Composite CdS/TiO2 Powders for the Selective Reduction of 4-Nitrobenzaldehyde by Visible Light: Relation between Preparation, Morphology and Photocatalytic Activity

Abstract

A series of composite CdS/TiO2 powders was obtained by nucleation of TiO2 on CdS nanoseeds. This combination presents the appropriate band edge position for photocatalytic redox reactions: visible light irradiation of CdS allows the injection of electrons into dark TiO2, increasing the lifetimes of separated charges. The electrons have been used for the quantitative photoreduction of 4-nitrobenzaldehyde to 4-aminobenzaldehyde, whose formation was pointed out by 1H NMR and ESI-MS positive ion mode. Concomitant sacrificial oxidation of 2-propanol, which was also the proton source, occurred. The use of characterization techniques (XRD, N2 adsorption-desorption) evidenced the principal factors driving the photocatalytic reaction: the nanometric size of anatase crystalline domains, the presence of dispersed CdS to form an extended active junction CdS/anatase, and the presence of mesopores as nanoreactors. The result is an efficient photocatalytic system that uses visible light. In addition, the presence of TiO2 in combination with CdS improves the stability of the photoactive material, enabling its recyclability.

CdS-Based Hydrothermal Photocatalysts for Complete Reductive Dehalogenation of a Chlorinated Propionic Acid in Water by Visible Light

“…Yanagida and coworkers reported that several polychlorinated benzenes were dehalogenated using ZnS and CdS nanocrystals under UV and visible light irradiation, respectively, in the presence of triethanolamine as a sacrificial electron donor for the photogenerated holes [25]. Similar processes were studied also with CdS/TiO 2 nanocomposites, exploiting the demonstrated improvement of charge separation efficiency [26][27][28][29]. Core shell ZnSe/CdS quantum dots had been used for hydrogenation or arylation of aryl bromides under 455 nm irradiation with DIPEA (N,N diisopropylethylamine) as a sacrificial donor [30].…”

Orange peel biochar/clay/titania composites: low cost, high performance, and easy-to-reuse photocatalysts for the degradation of tetracycline in water

“…Moreover, in addition to poor activity under visible light irradiation, any large-scale application of TiO 2 nanoparticles (NPs) for water treatment is hampered by the tendency of titania NPs to agglomerate and by difficulties in NP separation after water treatment leading to poor catalyst recovery. [17][18][19][20] Consequently, numerous efforts are underway to (1) improve the photocatalytic response of TiO 2 under visible light, 21 (2) improve the ease of separation of the photocatalyst from a water body that has been treated, 22 and…”

“…Moreover, in addition to poor activity under visible light irradiation, any large-scale application of TiO 2 nanoparticles (NPs) for water treatment is hampered by the tendency of titania NPs to agglomerate and by difficulties in NP separation after water treatment leading to poor catalyst recovery. 17–20 Consequently, numerous efforts are underway to…”

A Novel Hydrothermal CdS with Enhanced Photocatalytic Activity and Photostability for Visible Light Hydrogenation of Azo Bond: Synthesis and Characterization

“…therein [ 18 ], and the use of CdS-based photocatalysts for the photocatalytic reduction of CO 2 gradually has aroused a great interest from researchers in recent years [ 19 , 20 , 21 ]. They report that there are many factors that affect the efficiency of these reductive processes, including the morphology, crystal structure and composition; in addition, the synthetic method employed plays an important role in establishing and influencing the characteristics of the obtained material [ 22 ]. More generally, the location of the conduction band at negative potentials makes CdS a photocatalyst of interest for reductive transformations that take advantage of electrons promoted in the conduction band [ 23 ].…”