Controllable Synthesis of Mesoporous TiO₂ Hollow Shells: Toward an Efficient Photocatalyst

Abstract

TiO 2 hollow shells with well-controlled crystallinity, phase, and porosity are desirable in many applications. In photocatalysis in particular, they can provide high active surface area, reduced diffusion resistance, and improved accessibility to reactants. Here, the results from studies of the causes for the failure of a prior etching and calcination scheme to make such shells and on a newly-developed simple yet robust process for producing uniform mesoporous TiO 2 shells with precisely controllable crystallinity and phase are reported. The key fi nding is that base etching of the SiO 2 @TiO 2 coreshell particles leads to the formation of sodium titanate species, which, if not removed, promote substantial crystal growth during calcination and destroy the structural integrity of the TiO 2 shells. A simple acid treatment of the baseetched samples may convert the sodium titanates into protonated titanates, which not only prevent the formation of the impurity phases, but also help to maintain the structural integrity of the shell and allow precise control of the TiO 2 phase and crystallinity. This new development affords convenient optimization of the structure of the hollow TiO 2 shells toward effi cient photocatalysts, which outperform the commercial P25-TiO 2 in the photocatalytic decomposition of organic dye molecules.

Contribution of multiple reflections to light utilization efficiency of submicron hollow TiO2 photocatalyst

“…In addition to the intrinsic materials characteristics including low cost, low toxicity, and high chemical and optical stability [15,16], hollow nanostructures of TiO2 are believed to be able to provide a high active surface area, reduced diffusion resistance, and improved accessibility, which are beneficial features for photocatalysis. We have previously synthesized mesoporous hollow TiO2 shells with high surface areas through a surface-protected calcination process, revealed how the surface coating of another oxide or polymer could affect the crystallinity and the catalytic activity of the shells, and demonstrated that the phase composition, degree of crystallinity, surface area, and dispersity of TiO2 were important features required for photocatalysis [17][18][19][20].…”

Mesoporous Titania‐Iron(III) Oxide with Nanoscale Porosity and High Catalytic Activity for the Synthesis of β‐Amino Alcohols and Benzimidazole Derivatives

“…[7][8] These materials have been explored in gas adsorption, [9] sensing, [10] catalysis, [11] as energy storagem aterials, [12] and in biological applications. [13] Aw ide range of organic transformations that involve bulky substrate molecules, such as the epoxide ring-opening reaction, [14] acid- [15] or base-catalyzed reactions, [16] photocatalysis, [17] ands ize-and shape-selective isomerization [18] are performed very efficiently over these materials with nanoscale porosity.…”

Vacuum‐Treated Mo,S‐Doped TiO2:Gd Mesoporous Nanospheres: An Improved Visible‐Light Photocatalyst

“…As a result, a significant advancement in photocatalytic performance was obtained. Another key factor of a photocatalyst is its specific surface area, and scholars tend to synthesize mesoporous titania, [29][30][31][32][33] which thereby generates a larger reaction surface area and a stronger adsorption capacity. Metal or non-metal doping, [34][35][36] compositing, [37][38][39] hydrogenation, [40] and other means change mesoporous titania into a visible-light photocatalyst.…”