Physical and photoelectrochemical properties of the ilmenite NiTiO 3 prepared by wet chemical method and its application for O 2 evolution under visible light

Abstract The ilmenite NiTiO 3 prepared by wet chemical method is characterized by thermal gravimetry (TG), X-ray diffraction (XRD), FTIR and Scanning Electron Microscopy (SEM). The oxide crystallizes in the hexagonal symmetry with grains size in the range [200–300 nm]. The BET analysis gives a specific surface area of ~ 4 m 2  g −1 . The UV–vis diffuse reflectance analysis gives a direct transition at 2.57 eV well matched to the solar spectrum. The transport properties exhibit n -type semiconductor with an activation energy of 0.11 eV and an electron mobility of 5.82 × 10 −4  cm 2  V −1  s −1 . The physical and chemical characterizations are correlated for the construction of the energy diagram in order to assess the photoelectrochemical properties for the oxygen evolution. The valence band, deriving from O 2- : 2p orbital (2.19 V SCE ), is located above the O 2 /H 2 O potential (~ 1.5 V SCE ), allowing O 2 -evolution upon visible light (15 mW cm −2 ) and the oxide is photocathodically protected against corrosion. An evolution rate of 0.046 mL mg −1  h −1 is obtained within 20 min upon visible light and under optimal conditions (200 mg of catalyst, pH ~ 3 and 50 °C).