Yeob Lee

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.

Efficient Co–Fe layered double hydroxide photocatalysts for water oxidation under visible light

We report new Co–Fe LDH water oxidation photocatalysts and their water oxidation abilities under visible light with different ratios of transition metals. The layered structure containing more iron displayed the highest efficiency, attributed to good crystallinity, enhanced light absorbance and low charge carrier recombination of Co–O–Fe oxo-bridges.

Graphitic domain layered titania nanotube arrays for separation and shuttling of solar-driven electrons

Herein, we report a facile method for synthesizing graphitic carbon domains of thin island shapes on the surfaces of titania nanotubes, which were prepared by using hydrothermal and pyrolytic treatments with glucose. The faster decay time of the solar-driven electrons and the lower charge transport resistance on carbon domains as compared to those in the case of bare titania nanotubes serve to increase the solar-to-hydrogen conversion rate.