V vs Ag/AgCl (i.e., at a potential corresponding to diffusion-limited Ru(NH3)6 3+ reduction). The Ag/AgCl reference electrode was placed in the cathode compartment, which contained 24 mL of solution. The anode compartment contained a graphite rod counter electrode (~50 cm 2 ) immersed in 20 mL of a 0.1 M Na2SO4 solution (pH = 6.8), separated from the cathode compartment by a porous glass frit and a permeable ion exchange membrane made of 3 M KCl solution in agar. A detailed description of the cell and electrolysis procedure is discussed in the Supporting Information.