The influence of the anatase nanoparticles boundaries on the titania activity performance

• Interactions of amorphous and crystalline phases modify catalysts properties.
• Amorphous phases of catalysts strongly affect their activity performance.
• Amorphous TiO2 favors the nanocrystals self-assembling but hinders their growth.
• Amorphous TiO2 boundaries hamper inter-particles transport of electrons.

Metal oxides structures, formed by ordered self-assembling of crystalline nanoparticles aggregates, are attracting growing attention in fields such as catalysis or solar cells. The properties of these structures are influenced not only by their morphology and nanoparticles composition but also by the assembled particles boundaries. In order to determine the influence of these boundaries on the structures properties, the present investigation has been devoted to study the characteristics of anatase nanoparticles boundaries in titania aggregates prepared by TiCl4 hydrolysis at low temperature. Proton magic angle spinning nuclear magnetic resonance and high resolution transmission electron microscopy show that these samples mainly contain amorphous TiO2 strongly bound to specific faces of anatase particles. This amorphous titania-mediated attachment induces the ordered self-assembling of the anatase particles, with favored formation of mesopores in the nanoparticles boundaries. Photocatalytic degradation of 4-methoxybenzyl alcohol in water, test reaction used as a method to get information on the boundaries properties, indicates that the mesoporous amorphous TiO2 offers active sites for the alcohol catalytic partial oxidation, but it strongly hampers inter-particles electron transfer. These effects, characteristic of amorphous oxide chain morphology, can be expected when low dispersed dopants or promoters are incorporated to metal oxides.

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