Manipulation of structural and electronic properties of B-doped carbon nano-onions based on DFT modelling

First-principle density-functional theory calculations were performed to study the effects of boron doping on carbon nano-onions (B-CNOs) with different numbers of layers. We examined numerous structures with an increasing boron content (of up to 5%) including two distribution patterns: a random distribution and a cluster formation. We found that systems with clusters are more stable than those with a random boron distribution. For the largest B-CNOs with the highest doping content, the formation of an amorphous-like structure of a boron cluster is evident. Therefore, we postulate the existence of boron clusters in real systems. In addition, by introducing different boron contents into CNOs, we also analysed their electronic properties. It was demonstrated that the boron substitution pattern is less affected by the position of the boron states within the entire electronic structure for systems with small boron clusters. For the largest B-CNOs, we found some considerable differences in the positions of the B states and the Fermi level, as well as the character of the frontier orbitals. This suggests that doped CNOs with boron clusters may also have different electrochemical properties than those with a random boron distribution.