Light-driven water oxidation by a dye-sensitized photoanode with a chromophore/catalyst assembly on a mesoporous double-shell electrode

A mesoporous atomic layer deposition (ALD) double-shell electrode, Al₂O₃ (insulating core)//ALD ZnO|ALD TiO₂, on a fluorine-doped tin oxide (FTO) conducting substrate was explored for a photoanode assembly, FTO//Al₂O₃ (insulating core)//ALD ZnO|ALD TiO₂|-chromophore-catalyst, for light-driven water oxidation. Photocurrent densities at photoanodes based on mesoporous ALD double-shell (ALD ZnO|ALD TiO₂|) and ALD single-shell (ALD ZnO|, ALD TiO₂|) electrodes were investigated for O₂ evaluation by a generator-collector dual working electrode configuration. The high photocurrent densities obtained based on the mesoporous ALD ZnO|ALD TiO₂ photoanode for O₂ evolution arise from a significant barrier to back electron transfer (BET) by the optimized tunneling barrier in the structure with the built-in electric field at the ALD ZnO|ALD TiO₂ interface. The charge recombination is thus largely decreased. In the films, BET following injection has been investigated through kinetic nanosecond transient absorption spectra, and the results of energy band analysis are used to derive insight into the internal electronic structure of the electrodes.