Colloidal Sol–Gel Synthesis and Photocatalytic Activity of Nanoparticulate Nb₂O₅ Sols

Abstract

A detailed study of a novel synthesis via colloidal sol-gel route for obtaining nanoparticulate Nb 2 O 5 was performed. Parameters such as temperature and H + :Nb 5+ and Nb 5+ :H 2 O molar ratios were controlled in order to determine the best conditions of synthesis. Moreover, particle size distribution, zeta potential, structure by X-ray diffraction, and the photocatalytic activity of the particulate sols were also evaluated. The obtained results indicate that the colloidal sol-gel synthesis is a good alternative for obtaining Nb 2 O 5 either as stable nanoparticulate sol or as a nanosized powder. Nb 2 O 5 amorphous nanoparticles with an average size of 20 nm were obtained by controlling the synthesis variables. The heat-treatment process allowed the formation of Nb 2 O 5 with orthorhombic structure that transforms at higher temperatures to monoclinic phase. The highest photocatalytic activity was observed under k = 365 nm, the smallest UV energy used in the experimental tests.

One‐Step Synthesis of Nb2O5/C/Nb2C (MXene) Composites and Their Use as Photocatalysts for Hydrogen Evolution

“…As shown in Figure A, three characteristic diffraction peaks are observed in the XRD patterns of Nb 2 CT x , which is consistent with the literature . Characteristic diffraction peaks centered at 2 θ =16.9, 22.6, 28.5, 29.2, 36.5, 46.1, 50.9, and 55.2° are observed for the Nb 2 O 5 sample, and they are due to the (1 3 0), (0 0 1), (1 8 0), (2 0 0), (1 8 1), (0 0 2), (3 8 0), and (2 0 2) planes of the orthorhombic Nb 2 O 5 crystal (JCPDS 30‐0873), respectively. Apart from that, some peaks corresponding to the monoclinic Nb 2 O 5 phase (JCPDS 19‐0859) are also observed, and this is indicative of the presence of a mixture of phases in the Nb 2 O 5 sample.…”

“…Characteristic diffraction peaks centered at 2 θ =16.9, 22.6, 28.5, 29.2, 36.5, 46.1, 50.9, and 55.2° are observed for the Nb 2 O 5 sample, and they are due to the (1 3 0), (0 0 1), (1 8 0), (2 0 0), (1 8 1), (0 0 2), (3 8 0), and (2 0 2) planes of the orthorhombic Nb 2 O 5 crystal (JCPDS 30‐0873), respectively. Apart from that, some peaks corresponding to the monoclinic Nb 2 O 5 phase (JCPDS 19‐0859) are also observed, and this is indicative of the presence of a mixture of phases in the Nb 2 O 5 sample. The diffraction peaks of orthorhombic and monoclinic Nb 2 O 5 can be observed for the oxidized Nb 2 CT x samples, but no diffraction peak of Nb 2 CT x is observed, which is consistent with previous reports for the oxidation of MXenes .…”

Fast microwave‐assisted hydrothermal synthesis of TiNb2O7 nanoparticles

“…According to the surface area data presented in Table , it is possible to infer that the thermal treatment led to a decrease in the surface area of the samples (as expected). However, it is worth highlighting that the combined microwave sol‐gel synthesis method is suitable for the preparation of nanomaterials with high surface area, showing superior results when compared to the colloidal sol‐gel method alone …”

“…NbCl 5 was added to acetic acid glacial (HAc, C 2 H 4 O 2 , 99%, Sigma‐Aldrich, Germany) according to the procedure previously reported by Falk et al . Subsequently, the obtained solution and the TIPO were hydrolyzed adding them to a mixture of distilled water and nitric acid (HNO 3 65%, Vetec) in a H 2 O:(Nb 5+ ,Ti 4+ ) = 200:1 and H + :(Nb 5+ ,Ti 4+ )= 0.1 molar ratios.…”

“…Among the synthesis methods, the sol‐gel process is one of the most used for producing nanomaterials, thin films, dense ceramics, and even complex nanostructures such as aerogels . This method enables controlling stoichiometry, porosity, and particle size, which are factors that influence properties and applications .…”