The DEMS methodology also provides a direct demonstration of the self-sustaining nature of the autocatalytic reaction, as suggested in Scheme 3. In the experiment corresponding to Figure , the ionic current associated with CO2 + (m/z = 44) generation was monitored during and following a single CV cycle in which the electrode potential was cycled between 0.1 and -0.5 V, and then back to 0.1 V, where it was held constant. As shown in Figure , at a scan rate of 20 mV/s, the CO2 + signal initially exhibits a rapid increase on the negative scan direction upon reduction of Ru(NH3)6 3+ until the potential reaches -0.22 V, corresponding approximately to the peak potential for Ru(NH3)6 3+ reduction. The CO2 + signal then slowly decreases due to the consumption of C2O4 2-and reduced generation of CO2 near the carbon cloth electrode. However, as shown later in Section V, the autocatalytic reaction continues to propagate through the solution, continuing to generate CO2 at distances further from the electrode and DEMS sample inlet. After completion of the CV scan and while the electrode potential was held at 0.1 V, CO2 + remained detectable for an additional ~600 s before decaying to the background level. These results demonstrate that CO2 is continuously generated and can be detected for at least ~10 minutes following cessation of the Ru(NH3)6 2+ -catalyzed reduction of S2O8 2-. Similar results were observed at both 10 mV/s and 5 mV/s, Figure . These results directly demonstrate that the S2O8 2- /C2O4 2-autocatalytic reaction is self-sustaining, once initiated by generation of a finite quantity of S2O8