Sn self-doped α-Fe2O3 nanobranch arrays supported on a transparent, conductive SnO2 trunk to improve photoelectrochemical water oxidation

Abstract

We produced hierarchically branched Fe2O3 nanorods on a Sb:SnO2 transparent conducting oxide (TCO) nanobelt structure as photoanodes for photoelectrochemical water splitting. Single-crystalline SnO2 nanobelts (NBs) surrounded by Fe2O3 nanorods (NRs) were synthesized by thermal evaporation, then underwent chemical bath deposition and annealing. When Fe2O3 was crystallized by annealing, Sn was diffused from SnO2 NBs and incorporated to Fe2O3 NRs, which was confirmed through Energy dispersive spectroscopy. Unlike previous high temperature sintering (similar to 800 degrees C), Sn doped hematite NRs were obtained at a low temperature (similar to 650 degrees C). This occurred since SnO2 NBs directly connected to Fe2O3 NRs are an abundant source of Sn dopant. The 3D hematite NRs on SnO(2)NBs annealed at 650 degrees C produce a photocurrent density of 0.88 mA/cm(2) at 1.23 V vs. RHE, which is 3 times higher than that of hematite NRs on a fluorine doped tin oxide (FTO) glass substrate annealed at the same temperature. The enhanced photocurrent is attributed to the improved electrical conductivity of Fe2O3 NRs by Sn doping, the efficient electron transport pathway by TCO nanowire and the increased surface area by hierarchically branched structure.