Synthesis of Highly Active Heterostructured Al2TiO5/TiO2 Photocatalyst in a Neutral Medium

Abstract

In this work, heterostructured catalyst Al2TiO5/TiO2 (ATO/Ti) was synthesized by a two-step method: low-temperature sol-gel process along with hydrothermal treatment in a neutral medium. Characteristics of the fabricated catalyst were analyzed by various techniques including X-ray diffraction, Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller adsorption, UV-Vis diffuse reflectance spectroscopy, energy-dispersive X-ray spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and the point of zero charges. The content of ATO strongly affected the activity of ATO/Ti catalysts for photocatalytic degradation of cinnamic acid (CA). The catalyst, in which 33% TiO2 was replaced by ATO (33ATO/Ti), exhibited the highest activity for the removal of CA. Compared with the bare titanium oxide synthesized in water (TiO2(w)) as well as Al2TiO5 (ATO), the hybrid 33ATO/Ti catalyst exhibited the enhanced photocatalytic activity in the CA degradation under ultraviolet light. The enhancement in the catalytic activity of ATO/Ti could be related to the increase of the specific surface area and the reduction of bandgap energy obtained from the hybridization of TiO2(w) and ATO. The factors as the catalyst dosage ( $C_{\text{cat}}$ ), the airflow rate ( $Q_{\text{air}}$ ), and the solution initial pH (pH) affected the CA removal efficiency were studied on 33ATO/Ti catalyst. The optimum condition for photodegradation efficiency of CA was found to be at $C_{\text{cat}}=0.75\text{g}{\text{L}}^{-1}$ , $Q_{\text{air}}=0.3\text{Lmi}{\text{n}}^{-1}$ , and $\text{pH}=3.8$ . The highest 60-minute removal efficiency of CA reached 77.1% on 33ATO/Ti compared with 67.1% and 30.4% on TiO2(w) and on ATO, respectively. The recyclability of the 33ATO/Ti was also measured at the optimal parameters. The results showed that, compared with TiO2, the hybrid catalyst was easier to recover and reuse, and its activity decreased by 35% after 6 continuous cycles.