Carbon-deposited TiO₂ 3D inverse opal photocatalysts: Visible-light photocatalytic activity and enhanced activity in a viscous solution

We for the first time demonstrated carbon-deposited TiO₂ inverse opal (C-TiO₂ IO) structures as highly efficient visible photocatalysts. The carbon deposition proceeded via high-temperature pyrolysis of phloroglucinol/formaldehyde resol, which had been coated onto the TiO ₂ IO structures. Carbon deposition formed a carbon layer and doped the TiO₂ interface, which synergistically enhanced visible-light absorption. We directly measured the visible-light photocatalytic activity by constructing solar cells comprising the C-TiO₂ IO electrode. Photocatalytic degradation of organic dyes in a solution was also evaluated. Photocatalytic dye degradation under visible light was only observed in the presence of the C-TiO₂ IO sample and was increased with the content of carbon deposition. The IO structures could be readily decorated with TiO ₂ nanoparticles to increase the surface area and enhance the photocatalytic activity. Notably, the photocatalytic reaction was found to proceed in a viscous polymeric solution. A comparison of the mesoporous TiO ₂ structure and the IO TiO₂ structure revealed that the latter performed better as the solution viscosity increased. This result was attributed to facile diffusion into the fully connected and low-tortuosity macropore network of the IO structure.