Low thermal conductivity of 2D borocarbonitride nanosheets

Two-dimensional (2D) borocarbonitrides (BCN) are of interest since their electrical and optical properties can be tuned for renewable energy applications. Although there have been theoretical studies, experimental studies of the thermal transport and thermoelectric properties of BCN nanosheets have not yet been explored. We have synthesized few-layer BCN nanosheets of different compositions, and characterized them by Raman spectroscopy, X-ray photoelectron spectroscopy and transmission electron microscopy (TEM). They exhibit p-type semiconducting thermoelectric transport properties in 300–573 ​K range. More interestingly, the BCN nanosheets exhibit low thermal conductivity (0.58–1.86 ​W/mK) unlike boron nitride (h-BN) and graphene over the temperature range of 300–573 ​K. The low thermal conductivity of BCN nanosheets arises due to significant phonon scattering by the different length scale hierarchical nano/meso architectures such as bonding heterogeneity (e.g. C–B, C–N and B–N), point defects related C/B/N disorder, nanodomains of BN/carbon and grain boundaries.