Three-dimensional potassium niobate nanoarray on vermiculite for high-performance photocatalyst fabricated by an in situ hydrothermal process

Abstract

Three-dimensional (3D) potassium niobate nanoarray/vermiculite (KNbO 3 /VMT) was synthesized by an in situ hydrothermal method using niobium chloride as the niobium resource. Scanning electron microscopy, high resolution transmission electron microscopy, X-ray diffraction, Fourier transform infrared and X-ray photoelectron spectroscopy tests were used to confirm that KNbO 3 nanoneedles have been grown both on the outer and inner surfaces of natural layered VMT and the growth mechanism of the well-aligned KNbO 3 nanoarray grown on mineral VMT was attributed to the existence of Nb species. The photocatalytic performance of the as-prepared composite was investigated using the photodegradation of methylene blue (MB) under illumination. MB was removed from aqueous solution by fully taking advantage of the good absorption property of VMT and photocatalytic property of KNbO 3 , and visible light was used in the process. After illumination for 105 min, the removal rate of MB in aqueous solution could be higher than 81%. The removal of MB via adsorption-degradation synergy of the structured composite was much better than that of pristine VMT and KNbO 3 powder with the same amount of addition, respectively. Moreover, the environmentally friendly KNbO 3 /VMT material is easy to synthesize and is expected to be a promising structured photocatalyst for the removal of dyes.

Facile Fabrication of N‐Doped K2Nb2O6 Nanocrystals with Defective Pyrochlore Structure for Improved Visible‐Light Photocatalytic Hydrogen Production

“…Figure a shows the Nb 3 d spectrum of 6N–K 2 Nb 2 O 6 , which could be fitted into four peaks. The two prominent peaks centered at 206.27 and 208.97 eV could be assigned to Nb 5+ , whereas the peak centered at 206.59 and 209.46 eV corresponds to Nb 4+ , [ 41,42 ] confirming the formation of Nb 4+ species in 6N–K 2 Nb 2 O 6 . The N 1 s spectrum of the 6N–K 2 Nb 2 O 6 sample is shown in Figure 3b, which contains three binding energy peaks at 393.4, 395.4, and 401.9 eV.…”

Laser‐induced Fano interference subsumed by electron–phonon coupling in orthorhombic KNbO3nano‐bricks: An ab initio vibrational and Raman spectroscopic investigation

“…The peak at 659 cm −1 is assigned to the stretching vibrations in the corner‐sharing NbO 6 , whereas the peaks at 501 and 817 cm −1 are related to the bonds within the edge‐shared NbO 6 octahedra. Among the couple of Wyckoff orientations, the edge‐shared octahedra are known to exhibit larger structural distortions in reference to the corner‐shared NbO 6 octahedra that strongly apply fluctuations in the bond‐length 33–36 . The peaks at 1707, 2293, and 2390 cm −1 are indicative of axial deformation and asymmetric stretching vibrations of the adsorbed CO 2 molecules.…”

“…Among the couple of Wyckoff orientations, the edge-shared octahedra are known to exhibit larger structural distortions in reference to the cornershared NbO 6 octahedra that strongly apply fluctuations in the Nb -O bond-length. [33][34][35][36] The peaks at 1707, 2293, and 2390 cm À1 are indicative of axial deformation and O ¼ C ¼ O asymmetric stretching vibrations of the adsorbed CO 2 molecules. Along with CO 2 gas, some amount of moisture is likely chemisorbed in the surface of the nanoparticles.…”

Perovskite Oxides Prepared by Hydrothermal and Solvothermal Synthesis: A Review of Crystallisation, Chemistry, and Compositions

“…[127] Hydrogen evolution from aqueous formic acid [143] KNbO3 has been similarly explored for its photocatalytic activity. [131][132]136] Wang et al used vermiculite as a substrate on which to grow KNbO3 needles that showed photoactivity for degradation of methyl blue, [134] while nitrogen-doping of KNbO3 prepared hydrothermally was possible by heat treatment in the presence of urea to tune photocatalytic properties. [144] Using ethanol as solvent and NbCl5 as precursor, Nb 4+containing KNbO3 was prepared with improved water splitting properties; these could also be readily nitrided in a second step with ammonia to give a surface modified with Nb4N5 that showed enhanced photocatalysis properties, ascribed to the introduction of some Nb 4+ , and the junction between the oxide and nitride.…”