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

Abstract

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(NO 3 ) 2 as source materials. The prepared materials were characterized by X-ray diffraction (XRD), N 2 -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 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 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 Co 3? ions, as the active sites, are responsible for the high photocatalytic activity of the replicated mesoporous Co-Ti oxide.

Solar simulated hydrogen evolution using cobalt oxide nanoclusters deposited on titanium dioxide mesoporous materials prepared by evaporation induced self-assembly process

“…These researchers noted that phase of TiO 2 also has a dramatic effect on photocatalytic water-splitting with anatase producing more hydrogen compared to rutile. Doping and/or surface modification of titania with cobalt ions have been studied for photocatalytic degradation of organics and dyes [14,17,18,20,21,25,44,45]. The results in general indicate that doping with cobalt ions is either detrimental to photocatalytic activity or that there is an optimal loading at which the activity of the Co-doped titania is enhanced compared to nonmodified titania.…”