Effects of the Degree of Graphene Oxidation on the Oxidation Evolution Reaction of Lithium Peroxide: First-Principles Study

Finding graphene oxide (GO) with an optimal oxidation concentration as a catalyst for the oxygen evolution reaction (OER) associated with the decomposition of lithium peroxide (Li2O2) is of great importance for achieving high energy density and reversible lithium–air batteries. In this work, first-principles calculations were carried out to investigate the OER of Li2O2 on GO with different degrees of oxidation. Our studies show that GO enhances the interaction with Li2O2 and LiO2 molecules compared to perfect graphene. As the degree of graphene oxidation increases, the charge transferred from Li2O2 or LiO2 molecules to GOn gradually increases, resulting in a gradual shortening of O–O bond lengths and lengthening of Li–O bond lengths. The Li atoms in the Li2O2 molecule can form up to four bonds with oxygen atoms in GOn, while the Li atom in the LiO2 molecule can form up to three bonds with oxygen atoms in GOn. According to the calculated Gibbs free energy, the rate-determining step (RDS) for GO1 is the first step, while the RDS for GO2–6 is the second step. Among the six oxidation concentrations considered, GO5 and GO6 have the lowest charge overpotentials of 0.05 and 0.06 V, respectively.