Cobalt Oxides with Various 3D Nanostructured Morphologies for Catalytic Reduction of 4-Nitrophenol: A Comparative Study (original) (raw)
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Truncated Edge Cuprous Oxide Cube Architecture for Reduction of Nitrophenols
South African Journal of Chemistry, 2021
Truncated cubic Cu-oxide nanocrystals with edge lengths of ca. 600 nm were prepared employing the low-cost copper (II) chloride as the precursor. XRD revealed that the truncated cubic Cu-oxide nanocrystals are present in both the CuI and Cu0 state. XPS characterisation gives insight into the amount of each state present in the as-prepared, oxidised, reduced and recovered catalyst species. The catalytic activity of the truncated cubic Cu-oxide nanocrystals was tested for the reduction of nitrophenols using NaBH4. After one catalytic cycle of the reduction of 4-nitrophenol, the activity almost halved. The SEM images revealed that the recovered catalyst showed some disfigurement of the structure, and XPS confirmed the reduction of the CuI to metallic Cu0. Keywords: Cu-oxide, truncated cubic nanocrystal, nitrophenol, catalysis, X-ray photoelectron spectroscopy.
Mesoporous cobalt oxides were synthesized using an inverse surfactant micelle method. The prepared materials are mono-dispersed nanoparticle aggregates with connected, well defined intra-particle voids. Powder X-ray diffraction, N 2 sorption, scanning electron microscopy and transmission electron microscopy revealed that both pore and nanoparticle sizes are enlarged with thermal treatment temperatures. Nitrogen sorption experiments revealed that the pore diameters increased from 12.1 to 31.9 nm with the final heat treatment increase from 150 to 550 • C. The reduction of 4-nitrophenol has been chosen as a well-controlled model reaction allowing us to determine the catalytic activity as a function of crystallite size and pore diameter. A comparison of the various cobalt oxide catalysts is made in terms of Langmuir-Hinshelwood kinetics.
Morphology Controlled CuO Nanostructures for Efficient Catalytic Reduction of 4-Nitrophenol
Catalysis Letters, 2019
Catalytic transformation of nitroaromatic compounds in wastewater using nanostructured catalysts is a promising method for wastewater treatment. Here, we report a systematic study on morphology-dependent catalytic activity of CuO nanostructures for efficient reduction of 4-nitrophenol (4-NP) in water. The morphology of CuO nanostructures was controllably varied from nanorods, nanosheets and hierarchical 3D flower-like structures by simply varying ammonia concentration in a simple wet chemical approach. Catalytic transformation of toxic 4-NP into useful 4-aminophenol by the prepared nanostructured CuO samples were investigated. The impact of morphology on the catalytic activity of nanostructured CuO catalysts was examined. It was observed that hierarchical 3D flower-like CuO catalysts show enhanced catalytic activity as compared to nanorods and nanosheets. The origin of this morphology-dependent catalytic activity of CuO nanostructures is discussed.
Nanocatalytic Assemblies for Catalytic Reduction of Nitrophenols: A Critical Review
Critical Reviews in Analytical Chemistry, 2019
Nitrophenol is common carcinogenic pollutant known for its adverse effects on human beings and aquatic life. During the last few decades, the chemical reduction of nitrophenol compounds has been widely reported as the advanced removal methodology for such hazardous dyes from aqueous reservoirs. Many researchers have utilized different nanocatalytic systems using sodium borohydride (NaBH 4) as the reducing agent for acquiring industrially useful reduction product of aminophenol by carrying out the chemical reduction of nitrophenols. Polymeric material supported monometallic nanoparticles are widely reported catalyst for the degradation of 2-nitrophenol (2-NP) and 4-nitrophenol (4-NP). This review critically discusses the pros and cons of numerous supporting mediums of nanocatalytic assemblies used for the immobilization of nanomaterials. Mechanism and kinetic analysis of the reduction reaction of 2-NP and 4-NP have also been explained in this study. In addition, recent literature has also been effectively summarized in the tabular form for developing a better understanding of the reader. Pictorial representation of key nanocatalytic assemblies and catalytic reduction mechanism has also been narrated in this study.
Para-nitrophenol reduction on solvothermally prepared cobalt@silica core–shell catalysts
Reaction Kinetics, Mechanisms and Catalysis, 2017
Cobalt supported solids on silica have been prepared as core-shell nanocomposites and via a classical impregnation of commercial and prepared silica. The solids have been characterized by AAS, XRD, N 2 adsorption-desorption, UV-Vis spectroscopy and SEM-EDX techniques. The catalytic activity of the solids was probed in the p-nitrophenol reduction in presence of NaBH 4. The core-shell solid presented small particle size, high specific surface area, good cobalt dispersion and small gap energy value. All these characteristics contribute to improving the catalytic performance of this solid compared to the solids prepared via silica impregnation and containing the same amount of cobalt. Keywords 4-Nitrophenol reduction Á Cobalt catalysts Á Core-shell nanocomposites Á Solvothermal Á Self-assembly Á Wetness impregnation Electronic supplementary material The online version of this article (
A soft hydrogel reactor for cobalt nanoparticle preparation and use in the reduction of nitrophenols
Applied Catalysis B-environmental, 2010
Bulk poly(2-acrylamido-2-methyl-1-propansulfonic acid) (p(AMPS)) hydrogels were prepared by irradiation of an aqueous solution of AMPS in the presence of crosslinker and photoinitiator. These p(AMPS) hydrogel networks were utilized for in situ cobalt nanoparticle synthesis by reduction of metal ions absorbed into the hydrogel network with a reducing agent, i.e., NaBH4. TEM images confirmed that Co particles are about 100 nm in size. The hydrogel network with embedded Co nanoparticles was utilized as a catalyst in the reduction of 4-nitrophenol (4-NP) and 2-nitrophenol (2-NP) in aqueous media in the presence of an excess amount of NaBH4. The kinetics of the reduction reaction under different reaction conditions was investigated to determine the activation parameters. Activation energies are 27.8 kJ mol−1 and 39.3 kJ mol−1 for 4-NP and 2-NP, respectively. It was found that hydrogel–Co composites were 99% active after 5 days storage.▶ Elastic hydrogel reactor. ▶ In situ catalyst synthesis. ▶ Hydrogel-composite catalyst systems. ▶ Co nanoparticle embedded in environmentally sensitive flexible hydrogel network.
Reduction of 4-Nitrophenol as a Model Reaction for Nanocatalysis
Noble metal nanocomposites have received a great deal of attention in the field of catalysis due to their unique properties, which are directly related to their shapes and sizes. To investigate and derive a definite conclusion about the catalytic activity of various nanocatalysts with different sizes, shapes, and even porosities, a model reaction needed to be selected. The reduction of 4-nitro-phenol (4-NP) by NaBH 4 has been widely used as this model reaction, since it is easy to monitor with simple and fast analytical techniques, and there are no by-products. This reaction is also valuable in the view of green chemistry since 4-NP, one of the toxic substance in the wastewater, is converted into a commercially important substance, 4-aminophenol (4-AP). Here we present an overview of the mechanistic studies into 4-NP reduction, followed by a comprehensive overview of materials evaluated for this reaction.