DFT and experimental investigations on the photocatalytic activities of NiO nanobelts for removal of organic pollutants

NiO nanobelts synthesized using the hydrothermal method are explored for photocatalytic degradation of organic pollutants like RhB, MO, MB, and CV. The XPS analysis confirmed the formation of the stoichiometric NiO nanobelts. Few micrometer long cubic crystalline NiO nanobelts of the average thickness of ∼75 nm delivered a bandgap of 4.07 eV. The FTIR studies revealed that the mesoporous NiO nanobelts delivered stable photocatalytic activities after controlled irradiation under a xenon lamp. The kinetic studies showed the 79.1, 82.7, 76.7, and 89% degradation of MO, MB, CV, and RhB after 140 min at the rate constants (k) of 0.007, 0.008, 0.009, and 0.012 min−1, respectively. Complementary first-principles Density Functional Theory (DFT) and scavenging studies revealed the chemical picture and influence of the , and photogenerated from NiO nanobelts in the photocatalytic degradation of organic dyes. These studies corroborate the use of the NiO nanobelts in the stable and eco-friendly photocatalytic degradation activities of a wide range of organic pollutants

Photocatalytic behavior of Ba(Sb/Ta)2O6 perovskite for reduction of organic pollutants: Experimental and DFT correlation

We have synthesized closely packed hexagonal 2D plates and clustered nanoparticle morphologies of Ba(Sb/Ta)2O6 (BSTO) perovskite via the polymerizable complex method for photocatalytic dye degradation activities. The BSTO crystallized in a hexagonal structure. The presence of Ba2+, Sb5+, Ta5+, and O2− chemical states identified from XPS confirmed the formation of mixed Ba(Sb/Ta)2O6 phase accompanied with a minor amount of TaOx. Furthermore, BSTO showed excellent photocatalytic activity for the degradation of various organic dyes. The kinetic studies revealed 65.9%, 77.3%, 89.8%, and 84.2%, of Crystal Violet (CV), Methylene Blue (MB), Rhodamine blue (RhB), and Methylene Orange (MO), respectively, after irradiation of 180 min without using a cocatalyst. The formation of and OH−surface radicals, which are believed to facilitate the degradation of the dyes, are unveiled through first-principles Density Functional Theory (DFT) calculations and scavenging studies. Our results suggest that BSTO holds promise as an excellent photocatalyst with better degradation efficiency for various organic dyes

Solution-processed Cd-substituted CZTS nanocrystals for sensitized liquid junction solar cells

The Earth-abundant kesterite Cu2ZnSnS4 (CZTS) exhibits outstanding structural, optical, and electronic properties for a wide range of optoelectronic applications. However, the efficiency of CZTS thin-film solar cells is limited due to range of factors, including electronic disorder, secondary phases, and the presence of anti-site defects, which is key factor limiting the Voc. The complete substitution of Zn lattice sites in CZTS nanocrystals (NCs) with Cd atoms offers a promising approach to overcome several of these intrinsic limitations. Herein, we investigate the effects of substitution of Cd2+ into Zn2+ lattice sites in CZTS NCs through a facile solution-based method. The structural, morphological, optoelectronic, and power conversion efficiencies (PCEs) of the NCs synthesized have been systematically characterized using various experimental techniques, and the results are corroborated by first-principles density functional theory (DFT) calculations. The successful substitution of Zn by Cd is demonstrated to induce a structural transformation from the kesterite phase to the stannite phase, which results in the bandgap reducing from 1.51 eV (kesterite) to 1.1 eV (stannite), which is closer to the optimum bandgap value for outdoor photovoltaic applications. Furthermore, the PCE of the novel Cd-substituted liquid junction solar cell underwent a four-fold increase, reaching 1.1%. These results highlight the importance of substitutional doping strategies in optimizing existing CZTS-based materials to achieve improved device characteristics

X-ray Diffraction Study of a Large-Scale and High-Density Array of One-Dimensional Crystalline Tantalum Pentoxide Nanorods

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Highly stable supercapacitive performance of one-dimensional (1D) brookite TiO₂ nanoneedles

We report the highly stable supercapacitive performance of one-dimensional (1D) nanoneedles of brookite (β) TiO2 synthesized on a conducting glass substrate. The 1D β-TiO2 nanoneedles synthesized over a large area array utilizing hot-filament metal vapor deposition (HFMVD) were ∼24–26 nm wide, ∼650 nm long and tapered in a downward direction. X-ray photoemission spectroscopy (XPS) revealed their chemical properties and stoichiometric Ti and O composition. The 1D β-TiO2 nanoneedles execute as parallel units for charge storage, yielding a specific capacitance of 34.1 mF g−1. Electrochemical impedance spectroscopy revealed that the large surface area and brookite crystalline nature of the 1D nanoneedles provided easy access to Na+ ions, and resulted in low diffusion resistance, playing a key role in their stable charging–discharging electrochemical mechanism. Moreover, the non-faradic mechanism of these nanoneedles delivered better durability and high stability up to 10 000 cycles, and a columbic efficiency of 98%. Therefore, 1D β-TiO2 nanoneedles hold potential as an electrode material for highly stable supercapacitive performance with long cycle lifetime.publishe

Photocatalytic activity of MnTiO3 perovskite nanodiscs for the removal of organic pollutants

MTO nanodiscs synthesized using the hydrothermal approach were explored for the photocatalytic removal of methylene blue (MB), rhodamine B (RhB), congo red (CR), and methyl orange (MO). The disc-like structures of ~16 nm thick and ~291 nm average diameter of stoichiometric MTO were rhombohedral in nature. The MTO nanodiscs delivered stable and recyclable photocatalytic activity under Xe lamp irradiation. The kinetic studies showed the 89.7, 80.4, 79.4, and 79.4 % degradation of MB, RhB, MO, and CR at the rate constants of 0.011(±0.001), 0.006(±0.001), 0.007(±0.0007), and 0.009 (±0.0001) min−1, respectively, after the 180 min of irradiation. The substantial function of photogenerated holes and hydroxide radicals pertaining to the dye removal phenomena is confirmed by radical scavenger trapping studies. Overall, the present studies provide a way to develop pristine and heterostructure perovskite for photocatalysts degradation of various organic wastes

Bifunctional Co0.75Fe0.25@C nanocomposite towards zero waste approach: Organic pollutants removal and OER electrocatalysis

Here, we report synthesis of magnetic nanocomposite with zero-waste approach for organic pollutant removal and oxygen evolution reaction. The nanocomposite was synthesized using agriculture waste soaked with Co2+-Fe3+ metal ions at 900 °C and characterized using FESEM, HRTEM, PXRD, Zeta-potential, and VSM techniques. The nanocomposite shows an impressive adsorbent property for organic dyes (90-96 % removal), and pharmaceutical drug (paracetamol, 84% removal), along with individually used ‘hair dye’ (95% removal) in 5 min only. The recyclability of the nanocomposite demonstrates the practical benefits of the material for waste water remediation. Interestingly, after the adsorption, the generated secondary waste (exhausted dye adsorbed nanocomposite) is used as oxygen evolution reaction (OER) electrocatalyst. The dye-adsorbed nanocomposite shows good OER activity with an overpotential of 264 mV at 10 mA/cm2 with good stability upto 10 h. This study sheds light on the reuse and recycling of the secondary waste of the adsorption process to develop efficient OER electrocatalysts and shows a zero-waste approach towards the environment