Effect of Ce:Ti ratio and cerium salts on the properties of mesoporous Ti-Ce oxides and their photocatalytic activity

Abstract

To investigate the influence of different CeO₂ precursors and Ce:Ti ratios, we have synthesised 8 mesoporous Ti-Ce oxides via the evaporation-induced self-assembly (EISA) method with Ce:Ti ratios between 0.2 and 20 mol%. The materials exhibited type IV isotherms and a specific surface area of 140–180 m²·g⁻¹ with pore diameters in range of 3–20 nm. The crystalline phases of materials comprised predominantly anatase with a significant decrease in overall crystalline content with increasing Ce:Ti ratio. Materials with higher Ce:Ti ratio showed an increased light absorption in the visible region. Although crystalline CeO₂ was not detected, the presence of Ce(IV) was confirmed by X-ray photoelectron spectroscopy. For the photocatalytic experiments, we compared these materials with the TiO₂-CeO₂ composites of our previously published syntheses to yield 16 samples synthesized via three synthesis approaches: (1) concurrent synthesis from titanium alkoxide and cerium salts in one pot, (2) synthesis of TiO₂ in the presence of previously-synthesised CeO₂ and (3) physical mixing of separately-synthesised TiO₂ and CeO₂. Samples produced by physically mixing the separately-synthesised TiO₂ and CeO₂ showed the best photocatalytic activity towards gaseous isopropanol degradation, while the samples with TiO₂ synthesised in the presence of CeO₂ showed the best photocatalytic stability.