Covalent Functionalization of Antimonene and Bismuthene Nanosheets.

Antimonene and bismuthene are promising members of the 2D pnictogen family with their tunable band gaps, high electronic conductivity, and ambient stability, making them suitable for electronic and optoelectronic applications. However, semi-metal to semiconductor transition occurs only in the mono/bilayer regime, limiting their applications. Covalent functionalization is a versatile method for tuning materials' chemical, electronic, and optical properties and can be explored for tuning the properties of pnictogens. In this work, emissions in liquid exfoliated antimonene and bismuthene are observed at ≈2.23 and ≈2.33 eV, respectively. Covalent functionalization of antimonene and bismuthene with p-nitrobenzene diazonium salt proceeds with the transfer of lone pairs from Sb/Bi to the diazonium salt, introducing organic moieties on the surface attached predominantly via Sb/BiC bonds. Consequently, Sb/Bi signatures in Raman and X-ray photoelectron spectra are blue-shifted, implying lattice distortion and charge transfer. Interestingly, emission can be tailored upon functionalization to 2.18 and 2.27 eV for antimonene and bismuthene respectively, and this opens the possibility of tuning the properties of pnictogens and related materials. This is the first report on covalent functionalization of antimonene and bismuthene. It sheds light on the reaction mechanism on pnictogen surfaces and demonstrates tunability of optical property and surface passivation.

Borocarbonitrides as Metal-Free Catalysts for the Hydrogen Evolution Reaction.

Hydrogen generation by water splitting is clearly a predominant and essential strategy to tackle the problems related to renewable energy. In this context, the discovery of proper catalysts for electrochemical and photochemical water splitting assumes great importance. There is also a serious intent to eliminate platinum and other noble metal catalysts. To replace Pt by a non-metallic catalyst with desirable characteristics is a challenge. Borocarbonitrides, (Bx Cy Nz ) which constitutes a new class of 2D material, offer great promise as non-metallic catalysts because of the easy tunability of bandgap, surface area, and other electronic properties with variation in composition. Recently, Bx Cy Nz composites with excellent electrochemical and photochemical hydrogen generation activities have been found, especially noteworthy being the observation that Bx Cy Nz with a carbon-rich composition or its nanocomposites with MoS2 come close to Pt in electrocatalytic properties, showing equally good photochemical activity.