Photocatalytic properties of solution combustion synthesized ZnO powders using mixture of CTAB and glycine and citric acid fuels

Photocatalytic properties of BiFeO3 powders synthesized by the mixture of CTAB and Glycine

Highly pure BiFeO₃ (BFO) powders were prepared by the solution combustion synthesis method using cetyltrimethylammonium bromide (CTAB) and glycine as fuels at various fuel-to-oxidant (φ) ratios. Microstructural characteristics, morphology, optical properties, and thermal analysis were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), diffuse reflectance spectroscopy (DRS), and differential thermal/thermogravimetry (DTA/TGA), respectively. The combusted powders prepared at different fuel content contained a small amount of impurity phases such as Bi₂₄Fe₂O₃₉ and Bi₂Fe₄O₉. During the calcination of BFO powders at 600 °C for 1 h, a nearly pure BFO phase was produced. Combusted powders photodegraded about 80% of methylene blue dye at φ = 2 through 90 min of visible light irradiation.

ZnO nanoparticles as efficient sunlight driven photocatalyst prepared by solution combustion method involved lime juice as biofuel

We have prepared high purity Zinc oxide (ZnO) nanoparticles (NPs) by solution combustion synthesis (SCS) method with the aid of lime juice extract. From powder X-ray diffraction (XRD) spectra, it is observed that the ZnO NPs possess single phase, hexagonal wurzite structure with sharp intense peak at (101) plane, agrees with the planes of SAED pattern. Further, the crystallite size is found to be around 18 nm. UV-Vis analysis shows strong UV absorbance band at 381 nm and PL measurements reveals the presence of strong UV emission at 347 nm along with few weak visible emissions. Optical studies infer the existence of lower recombination rate of electron-hole pair, influence the photocatalytic activity of ZnO. From XPS measurements, presence of oxygen rich states on surface are also confirmed (O 1 s states). The degradation performance and reusability of four different dyes (methylene blue (MB), methyl orange (MO), rhodamine B (RhB), Pararosaniline (PRA)) under UV and sunlight irradiations are carried out to illustrate the photo-catalytic activity in presence of a catalyst like ZnO NPs. Comparatively, about 98.8% of PRA and MB dyes are photodegraded at 90 and 75 min of sunlight irradiation, respectively. Among these two, PRA dye shows maximum degradation performance with shorter irradiation time along with good stability, which can be extend very well to minimize the pollution issues happening in society especially, industrial wastes.

Catalytic activity of porous manganese oxides for benzene oxidation improved via citric acid solution combustion synthesis

Various manganese oxides (MnO_x) prepared via citric acid solution combustion synthesis were applied for catalytic oxidation of benzene. The results showed the ratios of citric acid/manganese nitrate in synthesizing process positively affected the physicochemical properties of MnO_x, e.g., BET (Brunauer-Emmett-Teller) surface area, porous structure, reducibility and so on, which were in close relationship with their catalytic performance. Of all the catalysts, the sample prepared at a citric acid/manganese nitrate ratio of 2:1 (C2M1) displayed the best catalytic activity with T₉₀ (the temperature when 90% of benzene was catalytically oxidized) of 212℃. Further investigation showed that C2M1 was Mn₂O₃ with abundant nano-pores, the largest surface area and the proper ratio of surface Mn⁴⁺/Mn³⁺, resulting in preferable low-temperature reducibility and abundant surface active adsorbed oxygen species. The analysis results of the in-situ Fourier transform infrared spectroscopy (in-situ FTIR) revealed that the benzene was successively oxidized to phenolate, o-benzoquinone, small molecules (such as maleates, acetates, and vinyl), and finally transformed to CO₂ and H₂O.