Enhancing photoelectrochemical water splitting by aluminum-doped plate-like WO3 electrodes

• Al-doped plate-like WO3 films were prepared by hydrothermal method in dilute nitric acid solution from Al-W films on the FTO glass substrates.
• High photocurrent density was achieved by appropriate amount Al doped plate-like WO3 films.
• Efficient charge transfer of Al-doped WO3 plate-like electrodes led to increases of photocurrent.
• Al-doped WO3 plate-like electrodes are desirable to become a novel electrode material for water splitting.

ABSTRACTIn the present work, aluminum-doped plate-like tungsten oxide (WO3) photoelectrodes were investigated by photoelectrochemical methods in order to evaluate the possibility of their application in water splitting. The aluminum-doped plate-like WO3 films were prepared by hydrothermal method in nitric acid from a radio frequency (RF) magnetron sputtered aluminum-tungsten layer on fluorine-doped tin oxide (FTO) glass. The crystal structure, composition and morphology of pure and aluminum-doped WO3 were compared using x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results indicate that aluminum can be doped into WO3 plate-like photoelectrodes by placing radio frequency magnetron sputtered aluminum-tungsten films using a facile hydrothermal method. Plate-like WO3 films doped with 0.77 atom% aluminum showed photocurrent density of 1.14 mA/cm2 at 1.2 V vs. Ag/AgCl, which was 1.3 times higher than that of the pure WO3 (0.87 mA/cm2). Incident photon to current efficiency (IPCE) measurements carried out on photoelectrochemical (PEC) cell with aluminum-doped WO3 plate-like photoelectrodes as anodes demonstrated a significant increase of photoresponse in the intrinsic absorption range. Electrochemical impendence spectroscopy (EIS) showed that aluminum-doped WO3 possessed higher charge transfer rate and electrical conductivity than those of pristine WO3, thus presented a better performance in photoelectrochemical properties.