Gold Nanorod-Enhanced Light Absorption and Photoelectrochemical Performance of α-Fe2O3 Thin-Film Electrode for Solar Water Splitting

Surface plasmon-enhanced light absorption for photoelectrochemical water splitting at alpha-Fe2O3 thin film electrode coated with Au nanorods (NRs) is described. Au NRs are self-assembled onto a hematite thin film electrode using electrostatic force between their positively charged cetyltrimethylammonium bromide (CTAB) layer and negatively charged hematite surface functionalized with poly(4-styrenesulfonate). The photoelectrochemical reaction of the plasmon active substrate for water oxidation reaction is performed and compared at various hematite layer thicknesses. When the alpha-Fe2O3 electrode is biased at a small potential +0.2 V (vs Ag/AgCl), the photocurrent of water oxidation is reduced because of increased recombination of holes and electrons at the surface of the Au NRs. When the bias potential is increased to +0.5 V (vs Ag/AgCl), a plasmon enhancement of the photoelectrochemical reaction of water oxidation at wavelengths near the plasmon resonance condition is observed at the alpha-Fe2O3 thin film electrodes accompanying a dramatic increase in the background current. The significant increase in photocurrent in the region of surface plasmon absorption is attributed to the enhanced visible light absorption of alpha-Fe2O3 in the presence of the plasmon active Au NRs.