An aqueous, organic dye derivatized SnO2/TiO2 core/shell photoanode

Visible light driven water splitting in a dye-sensitized photoelectrochemical cell (DSPEC) based on a phosphonic acid-derivatized donor-pi-acceptor (D-pi-A) organic dye (P-A-pi-D) is described with the dye anchored to an FTO| SnO2/TiO2 core/shell photoanode in a pH 7 phosphate buffer solution. Transient absorption measurements on FTO| TiO2|-[P-A-pi-D] compared to core/shell, FTO| SnO2/TiO2 (3 nm)|-[P-A-pi-D], reveal that excitation of the dye is rapid and efficient with a decrease in back electron rate by a factor of similar to 10 on the core/shell. Upon visible, 1 sun excitation (100 mW cm(-2)) of FTO| SnO2/TiO2(3 nm)|-[P-A-pi-D] in a phosphate buffer at pH 7 with 20 mM added hydroquinone (H(2)Q), photocurrents of similar to 2.5 mA cm(-2) are observed which are sustained over > 15 min photolysis periods with a current enhancement of similar to 30-fold compared to FTO vertical bar TiO2 vertical bar-[P-A-pi-D] due to the core/shell effect. On surfaces co-loaded with both -[P-A-pi-D] and the known water oxidation catalyst, Ru(bda)(pyP)(2) (pyP = pyridin-4-methyl phosphonic acid), maximum photocurrent levels of 1.4 mA cm(-2) were observed which decreased over an 10 min interval to 0.1 mA cm(-2). O-2 was measured by use of a two-electrode, collector-generator sandwich cell and was produced in low faradaic efficiencies with the majority of the oxidative photocurrent due to oxidative decomposition of the dye.