Replication Route Synthesis of Mesoporous Titanium-Cobalt Oxides and Their Photocatalytic Activity in the Degradation of Methyl Orange

摘要

Mesoporous Ti-Co oxides were synthesized via a replication route, using a 3-D wormlike mesoporous sil ica as template and tetra-tert-butyl orthotitanate (TBOT) and Co(NO3)2 as source materials. The prepared materials were characterized by X-ray diffraction (XRD), N2-physi-sorption, TEM, EDS, and UV/Vis-DRS and found to possess a spherical morphology and a 3-D wormhole-like mesoporous structure, with the average pore size between 4.5 and 16.0 nm. The pore walls consisted mainly of a cobalt-incorporated anatase phase. The Co~(3+) ions were generated in the replicated mesoporous Co-Ti oxides, via the transfer of electrons from Co~(2+) to Ti~(4+) ions. The formation of cobalt-incorporated anatase phase and Co~(3+) ions were both favored by larger Co/Ti atomic ratios and by relatively low calcination temperatures. The specific surface area decreased and the mesopore sizes increased, with increasing Co/Ti atomic ratio or calcination temperature. The average crystal size of the anatase phase decreased with increa ing Co/Ti atomic ratio but increased with increasing calcination temperature. The photocatalytic activity of the replicated mesoporous Co-Ti oxides in the degradation of methyl orange dye was investigated. It was observed that the photocatalytic activity increased with increasing Co/Ti atomic ratio and exhibited a maximum with increasing calcination temperature. With the exception of those prepared at too high calcination temperatures, the replicated mesoporous Co-Ti oxides were much more active than the pure titania. It is concluded that, in addition to a higher diffusion, the cobalt-containing anatase, as the active phase, and the Co~(3+) ions, as the active sites, are responsible for the high photocatalytic activity of the replicated mesoporous Co-Ti oxide.