Plasmon-enhanced photocatalytic activity of iron oxide on gold nanopillars.

Photocatalytic water splitting represents a promising way to produce renewable hydrogen fuel from solar energy. Ultrathin semiconductor electrodes for water splitting are of particular interest because the optical absorption occurs in the region where photogenerated charge carriers can effectively contribute to the chemical reactions on the surface. It is therefore important to manipulate and concentrate the incident light so that more photons can be absorbed within the thin film. Here we show an enhanced photocurrent in a thin-film iron oxide photoanode coated on arrays of Au nanopillars. The enhancement can be attributed primarily to the increased optical absorption originating from both surface plasmon resonances and photonic-mode light trapping in the nanostructured topography. The resonances can be tuned to a desirable wavelength by varying the thickness of the iron oxide layer. A net enhancement as high as 50% was observed over the solar spectrum.