Facile one-step and high-yield synthesis of few-layered and hierarchically porous boron nitride nanosheets

Abstract

Few-layered boron nitride nanosheets (BNNSs) have attracted increasing research interest in the past few years due to their unique material properties. However, the lack of a reliable scale-up production method is an inhibiting issue for their practical applications. In this work, we report a facile one-step and high-yield method for the synthesis of few-layered and hierarchically porous BNNSs through simultaneous etching and in situ nitridation of calcium hexaboride (CaB₆) by ammonium chloride under moderate conditions. The output of the few-layered BNNSs is as high as 1.4 g with respect to 1.06 g of starting CaB₆ crystals. Transmission electron microscopy and atomic force microscopy characterizations confirm the successful synthesis of few-layered BNNSs, most of which are layered with a thickness less than 3 nm (layer number < 10). The as-prepared BNNSs exhibit a high specific surface area (492–795 m² g⁻¹) and a high pore volume (0.34–0.50 cm³ g⁻¹). In addition, the as-resulted BNNSs exhibit high and tuneable H₂ uptakes from 1.48 to 2.18 wt% at 77 K and at a relatively low pressure of 1.0 MPa, thus guiding the further search of materials for H₂ storage. Our results suggest that the simultaneous etching and in situ nitridation of metallic borides is a facile and effective method for reliable production of few-layered BNNSs with hierarchical porosity for potential applications such as gas storage and functional composites.