanced affinity for OH-/H+, improved electrical conduction and charge transfer, and the increase of active sites. This study indicates that the formation of superlattices via self-assembly of 2D nanosheets provides useful methodology to explore high-performance electrocatalysts with improved stability.