Ultra-low thermal conductivity, high thermoelectric figures of merit and high photocatalytic activity of monolayer Ag(2-x)CuxS (x = 0, 1, 2)

Abstract

2D materials simultaneously with excellent thermoelectric performance and high photocatalytic activity have attracted considerable attention due to their potential applications in clean renewable energy sources. In this article, we proposed three 2D materials, namely Ag2S, Cu2S and AgCuS, respectively, in which Ag2S and AgCuS are auxetic materials with negative Poisson’s ratios of −0.11 and −0.06. Moreover, the monolayers possess both high thermal and kinetic stability, and show band gaps of 2.77 eV, 1.79 eV and 2.11 eV, respectively. Also, due to the strong anharmonic effects, the monolayers exhibit ultra-low lattice thermal conductivities of 0.44–1.43 W·m−1·K−1, resulting in high thermoelectric figures of merit of 0.28–0.84 at 300 K, and even 0.82–2.42 at 500 K. In addition, the monolayers also show high photocatalytic water splitting activity, which can photocatalyze water to produce H2, O2, etc. All of these characteristics indicate that they have promising applications in clean energy such as thermoelectric materials and photocatalytic devices.