Investigation of the initial reactions of lithium oxides on the graphitic carbon nitrides (g-C3N4) for catalyst in non-aqueous lithium - air batteries: A first-principles calculations

Highlights: •Investigation on the possibility of g-C₃N₄ as catalyst for LiO₂ batteries. •Overpotential of Heptazine was remarkable and comparable to the Triazine. •Overpotential difference was related to the adsorption energy (E_ads) of LiO₂. •Hybridization between Li and bound N on Heptazine is weaker than Triazine. •Hybridization between Li and bound N was a key factor of E_ads. -- Abstract: The catalytic mechanism of the initial reaction of lithium oxides formation on buckled graphitic carbon nitrides (g-C₃N₄) as a catalyst for non-aqueous Li–O₂ batteries was investigated using density function theory. The overpotential of heptazine were superior to triazine and precious metal. It was revealed that the difference in overpotential between heptazine and triazine was mainly a result of the gap of charge voltages. Using potential-dependent surface phase diagram, it was confirmed that the charge voltage was determined by the LiO₂ formation. The hybridization of Li and bound N in the cavity revealed a clear distinction between substrates. Through the charge analysis, these results stemmed from the electron difference of bound N that was caused by the cavity structural property depending on the substrates. These findings may provide insight for designing of N-doped carbon materials as catalysts for Li–O₂ batteries, which possess overpotential that are lower than existing catalyst materials.