RESUMO
ZnTiO3/TiO2 composite photocatalysts were synthesized via the sol-gel technique, and the impact of varying heat treatment temperatures (470, 570, 670 °C) on their crystalline arrangement, surface morphology, elemental composition, chemical state, specific surface area, optical characteristics, and photocatalytic efficacy was systematically investigated. The outcomes revealed that, as the temperature ascends, pure TiO2 undergoes a transition from anatase to rutile, ultimately forming a hybrid crystal structure at 670 °C. The incorporation of ZnTiO3 engenders a reduction in the TiO2 grain dimensions and retards the anatase-to-rutile phase transition. Consequently, the specimens manifest a composite constitution of anatase and ZnTiO3. In contrast, for pure TiO2, the specimen subjected to 670 °C annealing demonstrates superior photocatalytic performance due to its amalgamated crystal arrangement. The degradation efficacy of methylene blue (MB) aqueous solution attains 91% within a 60-min interval, with a calculated first-order reaction rate constant of 0.039 min-1. Interestingly, the ZnTiO3/TiO2 composite photocatalysts exhibit diminished photocatalytic activity in comparison to pristine TiO2 across all three temperature variations. Elucidation of the photocatalytic mechanism underscores that ZnTiO3 coupling augments the generation of photogenerated charge carriers. Nonetheless, concurrently, it undermines the crystalline integrity of the composite, yielding an excess of amorphous constituents that impede the mobility of photoinduced carriers. This dual effect also fosters escalated recombination of photogenerated charges, culminating in diminished quantum efficiency and reduced photocatalytic performance.
RESUMO
In this study, pure CeO2 and oxygen-vacancy-enriched SnO2-CeO2 composite materials were prepared using the sol-gel method, and their microstructures and photocatalytic properties were investigated. The results indicate that SnO2 coupling promotes the separation and transfer of photogenerated electrons and holes and suppresses their recombination. The 50% SnO2-CeO2 composite material exhibited a decreased specific surface area compared to pure CeO2 but significantly increased oxygen vacancy content, demonstrating the highest photogenerated charge separation efficiency and the best photocatalytic performance. After 120 min of illumination, the degradation degree of MB by the 50% SnO2-CeO2 composite material increased from 28.8% for pure CeO2 to 90.8%, and the first-order reaction rate constant increased from 0.002 min-1 to 0.019 min-1.
Assuntos
Elétrons , Iluminação , OxigênioRESUMO
Pure and Ag/AgCl-modified titania powders with anatase/rutile/brookite three-phase mixed structure were prepared by one-step hydrothermal method. The effects of Ag/Ti atomic percentages on the structure and photocatalytic performance of TiO2 were investigated. The results showed that pure TiO2 consisted of three phases, anatase, rutile, and brookite, and that Ag addition promoted the transformation from anatase to rutile. When the molar ratio of Ag/Ti reached 4%, the AgCl phase appeared. The addition of Ag had little effect on the optical absorption of TiO2; however, it did favor the separation of photogenerated electrons and holes. The results of photocatalytic experiments showed that after Ag addition, the degradation degree of rhodamine B (RhB) was enhanced. When the molar ratio of Ag/Ti was 4%, Ag/AgCl-modified TiO2 exhibited the highest activity, and the first-order reaction rate constant was 1.67 times higher than that of pure TiO2.
RESUMO
The anatase/rutile mixed crystal TiO2 was prepared and modified with Ag decoration and SnO2 coupling to construct a Ag@SnO2/anatase/rutile composite photocatalytic material. The crystal structure, morphology, element valence, optical properties and surface area were characterized, and the effects of Ag decoration and SnO2 coupling on the structure and photocatalytic properties of TiO2 were studied. Ag decoration and SnO2 coupling are beneficial to reduce the recombination of photogenerated electrons and holes. When the two modification are combined, a synergistic effect is produced in suppressing the photogenerated charge recombination, making Ag@SnO2/TiO2 exhibits the highest quantum utilization. After 30 min of illumination, the degradation degree of tetracycline hydrochloride (TC) by pure TiO2 increased from 63.3% to 83.1% with Ag@SnO2/TiO2.
RESUMO
Using butyl titanate and absolute ethanol as raw materials, TiO2 was prepared by a hydrothermal method with different hydrothermal times, and the influences of hydrothermal time on the structure and photocatalytic performance of TiO2 were investigated. The obtained samples were characterized by XRD, SEM, TEM, BET, PL and DRS, separately. The results show that TiO2 forms anatase when the hydrothermal time is 12 h, forms a mixed crystal composed of anatase and rutile when the hydrothermal time is 24 h, and forms rutile when the hydrothermal time is 36 h. With the extension of hydrothermal time, anatase gradually transforms into rutile and the surface area decreases. Although TiO2-24 h and TiO2-36 h show lower photoinduced charge recombination and higher light source utilization, TiO2-12 h exhibits the highest photocatalytic activity owing to its largest surface area (145.3 m2/g). The degradation degree of rhodamine B and tetracycline hydrochloride reach 99.6% and 90.0% after 45 min.
