Figure shows typical electrolysis i-t curves corresponding to: (A) a solution containing Ru(NH3)6 3+ and S2O8 2-and (B) a solution containing Ru(NH3)6 3+ , S2O8 2-, and C2O4 2-. In both cases, the i-t curve displays an exponential decay, with the current decreasing to zero when Ru(NH3)6 3+ and S2O8 2-are both fully reduced. Note that Ru(NH3)6 3+ is reduced to Ru(NH3)6 2+ once S2O8 2-is fully consumed by either reaction with Ru(NH3)6 2+ or via the autocatalytic reaction. We also note that in the presence of C2O4 2-, Figure , it is theoretically possible that the oxidation of CO2 •-, eq 13 and Scheme 3, may contribute to the electrolysis current, which would lower the observed cathodic current due to Ru(NH3)6 3+ and S2O8 2-reduction. However, CO2 •-is generated homogeneously away from the electrode surface as a transient species and is always present at very low concentrations (< 1 nM, vide infra, see simulated concentration profiles in Section V) and, thus, does not significantly contribute to the overall electrolysis current.