A graphite oxide (GO) semiconductor photocatalyst with an apparent bandgap of 2.4–4.3 eV is synthesized by a modified Hummers' procedure. The as‐synthesized GO photocatalyst has an interlayer spacing of 0.42 nm because of its moderate oxidation level. Under irradiation with UV or visible light, this GO photocatalyst steadily catalyzes H2 generation from a 20 vol % aqueous methanol solution and pure water. As the GO sheets extensively disperse in water, a cocatalyst is not required for H2 generation over the GO photocatalyst. During photocatalytic reaction, the GO loses some oxygen functional groups, leading to bandgap reduction and increased conductivity. This structural variation does not affect the stable H2 generation over the GO. The encouraging results presented in this study demonstrate the potential of graphitic materials as a medium for water splitting under solar illumination.

Nitrogen-doped graphene oxide quantum dots exhibit both p- and n-type conductivities and catalyze overall water-splitting under visible-light irradiation. The quantum dots contain p-n type photochemical diodes, in which the carbon sp(2) clusters serve as the interfacial junction. The active sites for H2 and O2 evolution are the p- and n-domains, respectively, and the reaction mimics biological photosynthesis.

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We demonstrated that nanotubes synthesized from a NaOH treatment on TiO 2 with subsequent acid washing could proceed with repeatable crystalline-structure transformation through a simple acid-base washing step. By providing the unit cell parameters, we identified a divalent salt titanate (Na 2 Ti 2 O 5 ‚ H 2 O) with a layered structure as the structure formed after the NaOH treatment. With the increase in acidity during the post-treatment acid washing, the layered titaniate transformed into a nanotube through Na + -H + substitution, and eventually transformed into anatase TiO 2 . Crystalline-structure analysis has shown the feasibility of this titanate-titania transformation occuring through a simple structural rearrangement. A complete scheme for the formation and transformation of nanotubes induced by the NaOH treatment and the post-treatment washing was proposed.

Titania nanotube aggregates with different porosities were prepared from hydrothermal treatment on commercial TiO 2 particles in NaOH followed by HCl washing. Pore structure analysis reflects that pores of smaller sizes are mainly contributed by the nanotubes while those of larger sizes are contributed by the interspace region of the aggregates. The hydrothermal treatment temperature, ranging within 110-150 °C, was shown to affect not only the extent of particle-to-sheet conversion, and thus the resulting structures of the nanotubes, but also the anatase-to-rutile transformation at high temperatures. The surface area of the nanotube aggregates increases with the treatment temperature to reach a maximum of ca. 400 m 2 /g at 130 °C, and then decreases with further increase of the temperature. In HCl washing, both the charge-removal rate and final state of the electrostatic charges on TiO 2 affect the rolling of TiO 2 sheets into nanotubes. This demonstrates that the nanotube structure can be regulated by adjusting the washing condition. Selective catalytic reduction of NO with NH 3 has been conducted to prove that the vast surface of the nanotube aggregates is accessible to the interacting molecules.