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

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 H-1 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, N-2 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.

Automated summary

A series of composite CdS/TiO2 powders were synthesized by nucleating TiO2 on CdS nanoseeds. This composite exhibited the appropriate band edge position for photocatalytic redox reactions: visible light irradiation of CdS facilitated electron injection into TiO2, thereby extending charge lifetimes. The obtained electrons were utilized for the efficient photoreduction of 4-nitrobenzaldehyde to 4-aminobenzaldehyde, as confirmed by H-1 NMR and ESI-MS positive ion mode. Simultaneously, sacrificial oxidation of 2-propanol occurred, serving as the proton source. Characterization techniques highlighted the crucial factors driving the photocatalytic reaction, including the nanoscale anatase crystalline domains, the presence of dispersed CdS forming an extended active junction CdS/anatase, and the presence of mesopores as nanoreactors. This system not only exhibited high photocatalytic activity using visible light but also demonstrated improved stability and recyclability due to the combination of TiO2 and CdS.