Adsorption properties of O2 on the unequal amounts of binary co-doped graphene by B/N and P/N: A density functional theory study

Graphene acts as an advanced substrate material, and it has been used as an electrode in fuel cells because it can efficiently adsorb oxygen molecules. In this study, density functional theory (DFT) calculation has been performed to exactly simulate the adsorption and dissociation of oxygen molecules on the XY3-co-doped graphene. The results show that the positively charged P and B atoms act as active sites for oxygen adsorption on the surface of graphene. In addition, PN3-G and NP3-G exhibit higher catalytic activity than the other samples because of the facile transfer of electrons from the highest occupied molecular orbital (HOMO) of O-2 to the orbital above the Fermi level in the samples. More interestingly, excessive adsorption leads to the direct dissociation of oxygen molecules and making further dissociation difficult In conclusion, the adsorption of oxygen molecules at the hollow sites on the PN3-G and NP3-G occurs via the formation of a triangular ring or transformation into O-2(-) is proposed as the optimal strategy because these routes are thermodynamically favorable and the associated energy barrier is low. Furthermore, after dissociation, it was found that the oxygen atoms preferably approach the P atom. This work may be useful as a reference for future experimental studies to develop effective metal-free catalysts for fuel-cell cathodes.