Effect of Nb/C ratio in the morphological, structural, optical and photocatalytic properties of novel and inexpensive Nb2O5/carbon xerogel composites

Abstract This work explores the development of hybrid Nb2O5/carbon xerogel photocatalysts. The precursor materials used, such as tannin and recycled niobium scraps, enhance the economic and environmental aspects of the synthesis. The materials were characterized by diffuse reflectance spectroscopy, scanning electron microscopy, dispersive energy spectroscopy, infrared spectroscopy, Raman spectroscopy and X-ray diffraction. The photocatalytic action of the material was evaluated by methylene blue decomposition as determined by UV–visible spectroscopy. Anhydrous niobium oxide has a hexagonal structure. The X-ray profiles of the materials developed (XC-wNb) are similar to Nb2O5, confirming the presence of inorganic oxide in the matrix of these composites. The chemical elements that compose the samples are homogeneously distributed on the surface of the samples, confirming the dispersion of the oxide in the carbonaceous matrix. The XC-wNb absorbs radiation in a considerably wider range than inorganic oxides, in this case, for the entire wavelength range used in the experiments, thereby suggesting the synergistic effect of xerogel and niobium oxide on the optical properties of the XC-wNb samples. All XC-wNb presented photocatalytic activity under visible radiation, evidencing the beneficial coupling effect on the photocatalytic properties of the material. The XC-24Nb was the most effective photocatalyst at the wavelength used due its composition, morphological and photochemical properties. The methylene blue photodegradation is controlled to a greater extent by reaction with the OH • radical. The XC-24Nb also presents high stability and reusability, which are optimal properties for industrial application.