Work Function of Water-Exfoliated Hexagonal Boron Nitride Flakes

Abstract

Triboelectric nanogenerators (TENGs) convert mechanical stimuli into electrical energy by coupling triboelectrification with electrostatic induction at contact interfaces. A key factor governing TENG performance is the difference in work function between contact surfaces. In this study, we investigate the effect of water-based exfoliation on the work function of hexagonal boron nitride (h-BN), which is a two-dimensional material with promising triboelectric properties. We exfoliate h-BN powder in deionized water using bath sonication and subsequently drop cast it onto Si substrates to form thin films. The work functions of these films are compared with those of pristine h-BN flakes using Kelvin probe force microscopy. The drop-casted h-BN films exhibit a higher work function than the pristine flakes. Additionally, Fourier transform infrared spectroscopy shows a significant O–H stretching signal in the drop-casted films, thus indicating hydroxyl functionalization during sonication. This functionalization is likely responsible for the observed increase in work function. Furthermore, zeta-potential analysis confirms the high stability of the h-BN aqueous dispersion (zeta potential < −40 mV) and an average flake size of ~480 nm, thereby supporting its suitability for scalable and cost-effective production. These findings suggest that h-BN aqueous exfoliation not only enables the scalable and environmentally friendly processing of h-BN but also provides a route for enhancing TENG performance via surface functionalization.