Photocatalytic performance of alumina-incorporated titania composite nanoparticles: Surface area and crystallinity Original Research Article

Alumina-incorporated titania (AIT) nanoparticles, a TiO2-based binary photocatalyst with tunable Al/Ti ratio, can be prepared via an one-pot non-aqueous synthetic route. The adjustable Al/Ti atomic ratio (from 4.4% to 11.85%) offers a needed opportunity to elucidate the optimal incorporation level for AIT to attain the maximum photocatalytic efficiency, and to study the effect of incorporated alumina on the crystallinity of the nanocomposite photocatalyst. The nanoparticles with highest Al/Ti ratio (AIT-4, Al/Ti = 11.85%) reveal the largest specific surface area (SSA) of 370.89 m2 g−1, which is 4.7% larger than that of the one with lowest Al/Ti ratio (AIT-7, Al/Ti = 4.4%, 353.66 m2 g−1). Nevertheless, AIT-4 is about seven times larger than Degussa P25 (53.25 m2 g−1) in SSA. The phase composition of AIT was monitored by powder X-ray diffraction (P-XRD). The gradual changes in composition of nanoparticle and surface area accompanying crystallinity were evaluated by EDX of HR-TEM and by BET analysis. The characterization data show that the crystallinity of AIT photocatalysts decreases as the atomic ratio of Al/Ti increases from 4.4% to 11.85%. In the photocatalytic degradation of salicylic acid (SA) by UV lamp (λ = 254 nm, 18 W), the degradation rate constants of SA over P25 (0.0057 min−1), AIT-4 (0.0142 min−1), AIT-6 (Al/Ti = 7.88%, 0.0158 min−1), and AIT-7 (0.0173 min−1) are in the ratio of 0.33:0.82:0.91:1.00. The experimental data show that the highest catalytic efficiency is achieved with the sample having the lowest SSA (i.e. AIT-7). Therefore, the optimal incorporation amount of Al2O3 in AIT is Al/Ti = 4.4%, suggesting that the effects of crystallinity prevail over those of the surface area, when the difference of SSA among the photocatalysts is less than 5%.