Photoelectrochemical properties and photocatalytic activity of nitrogen-doped nanoporous WO3 photoelectrodes under visible light

In the present work, nitrogen-doped tungsten oxide (WO3) nanoporous photoelectrode was studied by photoelectrochemical and photocatalytic methods in order to evaluate the photoactivity and the possibility of its application in solar photocatalysis. WO3 nanoporous photoelectrodes were prepared by anodization of tungsten foil in NH4F/(NH4)2SO4 electrolytes, followed by annealing in NH3/N2 to incorporate N as a dopant. The crystal structure, composition and morphology of pure and nitrogen doped WO3 were compared using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM). The results indicate that nitrogen can be doped successfully into WO3 nanoporous photoelectrodes by controlling annealing temperature. Incident photon to current efficiency measurements carried out on PEC cell with N-doped WO3 nanoporous photoelectrodes as anodes demonstrate a significant increase of photoresponse in the visible region compared to undoped WO3 nanoporous photoelectrodes prepared at similar conditions. In particular, the photocatalytic and photoelectrocatalytic activity under visible light irradiation for newly synthesized N-doped WO3 nanoporous photoelectrodes were investigated by degradation of methyl orange. The photoelectrocatalytic activity of N-doped WO3 nanoporous photoelectrodes was 1.8-fold enhancement compared with pure WO3 nanoporous photoelectrodes.