Mesoporous TiO2 thin films sensitized to visible light with [Ru(dtb)2(dcb)]2+, where dtb is 4,4′-((CH3)3C)2-2,2′-bipyridine and dcb is 4,4′-(CO2H)2-2,2′-bipyridine, abbreviated TiO2|Ru, were investigated in acetonitrile electrolytes that contained 0.1 M Na+, Li+, Mg2+, or Ca2+ perchlorate solutions with the electron donor trip-tolylamine (TPTA) or phenothiazine (PTZ). Pulsed 532 nm light excitation of TiO2|Ru with >25 mM donor concentrations quantitatively yielded TiO2(e–)|Ru + D+, and the corresponding recombination reaction between the injected electrons and the oxidized donors was monitored on nanosecond and longer time scales. The recombination kinetics were nonexponential, but were well described by the Kohlrausch–Williams–Watts stretched exponential function. For the TPTA donor, the abstracted rate constants followed the trend Na+ > Li+ > Mg2+ > Ca2+. A similar trend was seen for PTZ, although no significant difference in the recombination kinetics for Na and Li was observed, Na+ ∼ Li+ > Mg2+ > Ca2+...