Molecular Water Oxidation Catalysis: Characterization of Subnanosecond Processes and Ruthenium “Green Dimer” Formation

Dye-sensitized photoelectrochemical cells were prepared with popular ruthenium sensitizer (RuP) and catalyst (RuCAT) coadsorbed on mesoporous titania. The studied in 0.1 M Na2SO4(aq) by spectroscopic methods, including femtosecond transient absorption spectroscopy. formation of RuCAT dimer can be observed the naked eye due to change color from dark-red green. displays a characteristic feature λmax ≈ 670–680 nm its was found accelerated upon irradiation. Electron injection RuP into titania occurs partially excited singlet state decaying ultrafast time scale (<0.2 ps) triplet constant several tens ps. decay takes place main component about 1 quenching oxidized electron transfer is 150–200 ps independent excitation fluence. This fast first step oxidation further explains chronoamperometry data recorded for photoanodes made RuCAT. Finally, solution shows remarkable short lifetime state, longest 20