Titanium-embedded layered double hydroxides as highly efficient water oxidation photocatalysts under visible light

Here, we have synthesized the new titanium-embedded layered double hydroxides (LDHs), such as (Ni/Ti)LDH and (Cu/Ti)LDH. First of all, the formation of LDH structures and the bonding nature for a mixed oxide structure of LDHs are explored in this work. Also, it is determined that our LDHs show two absorption bands in the red and blue regions under visible light, thus different from those of a pure titanium oxide with absorption bands in only the UV region. We find that the (Ni/Ti)LDH with the high surface area showed a higher reaction rate, producing 49 μmol O2 in water oxidation by using 200 mg of the photocatalyst and 1 mmol of AgNO3 as a sacrificial agent. Also, the (Cu/Ti)LDH showed a good reaction rate and produced 31 μmol of O2 under the same condition. On the other hand, conventional TiO2 nanoparticles generated a very small amount of oxygen within the error range under this visible light irradiation. Consequently, these results imply that absorption bands in the visible range and the large surface area of an LDH could result in the high water oxidation photocatalytic activity under visible light.