Preparation and Application of Nb2O5 Nanofibers in CO2 Photoconversion.

Increasing global warming due to NOx, CO2, and CH4, is significantly harming ecosystems and life worldwide. One promising methodology is converting pollutants into valuable chemicals via photocatalytic processes (by reusable photocatalysts). In this context, the present work aimed to produce a Nb2O5 photocatalyst nanofiber system by electrospinning to convert CO2. Based on the collected data, the calcination at 600 ∘C for 2 h resulted in the best condition to obtain nanofibers with homogeneous surfaces and an average diameter of 84 nm. As a result, the Nb2O5 nanofibers converted CO2 mostly into CO and CH4, reaching values around 8.5 µmol g-1 and 0.55 µmol g-1, respectively.

Zinc oxide pieces obtained by pressing and slip casting: physical, structural and photocatalytic properties.

Photocatalysis is a promising alternative for the decontamination of effluents. In this paper, immobilized ZnO-based photocatalysts were obtained by pressing and by slip casting. The cylindrical pieces were heat-treated at 800°C. The samples were characterized by the method based on the principle of Archimedes, XRD, FTIR, Raman, diffuse reflectance and SEM. The samples obtained by slip casting presented lower apparent density (3.12 ± 0.04 g/cm3), higher apparent porosity (44.87 ± 0.47%) and smaller grain size (0.48 ± 0.05 µm) when compared to the pressed samples, with mean apparent density of 5.37 ± 0.08 g/cm3, apparent porosity of 1.56 ± 0.10% and grain size of 0.64 ± 0.02 µm. The performances of the samples were attested by the photocatalytic degradation of Rhodamine B (RhB) under UV-C irradiation (maximum intensity at 254 nm). The samples obtained by slip casting showed photocatalytic degradation between 80% and 90%, while the pressed samples showed degradation between 40% and 60%. The reuse of the photocatalysts was evaluated over five cycles of photocatalytic degradation, in which there was no loss of performance of the samples obtained by slip casting; however, the pressed samples showed a loss of photocatalytic efficiency starting from the third-cycle. Photocatalytic assays were carried out with different dye concentrations, in which the slip casting samples showed better photocatalytic efficiency (degradation of 80% for a RhB concentration of 10 mg/L) due to higher porosity and surface area compared to pressed samples, and there was a loss of performance in higher concentrations.

Synthesis of (Ca,Nd)TiO3 powders by complex polymerization, Rietveld refinement and optical properties.

Neodymium calcium titanate, (Ca(0.99)Nd(0.01))TiO(3) powders were synthesized by the complex polymerization method and heat treated at different temperatures for 2 h under air atmosphere. The structural evolution of these powders as a function of heat treatment temperature was analyzed by X-ray diffraction (XRD) and micro-Raman (MR) spectroscopy. The optical properties were investigated by Ultraviolet-visible (UV-vis) absorption spectroscopy and Photoluminescence (PL) measurements. XRD patterns, Rietveld refinement and MR spectra indicated that the powders heated treated at 750 degrees C for 2 h present an orthorhombic structure without secondary phases. UV-vis measurements suggested the presence of intermediary energy in disordered (Ca(0.99)Nd(0.01))TiO(3) powders. Broad and narrow bands were observed in the PL spectra of these powders when excited with 350 nm wavelength. The broad bands were associated to the structural defects and/or p-d electronic transitions while, the narrow bands were ascribed to f-f transitions arising from Nd(3+) ions.