文摘
We report CF<sub>3sub>-substituted porphyrins and evaluate their use as photosensitizers in water-splitting dye-sensitized photoelectrochemical cells (WS-DSPECs) by characterizing interfacial electron transfer on metal oxide surfaces. By using (CF<sub>3sub>)<sub>2sub>C<sub>6sub>H<sub>3sub> instead of C<sub>6sub>F<sub>5sub> substituents at the meso positions, we obtain the desired high potentials while avoiding the sensitivity of C<sub>6sub>F<sub>5sub> substituents to nucleophilic substitution, a process that limits the types of synthetic reactions that can be used. Both the number of CF<sub>3sub> groups and the central metal tune the ground and excited-state potentials. A pair of porphyrins bearing carboxylic acids as anchoring groups were deposited on SnO<sub>2sub> and TiO<sub>2sub> surfaces, and the interfacial charge-injection and charge-recombination kinetics were characterized by using a combination of computational modeling, terahertz measurements, and transient absorption spectroscopy. We find that both free-base and metalated porphyrins inject into SnO<sub>2sub> and that recombination is slower for the latter case. These findings demonstrate that (CF<sub>3sub>)<sub>2sub>C<sub>6sub>H<sub>3sub>-substituted porphyrins are promising photosensitizers for use in WS-DSPECs.