Photocatalytic oxidation of aniline over MO/TiO2 (M = Mg, Ca, Sr, Ba) under visible light irradiation

Magnetically Separable Visible Light-Active Ag0.75Ni0.25 Binary Alloy Nanoparticles as a Highly Efficient Photocatalyst for the Selective Oxidative Coupling of Aniline to Azobenzene

Aniline wastes can be converted to useful pharmaceutical and industrial compounds like azobenzene. For this purpose, a bimetallic Ag_0.75Ni_0.25 alloy is designed in the nanoscale range resembling a fivefold twinned morphology using water as the solvent. These newly developed alloy nanoparticles (NPs) are employed for the first time as an efficient visible light-active photocatalyst for the oxidative homocoupling of aniline to azobenzene. Our catalytic protocol is highly sustainable for a large number of aniline substrates with a high yield of the product (up to 95%), which might be attributed to the combinational and superior properties achieved on alloy formation in comparison to the monometallic counterparts. High-electron density amines (p-anisidine) display greater photocatalytic proficiency than that of low-electron density amines (4-fluoroaniline). The developed photocatalyst is magnetically well-separable and can be reused for at least five catalytic cycles without appreciable loss in its activity.

Selective aqueous oxidation of aromatic alcohols under solar light in the presence of TiO2 modified with different metal species

A set of metals modified TiO₂ photocatalysts were prepared starting from titanium tetraisopropoxyde and different metal precursors to study the influence of the addition of the various foreign agents on the physico-chemical and photocatalytic properties of the catalysts. The powders were characterized by X-ray diffraction, Raman spectroscopy, specific surface area measurements, scanning electron microscopy, energy dispersive X-ray spectroscopy, UV-Vis diffuse reflectance spectroscopy, photoluminescence, temperature programmed desorption after CO₂ adsorption. The photocatalytic activity was evaluated using as probe reactions the partial oxidation of three aromatic alcohols: benzyl alcohol (BA), 4-methoxy benzyl alcohol (4-MBA), and 4-hydroxy benzyl alcohol (4-HBA) under simulated solar light irradiation. Different oxidation and selectivity values were obtained for the three substrates depending not only on the type of metals but also on the nature and position of the substituent in the phenyl ring of benzyl alcohol. As a general behaviour, the doped samples allowed the achievement of a greater selectivity especially for 4-MBA even if sometimes with minor conversions. The presence of W or Nb was beneficial for both conversion and selectivity for all the substrates with respect to bare TiO₂.

Co-embedding oxygen vacancy and copper particles into titanium-based oxides (TiO2, BaTiO3, and SrTiO3) nanoassembly for enhanced CO2 photoreduction through surface/interface synergy

Photocatalytic CO₂ reduction into valuable fuel and chemical production has been regarded as a prospective strategy for tackling with the issues of the increasing of greenhouse gases and shortage of sustainable energy. A composite photocatalysis system employing a semiconductor enriched with oxygen vacancy and coupled with metallic cocatalyst can facilitate charge separation and transfer electrons. In this work, mesoporous TiO₂ and titanium-based perovskite oxides (BaTiO₃ and SrTiO₃) nanoparticle assembly incorporated with abundant oxygen vacancy and copper particles have been successfully synthesized for CO₂ photoreduction. As an example, the TiO₂ decorated with different amounts of Cu particles has an impact on photocatalytic CO₂ reduction into CH₄ and CO. Particularly, the optimal TiO₂/Cu-0.1 exhibits nearly 13.5 times higher CH₄ yield (22.27 μmol g^-1 h^-1) than that of pristine TiO₂ (1.65 μmol g^-1 h^-1). The as-obtained BaTiO₃/Cu-0.1 and SrTiO₃/Cu-0.1 also show enhanced CH₄ yields towards photocatalytic CO₂ reduction compared with pristine ones. Based on the temperature programmed desorption (TPD) and photo/electrochemical measurements, the co-embedding of Cu particles and abundant oxygen vacancy into the titanium-based oxides could promote CO₂ adsorption capacity as well as separation and transfer of photoinduced electron-hole pairs, and finally result in efficient CO₂ photoreduction upon the TiO₂/Cu, SrTiO₃/Cu, and BaTiO₃/Cu composites.

Mineralization of High-Concentration Aqueous Aniline by Hybrid Process

The efficient mineralization of high-concentration aqueous aniline (HCAA) is an issue needing to be resolved. In this study, a hybrid process of ozonation and electrochemical oxidation (ECO) was proposed for improving the mineralization of HCAA (1000 mg·L−1). The results indicated that chemical oxygen demand (COD) removal by the hybrid process was far greater than that of a single ozonation or ECO process, revealing that the hybrid process might avoid low efficiency in late ozonation and initial ECO. Thus, a subsequent combination effect clearly existed. In this hybrid process, ozonation stage time was selected as 60 min for optimal COD removal. The main products of the ozonation stage were maleic and succinic acids, with declining pH which was beneficial to the following ECO stage. Nitrite and nitrate formed during ozonation, which acted as electrolytes for the ECO stage, in which maleic and succinic acids were fully degraded and pH thus increased. Moreover, the aniline degradation mechanism of the hybrid process was deduced, demonstrating the superiority of this hybrid process. Finally, more than 95% COD removal was achieved, which met the COD limit requirement and achieved pH control simultaneously, according to the discharge standards of water pollutants for dyeing and finishing of the textile industry in China (GB 4287–2012).

Ultrathin ZnTi-LDH nanosheets for photocatalytic aerobic oxidation of aniline based on coordination activation

Aniline is chemisorbed and activated on ultrathin ZnTi-LDH nanosheets, facilitating the photocatalytic aerobic oxidation of aniline under visible light.