C2O4 2-is subsequently oxidized by the highly oxidizing SO4 •-thus generating C2O4 •-and SO4 2-(eq 15). The one-electron oxidation potential of C2O4 2-is calculated to be 0.13 V vs Ag/AgCl using an implicit water SMD solvation model, which is significantly lower than the experimental value of 1.2 V vs Ag/AgCl (eq 11). This significant difference can be attributed to the insufficient stabilization of the anionic C2O4 2-and C2O4 •-species using implicit solvation, in line with observations in our previous work for modeling highly anionic aqueous species in the reduction of S2O8 2-to S2O8 3-• . A detailed analysis showing the variation of the oxidation potentials with DFT methods, including the effect of the functionals and basis sets, is presented in the SI, and illustrates the critical role of solvation for these anionic species, irrespective of the methods.