Enhanced Water Splitting on Thin-film Hematite Photoanodes Functionalized with Lithographically Fabricated Au Nanoparticles

Iron oxide in its crystalline form (hematite, alpha-Fe2O3) is an interesting candidate as a photoanode material for photoelectrochemical cells, in spite of its non-optimal optoelectronic properties. We report here on the beneficial effect of Au nanodisks on the photocurrent of alpha-Fe2O3. Photoanodes consisting of ultra-thin alpha-Fe2O3 films lithographically functionalized with Au nanodisks of varying size were characterized and tested. We found a significant increase in photocurrent for the functionalized samples. The highest increase in incident photon-to-electron conversion efficiency is roughly one order of magnitude compared with a reference sample without Au nanodisks and was found for incident light of 420 nm in wavelength. A detailed understanding of the phenomena underlying such an increase in efficiency is crucial to fully exploit the beneficial effect of the metallic nanostructures. This would contribute to make Fe2O3 more competitive in the race for the development of a commercially viable device for water splitting.