The Special Activity of Stone–Wales Defect Graphene for the Oxygen Reduction Reaction: A Comparison Study between the Charge-Neutral Model and the Constant Potential Model Calculated by Density Functional Theory

This study investigates the difference of Stone–Wales defect graphene on the oxygen reduction reaction (ORR) under the charge-neutral model (CNM) and the constant potential model (CPM) using density functional theory (DFT). Under the CPM, two methods, the double reference method (DRM) and grand-canonical density functional theory (GC-DFT), are used. The calculated limiting potential is 0.854 V under the CNM. The limiting potential calculated by the DRM decreases first and then increases with an increase in pH. The limiting potential calculated by GC-DFT increases with pH increasing, and another limiting potential appears at pH ≥ 5, which means that the Gibbs free energies for each step are all smaller than 0 only at a certain potential range (between the two limiting potentials). These results broke the scaling relation and volcano plot obtained under the CNM. The different limiting potential or activity under the CNM and the CPM can be primarily attributed to the position of the surface Van Hove singularity (SVHS); the farther away it is from the Fermi level, the lower is the limiting potential. Microkinetic simulation was performed to obtain the turnover frequency (TOF) for H2O and the coverage of *O and *OH changed with the applied potential. The half-wave potential calculated under the CNM or GC-DFT is equal to the corresponding limiting potential. However, the half-wave potential calculated by the DRM at pH = 0 is larger than the calculated limiting potential, which indicates an unneglected kinetic effect.