Borocarbonitrides, BxCyNz, 2D nanocomposites with novel properties

Abstract

Chemical doping of graphene is necessary to generate a band gap that is valuable for a range of applications. Chemical doping of graphene with elements like nitrogen and boron gives rise to useful properties. In this context, recent studies of borocarbonitrides, BxCyNz, comprising carbon, and the two elements on either side of it, are of significance. While uniformly homogeneous compositions of borocarbonitrides may be hard to generate, there have been efforts to synthesize them by solid state as well as gas phase routes. The products obtained show evidence for the presence of B-C and C-N bonds besides B-N and C-C bonds (but no N-N bonds), and possible occurrence of random BCN networks in addition to graphene and BN domains. Properties of borocarbonitrides depend on the composition, and the method of synthesis, enabling one to traverse from the insulating BN to the conducting graphene. In this account, we present important features of borocarbonitrides including synthesis, characterization, properties and potential applications. Surface oxygen functionalities and amine-groups of borocarbonitrides have been quantitatively determined by the fluorescence labeling of surface species (FLOSS) technique. Typical applications are in gas adsorption and energy devices such as supercapacitors and fuel cells as well as electrochemical sensors. Performance of borocarbonitrides as a HER catalysts is impressive, showing electrochemical activity close to that of Pt. It is possible to covalently link a BCN layer to other 2D nanosheets and the materials obtained by such cross-linking with layers of C3N4, MoS2 and MoSe2 show outstanding HER performance and other useful characteristics. Interestingly, heterostructures of BCN with nanosheets of MoS2 and other 2D materials can be formed reversibly by supramolecular means, which show good visible-light driven photochemical hydrogen evolution activity.