Borocarbonitrides

Borocarbonitrides are two-dimensional compounds that contain boron, nitrogen, and carbon atoms in a ratio BxCyNz.^[1][2] Borocarbonitrides are distinct from B,N co-doped graphene in that the former contains separate boron nitride and graphene domains as well as rings with B-C, B-N, C-N, and C-C bonds.^[3] These compounds generally have a high surface area, but borocarbonitrides synthesized from a high surface area carbon material, urea, and boric acid tend to have the highest surface areas.^[1][4][5] This high surface area coupled with the presence of Stone-Wales defects in the structure of borocarbonitrides also allows for high absorption of CO₂ and CH_4, which may make borocarbonitride compounds a useful material in sequestering these gases_.^[1][4]

Electrical

The band gap of borocarbonitrides range from 1.0–3.9eV^[1] and is dependent on the content of the carbon and boron nitride domains as they have different electrical properties.^[1] Borocarbonitrides with a high carbon content have lower bandgaps^[2] whereas those with higher content of boron nitride domains have higher band gaps.^[1] Borocarbonitrides synthesized in gas or solid reactions also tend to have large bandgaps and are more insulating in character.^[1] The wide range of composition of boronitrides allows for the tuning of the bandgap, which when coupled with its high surface area and Stone-Wales defects may make boronitrides a promising material in electrical devices.^[2][6]

Synthesis

Solid state reaction

A high surface area carbon material such as activated charcoal, boric acid, and urea are mixed together and then heated at high temperatures to synthesize borocarbonitride.^[2] The composition of the resulting compounds may be changed by varying the concentration of the reagents as well as the temperature.^[1]

Gas phase synthesis

In chemical vapor deposition, boron, nitrogen, and carbon precursors react at high heat and are deposited onto a metal substrate.^[1] Varying the concentration of precursors and the selection of certain precursors will give different ratios of boron, nitrogen, and carbon in the resulting borocarbonitride compound.^[2]

Borocarbonitride composites

Borocarbonitride can also be synthesized by random stacking of boronitride and graphene domains through covalent interactions^[2] or through liquid interactions.^[1] In the first method, graphene and boron nitride sheets are functionalized and then are reacted to form layers of borocarbonitride.^[2] In the second method, boron nitride and graphite powder are dissolved in isopropanol and dimethylformamide, respectively, and then sonicated.^[2] This is then exfoliated to isolate borocarbonitride layers.

References