Covalently Bonded MoS2–Borocarbonitride Nanocomposites Generated by Using Surface Functionalities on the Nanosheets and Their Remarkable HER Activity C

In the light of the recent discovery that carbon-rich borocarbonitrides show electrocatalytic activity for generating hydrogen from water, we have synthesized nanocomposites by covalently cross-linking BC₇N with MoS₂ sheets to explore whether the HER activity can be significantly enhanced. In order to cross-link BC₇N and MoS₂ sheets, we have exploited the presence of different functional groups on the surfaces of BN (NH₂) and graphene (COOH) domains of the borocarbonitride, as quantitatively determined by FLOSS. We have thus obtained two nanocomposites differing in the location of the cross-linking and these are designated as BN/BCN–MoS₂ and G/BCN–MoS₂, depending on which domains in the borocarbonitride participate in cross-linking. These nanocomposites were characterized by various spectroscopic methods including fluorescence labeling and their electrochemical and photochemical HER activity investigated. The composite where the graphene domains are cross-linked to MoS₂ nanosheets, G/BCN–MoS₂ (1:2), exhibits outstanding electrochemical HER activity with an onset potential of −30 mV (vs RHE) and a current density of 10 mA cm–² at an overpotential of −35 mV. This performance is closely comparable to that of Pt. The composite where the BN domains were cross-linked show somewhat lower activity. The physical mixture of BCN and MoS₂, on the other hand, does not display any notable HER activity. The BCN–MoS₂ composites also exhibit good photochemical activity. It is noteworthy that 2H-MoS₂, which does not exhibit significant catalytic activity, can be rendered highly active by cross-linking with BCN.