Lastly, we note that the finite-difference simulations of the concentration profiles of reactants (S2O8 2-and C2O4 2-) and products (SO4 2-and CO2) as a function of time strongly indicates that the S2O8 2-/C2O4 2-autocatalytic reaction shown in Scheme 4 results in a chemical traveling wave that, once initiated, propagates away from the electrode at a nearly constant velocity. For example, Figure shows simulated CV concentration profiles for S2O8 2-(black curves) and SO4 2- (blue curves) for a solution containing 0.54 mM Ru(NH3)6 3+ , 1.0 mM S2O8 2-, and 220 mM C2O4 at a scan rate of 100 mV/s. As before, the CV was started at E = 0.10 V vs Ag/AgCl and was scanned at 100 mV/s in the negative reduction to reduce Ru(NH3)6 3+ . The solid lines represent concentration profiles obtained at the switching potential (-0.50 V), while the dashed lines correspond to the concentration profiles ~6 s later at the end of the CV, when the electrode potential had returned to 0.10 V. The dashed lines clearly show that S2O8 2-is fully consumed at distances up to 150 µm from the electrode surface at the end of the CV. The simulations were continued for an additional 6 seconds, resulting in S2O8 2-and SO4 2-profiles that have essentially the same shape as at the end of the CV, but now shifted an additional ~100 µm from the surface.