Effects of hydronium intercalation and cation substitution on the photocatalytic performance of layered titanium oxide Original Research Article

We have investigated the effects of hydronium (H3O+) intercalation and transition metal substitution on the photocatalytic activity of layered titanate. The basal spacings of the cesium titanate and Fe-/Ni-substituted titanates are notably expanded by 1 M HCl treatment, indicating the intercalation of hydronium ion. Diffuse reflectance UV–vis spectroscopic results clearly demonstrate that, in contrast to the hydronium intercalation, the substitution of transition metal ions gives rise to a remarkable narrowing of bandgap energy down to ∼1.9–2.3 eV. According to Fe K- and Ni K-edge X-ray absorption spectroscopic analysis, the substituted iron and nickel ions are stabilized in octahedral titanium sites with trivalent and divalent oxidation states, respectively. The photodegradation tests for organic dye molecules reveal that the hydronium intercalation enhances remarkably the photocatalytic performance of cesium titanate under UV irradiation and the substitution of Fe or Ni endows wide bandgap titanate with visible light driven photocatalytic activity.