Hexagonal B–C–N composite consisting of <i>h</i> -BN and graphite separated by B–C nanolayer

Graphite and hexagonal boron nitride (h-BN), despite their structural similarity, exhibit opposing electronic properties, namely, metallic conductivity and wide-bandgap insulation, respectively. In recent years, graphene-h-BN heterostructures have attracted significant research interest, with the resulting hybrid B–C–N atomic-layer systems exhibiting distinctive electronic properties. Notably, interface effects play a decisive role in governing the performance of these heterostructures. Nevertheless, owing to the lack of high-quality composites, the interfacial structure in B–C–N materials and the correlation with critical properties such as charge transport and band structure modulation are not fully clear. Here, we report the direct synthesis of a millimeter-sized hexagonal B–C–N composite via a solvent method under high-pressure and high-temperature conditions. Structural characterization reveals that the synthesized B–C–N composite contains isolated graphite and h-BN. Compared with pure h-BN, the B–C–N composite has a narrower bandgap and shows a pronounced photoelectric response in the visible light region. More interestingly, we find a graphite-like B–C compound with a thickness of about 30 nm at the graphite–h-BN interface, which forms Schottky junctions with graphite, thus realizing rectification properties. Our findings provide a method for synthesizing high-quality B–C–N composites and offer new insights into the structure of the graphite–h-BN interface.