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, AlO (insulating core)//ALD ZnO|ALD TiO, on a fluorine-doped tin oxide (FTO) conducting substrate was explored for a photoanode assembly, FTO//AlO (insulating core)//ALD ZnO|ALD TiO|-chromophore-catalyst, for light-driven water oxidation. Photocurrent densities at photoanodes based on mesoporous ALD double-shell (ALD ZnO|ALD TiO|) and ALD single-shell (ALD ZnO|, ALD TiO|) electrodes were investigated for O evaluation by a generator-collector dual working electrode configuration. The high photocurrent densities obtained based on the mesoporous ALD ZnO|ALD TiO photoanode for O 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 TiO 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.