Superlattices of covalently cross-linked 2D materials for the hydrogen evolution reaction

C N R Rao,K Pramoda,Pratap Vishnoi,Abdo Hezam,Aditi Saraswat,Nidhish Sagar,Reetendra Singh

doi:10.1063/1.5135340

Abstract

Amongst the recent developments in 2D materials, van der Waals heterostructures formed by depositing a monolayer or few-layers of a 2D material on a monolayer or on few-layers of the same or another 2D material have attracted great attention. As an alternative to such heterostructures, we have carried out investigations on covalently cross-linked heterostructures by chemical coupling of layers of the same or different 2D materials. This effort has met with success, with typical systems studied by us being graphene–graphene, graphene–MoS2, C3N4–MoS2, borocarbonitride–MoS2, and phosphorene–MoS2. We describe these structures to demonstrate how the covalent cross-linking strategy yields novel 2D nanocomposites. These structures exhibit interesting gas adsorption properties as well as noteworthy hydrogen evolution reaction (HER) activity. The phosphorene–MoS2 nanocomposite is found to exhibit superior photocatalytic HER activity. The most interesting nanocomposite is BCN–MoS2 which exhibits electrochemical HER activity comparable to platinum, thus providing a new and novel example of metal-free catalysis.

Highlights

INTRODUCTIONBesides graphene[1,2] and other elemental 2D materials,[3] intense investigations have been carried out on other inorganic 2D materials such as transition metal dichalcogenides.[4,5] In particular, MoS2 has been found to exhibit many novel properties, an interesting one pertaining to the hydrogen evolution reaction (HER).[6,7] A significant development in the area of 2D materials is that of van der Waals heterostructures obtained by the stacking of different 2D structures
There has been intense research on 2D materials in the last few years
MoS2–MoS2 and MoS2–reduced graphene oxide (RGO) nanocomposites: The photocatalytic hydrogen evolution reaction (HER) activity of MoS2–MoS2 and MoS2–RGO nanocomposites has been examined in the presence of Eosin Y (EY) dye as the sensitizer and triethanolamine (TEOA) as the sacrificial electron donor, under UV–vis light illumination.[40]

Summary

INTRODUCTION

Besides graphene[1,2] and other elemental 2D materials,[3] intense investigations have been carried out on other inorganic 2D materials such as transition metal dichalcogenides.[4,5] In particular, MoS2 has been found to exhibit many novel properties, an interesting one pertaining to the hydrogen evolution reaction (HER).[6,7] A significant development in the area of 2D materials is that of van der Waals heterostructures obtained by the stacking of different 2D structures Typical of these heterostructures are graphene–MoS28 and graphene–BN.[9] Another interesting development relates to the generation of novel materials by covalent cross-linking of 2D layers.[10] Examples of these are graphene– graphene, graphene–MoS2, MoS2–C3N4, MoS2–BCN, and so on. We have given an account of the effect of the relative proportions of the two 2D layers in the nanocomposites and of the length of the linker (inter-layer gap) on the HER activity of the covalently linked 2D nanocomposites

DIFFERENT COVALENTLY CROSS-LINKED 2D MATERIALS

GAS ADSORPTION PROPERTIES IN BRIEF

HER ACTIVITY

EFFECT OF THE INTER-PLANAR SEPARATION ON HER ACTIVITY

CONCLUDING REMARKS