Tricobalt tetraoxide (CoO), a spinel-structured nanoparticle which possesses mixed oxidation states, has been synthesized via a Punica granatum (P. granatum, pomegranate) seed extract-mediated green reaction and has been investigated for its superior catalytic activity in three applications, which include (i) photodegradation of textile dye effluents (TDE) collected from the dyeing industry, Tiruppur, Tamil Nadu, India, (ii) catalytic hydrogenation of nitro-aromatic pollutants such as 4-nitrophenol and 4-nitroaniline, and (iii) antibacterial potential in biomedical applications. Prior to the application studies, the synthesized CoO spinel nanoparticles (CoO-NPs) were characterized by well-known established techniques such as X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), energy dispersive X-ray analysis (EDX), diffuse reflectance spectroscopy (DRS), photoluminescence spectroscopy (PL), and Raman and FT-IR spectroscopies. We have also discussed the probable mechanism and kinetic studies of the catalytic activity of the CoO-NPs. Finally, we concluded that the design and development of novel, economic and green synthesis-mediated catalysts such as CoO-NPs can exhibit efficient catalytic activity in diverse fields, which is necessary for environmental remediation.

Green synthesis of Co3O4-NPs by a HPCM method using Azadirachta indica leaf extract is reported. HRTEM shows hollow sphere like NPs with polycrystalline nature and it is used in catalytic applications.

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Supercapacitors are perfect energy storage devices; they can be charged almost instantly and release energy over a long period. Another advantage of using supercapacitors is their multipletimes chargeable behavior with minimum degradation in performance. Herein, we report the nanoporous activated carbon based modified electrodes prepared by using phosphoric acid (PA) activation method at different temperatures (600, 700, 800, and 900 °C) using bio-waste precursor, Tamarindus indica (T. indica) fruit shell. Because of their excellent energy storage capacity, in the present work, supercapacitive behavior of the nanoporous activated carbon based modified electrode has been demonstrated and hence the electrochemical properties of the developed supercapacitor electrodes are analyzed using cyclic voltammetry, galvanostatic charge–discharge measurements, electrochemical impedance spectroscopy and cycling studies using 1 M KOH as the electrolyte. The developed supercapacitor nanoporous activated carbon materials are characterized by X-ray diffraction, functional group analysis, surface area and morphological studies.

Hierarchical ordered ZSM-5 zeolites were successfully synthesized by a template-free hydrothermal treatment using rice joints ash as the source of silica. The formation of hierarchical ordered ZSM-5 zeolites and its physicochemical properties were investigated systematically. The mineralogical phases, morphology, surface area and porosity, acidity and thermal stability of the synthesized hierarchical materials were investigated using XRD, FT-IR, HR-SEM, N2 adsorption-desorption (BET) analysis, NH3-TPD and TGA/DTA analysis. The excellent catalytic activity of hierarchical ordered ZSM-5 zeolites (150 °C) was revealed in the selective oxidation of toluene to the corresponding benzaldehyde with 82% conversion and 94% selectivity. The material was evaluated for the oxidation of toluene in the presence of H2O2 as the oxidizing agent and 1,4-dioxane solvent. The obtained results noted that the material was highly active, stable and can be recycled at least four times without a loss of catalytic efficiency. The crystallization was carried out in an autoclave for 5 days maintained at a temperature of 150 °C for the transformation of RJA into hierarchical ZSM-5 zeolite structure as well as to achieve high crystallinity.