(a) The process of POD-like catalytic reaction on pyridinic N-doped model graphene. (b) Energy profile for POD-like reactions on three types of N-doped model graphene sheets. (c) The optimized structures of graphitic N, pyridinic N, and pyrrolic N models and the corresponding reaction energies of the key endothermic step 3. (d) Difference charge densities of H2O adsorption on the oxidation-state intermediate 3 (isosurface value is 0.008 e Å-3). The blue and yellow regions indicate the depletion and the accumulation of electronic charge, respectively.