A novel approach to making composite photocatalyst by peroxide sol–gel deposition of TiO2 on Al2O3 and ZrO2 nanosheets

Abstract

Photocatalysts are promising materials for removing organic dyes from the environment. TiO₂ is one of the most extensively studied photocatalysts; however, its application in the photocatalytic industry has yet to be realized. We contend that fundamental research and the quest for synergy are essential in this field. One approach to enhancing the efficiency of TiO₂ is deposition onto porous inert substrates. In this work, we introduce a novel approach by applying TiO₂ onto the surfaces of porous nanosized Al₂O₃ and ZrO₂. Employing two soft chemistry methods — the glycol-citrate route for creating a porous and inert substrate and the peroxide route for depositing a TiO₂ layer — we have created a technology that allows us to vary the TiO₂ concentration on the inert matrix. The developed composite photocatalysts demonstrate competitive efficacy in disintegrating the model dye methylene blue. The most effective photocatalyst was Al₂O₃@TiO₂ (0.26 wt.%) at 1200 °C. This material degrades approximately 98.2% of the methylene blue in 5 h, while nanosized TiO₂ degrades only 33.5% of the dye under the same conditions. The photocatalytic activity of the material is affected by the concentration of TiO₂ in the material due to the dilution of the peroxide solution. Notably, a decrease in the TiO₂ concentration enhances the photocatalytic activity of the composite. We assumed that titanium dioxide was distributed in thinner layers at lower concentrations, which increased the area of effective contact and photocatalytic activity. The most efficient aluminum and zirconium oxides decorated with titanium dioxide had surface areas of 12.7 and 16.9 m²/g, respectively, while Al₂O₃ and ZrO₂ had surface areas of 31.7 and 34.3 m²/g, respectively. Therefore, the decrease in methylene blue concentration was caused by photocatalysis but not by the sorption mechanism. The decomposition of methylene blue in all the samples is consistent with a pseudo-second-order photocatalysis model. The findings of this work lie in the precise application of TiO₂ onto the surfaces of inert matrices, which is valuable for developing photocatalytic materials.

Graphical Abstract