Synthesis, characterization, surface properties and energy device characterstics of 2D borocarbonitrides, (BN)xC1−x, covalently cross-linked with sheets of other 2D materials

Covalent cross-linking of 2D structures such as graphene, MoS2 and C3N4 using coupling reactions affords the generation of novel materials with new or improved properties. These covalently cross-linked structures provide the counter point to the van der Waals heterostructures, with an entirely different set of features and potential applications. In this article, we describe the materials obtained by bonding borocarbonitride (BCN) layers with BCN layers as well as with other layered structures such as MoS2 and C3N4. While cross-linking BCN layers with other 2D sheets, we have exploited the existence of different surface functional groups on the graphene (COOH) and BN(NH2) domains of the borocarbonitrides as quantitatively determined by FLOSS. Hence, we have thus obtained two different BCN–BCN assemblies differing in the location of the cross-linking and these are designated as GG/BCN–BCN and GBN/BCN–BCN, depending on which domains of the BCN are involved in cross-linking. In this study, we have determined the surface areas and CO2 and H2 adsorption properties of the cross-linked structures of two borocarbonitride compositions, (BN)0.75C0.25 and (BN)0.3C0.7. We have also studied their supercapacitor characteristics and photochemical catalytic activity for hydrogen generation. The study reveals that the covalently cross-linked BCN–BCN and BCN–MoS2 assemblies exhibit increased surface areas and superior supercapacitor performance. The BCN composite with MoS2 also shows high photochemical HER activity besides electrochemical HER activity comparable to Pt. This observation is significant since MoS2 in the nanocomposite is in the 2H form. The present study demonstrates the novelty of this new class of materials generated by cross-linking of 2D sheets of inorganic graphene analogues and their potential applications.