Mesoporous Ti–Co oxides were synthesized via a replication route, using a 3-D wormlike mesoporous silica 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-physisorption, 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 Co3+ ions were generated in the replicated mesoporous Co–Ti oxides, via the transfer of electrons from Co2+ to Ti4+ ions. The formation of cobalt-incorporated anatase phase and Co3+ 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 increasing 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 Co3+ ions, as the active sites, are responsible for the high photocatalytic activity of the replicated mesoporous Co–Ti oxide.
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We are grateful to the financial support from the Program for New Century Excellent Talents in University, the Ministry of Education of P. R. China; and the Program for Lotus Scholar in Hunan Province, P. R. China.