Gold nanocage coupled single crystal TiO2 nanostructures for near-infrared water photolysis

Gold (Au) nanocages were deposited on single crystal TiO2 columnar thin films and their effect on the photoelectrochemical performance for water oxidation was studied. The performance was compared to spherical Au nanoparticles of similar size (30 nm) deposited on the columns to investigate the shape effect. The performance of spherical Au nanoparticles with a 5 nm diameter was also measured as an indicator of the size effect. All Au-TiO2 thin films exhibited enhanced photocurrents compared to the pristine TiO2 thin film under visible and near-infrared light irradiation. In particular, the nanocage Au deposited TiO2 thin film exhibited the maximum photocurrent, approximately 8 times higher than that by the pristine TiO2 film. Photocurrent action spectra of the thin films confirmed the role of surface plasmon resonance in the performance enhancement caused by hot electron injection into the TiO2 conduction band. Light absorption was controlled in the 520-810 nm region by change of size and shape of the Au nanoparticles. The absorption range of the nanocages in the NIR region with high photocurrent makes them promising candidates for solar water-splitting.