Ge-doped hematite nanosheets with tunable doping level, structure and improved photoelectrochemical performance

Doping impurities and nanostructuring are two effective ways to modulate the photoelectrochemical properties of hematite materials. Ge-doped hematite (alpha-Fe2O3) nanocrystals were synthesized by combining laser ablation in liquid and hydrothermal synthesis. The doping level of Ge and morphology of hematite could be readily tuned through adjusting the ablation time. Hematite nanocrystals doped with 2 at% Ge exhibited a morphology of ultra-thin circular nanosheets with a thickness of about 10 nm and diameter of 200 nm, while hematite doped with 5 at.% Ge consisted of assembled nanosheets with a thickness of about 30-40 nm. High-resolution transmission electron microscopy demonstrated that Ge presented randomly at the Fe sites in the hematite lattice of the 2 at% doped hematite, but at a higher doping level of 5 at%, Ge distributed orderly in the host lattice to result in doubling of the basal plane vector. The band gap of alpha-Fe2O3 can be reduced by Ge doping, leading to increased photocurrent density and improvement in the photoelectrochemical performance of alpha-Fe2O3. (C) 2013 Elsevier Ltd. All rights reserved.