Ordered mesoporous C/TiO₂ composites as advanced sonocatalysts

Ordered mesoporous C/TiO₂ composites have been fabricated via an evaporation induced co-assembly method, and demonstrated as a highly efficient sonocatalyst. The effects of the carbon content in the composites and calcination temperature have been investigated thoroughly in this work and optimized for the production of well-defined mesoporous C/TiO₂ materials. The resultant composites possess superior "brick-mortar" frameworks with uniform TiO₂ nanocrystals glued by a carbon matrix, and exhibit highly ordered mesostructures with high surface area (∼200 m² g^-1). More importantly, the mesoporous C/TiO₂ composites show a high sonocatalytic degradation rate of Rhodamine B. The maximum pseudo-first-order reaction rate constant obtained with the composites 15C-85TiO₂-450 (C: 15.2 wt%, TiO₂: 84.8 wt%, calcined at 450 °C) is 0.178 min^-1, which is 2.7 and 4.8 times higher than that of P25 (0.062 min^-1) and ultrasound (0.037 min^-1) alone, respectively. The excellent sonocatalytic performance is a result of fast mass diffusion, enhanced nucleation rate and rapid surface hydroxyl radical oxidation. In addition, the recycling test shows that the sonocatalytic degradation rate with 15C-85TiO₂-450 is retained even after five cycles, which is related to the well-retained mesostructure with superior mechanical stability. We believe that the present results provide important insights into the design and synthesis of advanced sonocatalysts.