Silver-loaded nitrogen-doped yolk–shell mesoporous TiO₂hollow microspheres with enhanced visible light photocatalytic activity

Abstract

Silver-loaded nitrogen-doped yolk-shell mesoporous TiO2 hollow microspheres (Ag-N-TiO2-YSM) were prepared by employing acetic acid as the hollowing controller and triethanolamine as the N source for the first time. Ag nanoparticles (NPs) were uniformly deposited by a simple in situ photo-reduction method, which can prevent the aggregation of Ag NPs. The efficiency of the as-prepared samples was investigated by monitoring the degradation of rhodamine B and ciprofloxacin under visible light irradiation. The experimental results indicate that N-doped yolk-shell mesoporous TiO2 hollow microspheres show higher photocatalytic activity than P25 TiO2 under visible light irradiation because of N doping and the unique yolk-shell structure. In addition, Ag-N-TiO2-YSM shows enhanced activity compared with N-TiO2-YSM due to the SPR absorption of silver NPs and the fast generation, separation and transportation of the photogenerated carriers. Moreover, the Ag contents can affect the photocatalytic activity of the Ag-N-TiO2-YSM composite. A suitable amount of Ag deposition gives the highest photocatalytic activity. A higher loading does not improve the photocatalytic activity of N-TiO2-YSM further. The active species generated in the photocatalytic system were also investigated. Based on our experimental results, a possible photocatalytic mechanism was proposed. The strategy presented here gives a promising route towards the development of delicate metal@hollow semiconductor composites for many applications in photocatalysis.

Hollow TiO2 microspheres assembled with rutile mesocrystals: Low-temperature one-pot synthesis and the photocatalytic performance

“…The microspheres were anatase TiO 2 , which exhibited high photocatalytic activity; yet they were fabricated by a hydrothermal route, which costs more for a scale-up production when compared with the present non-hydrothermal technique. A hollow structure also contributes to the photocatalytic activity [31,32]. Therefore, the rutile mesocrystal hollow microspheres synthesized in the current investigation can find potential application in wastewater treatments.…”

Preparation and visible light responsive photocatalytic activity of Fe3O4/Ni-Al-Ce LDH/Bi2WO6 composites

“…In addition, the first-order reaction rate equations are shown in Table 2, indicating that the photocatalytic process of MO decolorization conforms to first-order kinetics. 38,39 From Table 2, we find that the reaction rate constant decreased as the methyl orange concentration increased. As is well-know, physical interpretation of reaction rate constant is reaction rate of unit concentration (1 mol L -1 ).…”

“…44 This process is beneficial for separating the photogeneration electron-hole pairs and prolonging the lifetime of the charge carriers. 45,46 The electrons on the Bi 2 WO 6 surface can react with dissolved oxygen to form superoxide radicals, owing to its more negative CB position. 20 In addition, the process of the photocatalytic reaction can generate strong oxidative species, such as •OH, H 2 O 2 and O 3 .…”

A simple green approach to synthesis of sub-100 nm carbon spheres as template for TiO2 hollow nanospheres with enhanced photocatalytic activities

“…Compared with their solid counterparts, hollow TiO 2 nanoparticles (NPs) with porous walls have been intensively explored due to their enlarged surface areas, reduced densities and enhanced photocatalytic activity [3][4][5][6][7]. Considerable efforts have been made in preparing TiO 2 hollow nanostructures [7][8][9][10][11].…”

“…For the fabrication of TiO 2 shells, different templating approaches using hard or soft templates [8,[12][13][14], layer-by-layer coating or emulsion/interfacial polymerization [15,16] have been successfully demonstrated in past years. In comparison to organic surfactants as soft templates, hard templates (such as polymer microspheres [7], metal (Au, Ag, Pt) colloid beads [5,17,18], and silica spheres) could generate hollow TiO 2 nanostructures [19] with controllable monodispersity and size. However, the hard templating methods mentioned above usually inevitably introduce different organic reagents serving as surfactants or catalysts, and strong oxidative reagents for precious metal corrosion.…”