Square-Octagon Structure of a BCN Monolayer: Near-Zero Poisson’s Ratio, High Carrier Mobility, and Excellent Photocatalytic Activity for Overall Water Splitting

Abstract

We predicted a square-octagon structure of a BCN monolayer with fantastic mechanical properties, high carrier mobility, and excellent photocatalytic activity for overall water splitting. The BCN monolayer has unique mechanical properties with a very small negative value of Poisson’s ratio of −0.0058 and −0.0045 along the x- and y-direction, respectively, and remarkable flexibility under tensile strain. The electronic structure calculation suggests that the BCN monolayer has a direct bandgap of 2.82 eV and its band edges straddle the redox potentials for H+/H2 and O2/H2O. Additionally, the BCN monolayer exhibits a high intrinsic conductivity with an exceptional high hole mobility of ∼2.8 × 105 cm2 V–1 s–1. The drastically different mobilities of electrons and holes in the BCN monolayer may reduce the rate of electron–hole recombination, resulting in improved photocatalytic activity. With excellent stability, ideal band edge positions, high conductivity, and efficient visible-light absorption, the BCN monolayer well satisfies the strict requirements for ideal photocatalytic overall water splitting. The unique mechanical and electronic properties of the BCN monolayer also make it an attractive material for use in advanced nanomechanical and electronic devices.