Ni-Doped Overlayer Hematite Nanotube: A Highly Photoactive Architecture for Utilization of Visible Light

To efficiently transform absorbed photons to chemical energy is highly desired for the full utilization of visible light in solar hydrogen generation process. Here, a highly active photoanode consisting of a thin NixFe2-xO3 overlayer on the surface of hematite nanotube has been constructed to raise the utilization of the photoexcited carriers by Fe2O3 in the visible spectrum. We find that the obtained overlayer photoanodes promote the charge migration of photogenerated carriers to the surface, accelerating surface oxygen evolution and avoiding low energy photoexcited holes recombination at the semiconductor-liquid junction. Relative to the pristine Fe2O3 photoanodes, a sustainably high incident photon to electron conversion efficiency from 40% at 400 nm until 10% at 500 nm is observed for Ni-doped overlayer hematite, yielding similar to 280% enhancement of the photoconversion efficiency. Our results provide some guidance for the future design and optimization for the structure of photoanode.