Spray pyrolytically deposited nanoporous Ti~(4+)doped hematite thin films for efficient photoelectrochemical splitting of water

摘要

Nanoporous hematite (α-Fe_2O_3) thin films doped with Ti_(4+) deposited by spray-pyrolysis were successfully used in photoelectrochemical splitting of water for solar hydrogen production. X-ray diffraction, field emission scanning electron microscopy, UV-visible absorption and photoelectrochemical studies have been performed on the undoped and Ti_(4+)doped hematite thin films. Morphology of α-Fe_2O_3 thin films was observed to be nanoporous, with increased porosity (pore size ～12 to 20 nm) on increasing doping concentration. A significant decrease in the bandgap energy from 1.95 to 1.27 eV was found due to doping.α-Fe_2O_3 film doped with 0.02 M Ti~(4+) ions exhibited best solar to hydrogen conversion efficiency (photoconversion efficiency) of 1.38% at 0.5 V/SCE. Highest photo-current densities of 0.34 mA/cm~2 at zero bias and 1.98 mA/cm~2 at 0.5 V/SCE were obtained by incorporating 0.02 M Ti~(4+)in α-Fe_2O_3, which are significantly larger than earlier reported values. Donor density (30.8 × 10~(20) cm~(-3)) and flatband potential (-1.01 V/SCE) obtained were also maximum for this sample. Hydrogen collected in 1 hr at Pt electrode with the best photoelectrode was 2.44 mL with 150 mW/cm~2 visible light source.