Herein, we show that very efficient electrochemical initiation of the S2O8 2-/C2O4 autocatalytic reaction is made possible by using an outer-sphere redox electrocatalyst, Ru(NH3)6 3+/2+ , to reduce S2O8 2-in solution. We show that the 1e -mediated reduction of S2O8 2-by electrogenerated Ru(NH3)6 2+ occurs at distances sufficiently far from the electrode surface (i.e., tens of micrometers) that the direct reduction of SO4 •-at the electrode is dramatically mitigated (and entirely eliminated under optimal conditions), thus, allowing eq 2 to proceed in initiating autocatalysis. Cyclic voltammetry is employed to investigate the mechanism and kinetics of the mediated S2O8 2-/C2O4 2-autocatalytic reaction, while controlled-potential bulk electrolysis (CPE) is used to measure the amount of electrical charge required to initiate autocatalysis. Differential electrochemical mass spectrometry (DEMS) is also used to demonstrate that the S2O8 2-/C2O4 2- autocatalytic reaction generates CO2 for ~10 minutes after the reaction is initiated, without the input of additional electrical charge. The DEMS results unequivocally demonstrate that eqs 2 and 3 represent a coupled and self-sustaining reaction pair. In-depth mechanistic analysis of the S2O8 2- /C2O4 2-autocatalytic reaction using first-principles density functional theory calculations (DFT), ab initio molecular dynamics simulations (AIMD), and finite difference (FD) simulations of the voltammetric response, support the proposed autocatalytic mechanism.