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

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.