Self-Assembled Interwoven Nanohierarchitectures of NaNbO₃ and NaNb_1–xTa_xO₃ (0.05 ≤ x ≤ 0.20): Synthesis, Structural Characterization, Photocatalytic Applications, and Dielectric Properties

Abstract

Dependence on fossil fuels for energy purposes leads to the global energy crises due to the nonrenewable nature and high CO 2 production for environmental pollution. Therefore, new ways of nanocatalysis for environmental remediation and sustainable energy resources are being explored. Herein, we report a facile surfactant free, low temperature, and environmentally benign hydrothermal route for development of pure and (5, 10, 15, and 20 mol %) Ta-doped horizontally and vertically interwoven NaNbO 3 nanohierarchitecture photocatalysts. To the best of our knowledge, such a type of hierarchical structure of NaNbO 3 has never been reported before, and changes in the microstructure of these nanoarchitectures on Ta-doping has also been examined for the first time. As-synthesized nanostructures were characterized by different techniques including X-ray diffraction analysis, electron microscopic studies, X-ray photoelectron spectroscopic studies, etc. Ta-doping considerably affects the microstructure of the nanohierarchitectures of NaNbO 3 , which was analyzed by FESEM analysis. The UV–visible diffused reflectance spectroscopy study shows considerable change in the band gap of as-synthesized nanostructures and was found to be ranging from 2.8 to 3.5 eV in pure and different mole % Ta-doped NaNbO 3 . With an increase in dopant concentration, the surface area increases and was equal to 5.8, 6.8, 7.0, 9.2, and 9.7 m 2 /g for pure and 5, 10, 15, and 20 mol % Ta-doped NaNbO 3 , respectively. Photocatalytic activity toward the degradation of methylene blue dye and H 2 evolution reaction shows the highest activity (89% dye removal and 21.4 mmol g –1 catalyst H 2 evolution) for the 10 mol % NaNbO 3 nanostructure which was attributed to a change in the conduction band maximum of the material. At 100 °C and 500 kHz, the dielectric constants of pure and 5, 10, 15, and 20 mol % Ta-doped NaNbO 3 were found to be 111, 510, 491, 488, and 187, respectively. The current study provides the rational insight into the design of nanohierarchitectures and how microstructure affects different properties of the material upon doping.

Review on Metals and Metal Oxides in Sustainable Energy Production: Progress and Perspectives

“…Other semiconductor photocatalysts were explored to replace TiO 2 with higher catalytic activity. Farooq et al have recently developed NaNbO 3 as a semiconductor photocatalyst for H 2 evolution application and investigated the effect of doping on photocatalytic properties of NaNbO 3 . NaNbO 3 showed a band gap comparable to that of TiO 2 and was investigated for photocatalytic application in the UV region of the solar spectrum by different researchers.…”

Harvesting Green Hydrogen by Self‐Propelling Built‐in Electric Field Photo/Electro‐catalytic Performance of DyCrO3Nanoparticles Developed by Reverse Microemulsion Route

“…[7] Currently, perovskite oxides that can catalyze both OER and HER are scarce, especially in bulk form. [8,9] Nevertheless, we summarizes few significant OER/HER/ORR studies of various class of materials such as TbFeO 3 , [10] Cu-doped GdFeO 3 , [11] GdFeO 3 / C 3 N 4 , [12] Sr-doped BiFeO 3 , [13] NaNbO 3 /NaNb 1-x Ta x O 3 , [14] PtO x + NiO j GdFeO 3 [15] and Fe 3 O 4 À CoP x nanoflowers. [16] Another intriguing approach to address the energy and environmental issues is through semiconductor-based photocatalysts that use sunlight to generate hydrogen from water.…”

Oxide based Heterostructured Photocatalysts for CO2 Reduction and Hydrogen Generation

“…[27,28] TiO 2 assisted CO 2 photo-reduction and H 2 evolution via photocatalytic water splitting in the aqueous system motivated researchers to exploit different types of metal oxide photocatalysts such as SnO 2 , ZnO, WO 3 , Fe 2 O 3 , MoO 3 , CuWO 4 , ZnGa 2 O 4 , RuO 2 , NaNbO 3 and KNbO 3 for the efficient photocatalytic CO 2 reduction and H 2 evolution. [29][30][31][32][33][34][35] Among renewable energy sources, H 2 fuel has gained the wide interest of researchers owing to its efficiency. H 2 fuel has specific energy density thrice of fossil derivatives and it can be generated from diverse sources such as water, biogas and sewage sludge.…”

“…This leads to an accelerated frequency between metal oxide surface sites and CO 2 which plays the pivotal role in the electron transfer during the redox reactions and also induces the decreasing rate of recombination of photo‐generated charge carriers [27,28] . TiO 2 assisted CO 2 photo‐reduction and H 2 evolution via photocatalytic water splitting in the aqueous system motivated researchers to exploit different types of metal oxide photocatalysts such as SnO 2 , ZnO, WO 3 , Fe 2 O 3 , MoO 3 , CuWO 4 , ZnGa 2 O 4 , RuO 2 , NaNbO 3 and KNbO 3 for the efficient photocatalytic CO 2 reduction and H 2 evolution [29–35] . Among renewable energy sources, H 2 fuel has gained the wide interest of researchers owing to its efficiency.…”