Evaluation of sol–gel TiO2 photocatalysts modified with carbon or boron compounds and crystallized in nitrogen or air atmospheres

• We study diphenhydramine degradation under near ultraviolet–visible light.
• TiO2 photocatalysts crystallized under air atmosphere are the most active.
• The highest conversion rates are observed for TiO2 modified with boric acid.
• The efficiencies of sol–gel TiO2 are comparable or even higher than reference P25.
• The best photocatalysts possess anatase:rutile ratios in excess of 95%.

Sol–gel TiO2 photocatalysts are synthesized from titanium isopropoxide and crystallized by thermal treatment under either air atmosphere or nitrogen flow. Reference TiO2 photocatalysts crystallized at 550 °C for 30 min in air are the most active for the degradation of diphenhydramine pharmaceutical (DPH). In addition, TiO2 precursors are modified with carbon or boron compounds. The highest rates of conversion are obtained in the case of TiO2 modified with boric acid and crystallized in air. The sol–gel photocatalysts with the best performances possess anatase:rutile phase ratios in excess of 95% with anatase crystallites of approximately 60 nm. The photocatalysts are characterized by different solid state and solution techniques, including powder X-ray diffraction, elemental analysis, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, diffuse reflectance ultraviolet–visible (UV–Vis), UV–Vis liquid spectroscopy, surface area analysis and ammonia thermal programmed desorption. The efficiencies of the synthetized photocatalysts are characterized by the kinetics of DPH degradation under near UV–Vis irradiation. The efficiencies of the synthetized photocatalysts are comparable or even higher than that of the reference P25, although their dispersions in water have much lower absorbance values.

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