Highly enhanced photocatalytic activity of nanotubular Fe2O3/Fe2WO6 nanocomposite film formed by anodizing FeW alloy

This study demonstrates the highly enhanced photocatalytic activity of Fe2O3 nanotubes by making a hetero-junction with Fe2WO6 and doping of W6+ ions into the alpha-Fe2O3 phase for water splitting and decomposition of an organic pollutant. Both nanotubular and compact Fe2O3/Fe2WO6 films are formed by anodizing the magnetron -sputtered Fe-9 at% W alloy in fluoride-containing ethylene glycol electrolyte and subsequent annealing at 450 degrees C. Their photocatalytic activities are compared with W-free nanoporous Fe2O3 film formed on high-purity Fe. The nanotubular Fe2O3/Fe2WO6 film exhibits a markedly enhanced photoelectrochemical oxygen evolution reaction and photocatalytic degradation of methylene blue compared with the nanoporous W-free Fe2O3 film. Because of the larger surface area, the nanotubular Fe2O3/Fe2WO6 film reveals further increased activity than the compact Fe2O3/Fe2WO6 film. The STEM study discloses the dispersion of Fe2WO6 nanoparticles in the alpha-Fe2O3 phase after annealing at 450 degrees C, and XRD analysis shows the possible doping of W species into alpha-Fe2O3. The formation of the W-doped alpha-Fe2O3/Fe2WO6 heterojunction likely promotes the separation of photogenerated electron-hole pairs, enhancing photocatalytic activity. Hence, the nanotubular Fe2O3/Fe2WO6 film is a possible candidate for visible-light-driven photocatalysts.