Rectangular ZnO porous nano-plate assembly with excellent acetone sensing performance and catalytic activity

The controlled synthesis of a hierarchically assembled porous rectangular ZnO plate (2.5-3.5 mm length, 1.5-2.5 mm width and 100-150 nm thickness) from bulk ZnO without using any organic substrates, such as solvents/surfactants/structure-directing agents, is presented. The synthesized ZnO plates are single crystalline with exposed (10 (1) over bar0) facets on the flat surface, porous and formed through the calcination of a hydrozincite Zn-5(CO3)(2)(OH)(6)] intermediate. A gas sensor based on the synthesized porous ZnO architecture exhibited high sensitivity towards acetone even in low concentration (S = 3.4 in 1 ppm acetone) with good selectivity. The ZnO nanostructured material as a heterogeneous catalyst also showed excellent catalytic activity for the synthesis of 5-substituted-1H-tetrazoles (yield = 94%). Both the activities are superior than those of other reported ZnO based acetone sensors and heterogeneous catalysts. We believe that the improved properties of the synthesized ZnO nanostructure is due to the exposed (10 (1) over bar0) facets, and its porous and assembled structure, which provides a reasonably large accessible surface area, and facilitates diffusion and mass transport of gas or substrate molecules

Morphology-mediated tailoring of the performance of porous nanostructured Mn2O3 as an anode material

Tailoring of functional properties by varying the size and shape of porous nanostructured materials is an important frontier area of research. Herein, we report the successful synthesis of nanostructured Mn2O3 with desired 3D architectures such as porous hollow spheres, lotus shapes and tubular shapes, as well as aggregated nanoparticles, through the calcination of corresponding MnCO3 with the same architecture. Porous structures were formed upon evolution of CO2 during decomposition of the carbonate intermediate, and hollow structures were formed through a nonequilibrium interdiffusion process, i.e., the Kirkendall effect. The bare MnCO3 structures were synthesized using the chelating agents citric acid (CA), tartaric acid (TA), oxalic acid (OA), and ethylenediaminetetraacetic acid (EDTA), which mediated the growth of these MnCO3 structures by hydrothermal treatment of a precursor solution containing MnCl2, ammonium carbonate and chelating agent. A systematic evaluation of the effect of the morphology of the synthesized Mn2O3 on its performance as an anode material in Li-ion batteries reveals that the shape and the nature of pores of Mn2O3 strongly influence its Li-ion storage capacity. A superior specific capacity of 478 mAh g(-1) is obtained for hollow spheres with 38% retention after 30 cycles compared to other shapes due its high accessible surface area and inner hollow architecture

3D Hierarchically Assembled Porous Wrinkled-Paper-like Structure of ZnCo2O4 and Co-ZnO@C as Anode Materials for Lithium-Ion Batteries

Three dimensional (3D) hierarchically assembled porous transition metal oxide nanostructures are promising materials for next generation rechargeable Li-ion batteries (LIBs). Here, the controlled synthesis of 3D hierarchically porous ZnCo2O4 ``wrinkled-paper-like'' structure constructed from two-dimensional (2D) nanosheets (similar to 20 nm thick) through calcination of corresponding mixed metal carbonate intermediate is presented. The mixed metal hydroxy-carbonate intermediate with wrinkled-paper-like structure has been synthesized by a novel organic surfactant and organic solvent free protocol at reflux condition using an aqueous solution of corresponding metal salt and ammonium carbonate. Active-inactive nanocomposites of Co-ZnO@C with similar wrinkled-paper-like morphology with varying carbon content, have also been synthesized through carbonation of hydroxyl-carbonate intermediate followed by calcination (under reducing environment). Calcination of the carbon coated mixed metal carbonate results in phase separated uniform Co metal and ZnO particles embedded on carbon matrix. The results demonstrate that incorporation of similar to 23% carbon in the matrix significantly improves the performance as anode material in LIB by exhibiting high specific capacity and enhanced cycling performance. At a current density of 100 mAg(-1), it shows an excellent initial specific capacity of 527 mAhg(-1), which is maintained up to 50 cycles. In fact, a slight gradual increase in capacity with cycling has been observed

Hierarchically order porous lotus shaped nano-structured MnO2 through MnCO3: chelate mediated growth and shape dependent improved catalytic activity

Design of hierarchical nanostructures towards a specific morphology is an important research area due to their shape dependent properties. Here, 3D hierarchically assembled lotus shaped porous MnO2 is synthesized using a simple aqueous solution based chelating agent (citric acid) mediated growth of MnCO3 followed by calcination at 350 degrees C. MnCO3 in other shapes, such as rods, spheres and nano-aggregates, is also synthesized just by varying the chelating agents. It is observed that the geometry and strength of the chelating ligands has a crucial role in the controlled shape selective synthesis and based on this a probable chelating agent driven formation mechanism is discussed. The synthesized porous MnO2 shapes exhibit excellent shape dependent catalytic oxidation of alpha-pinene to verbenone using molecular oxygen as the oxidant. The lotus shaped porous MnO2 shows superior activity, with 94% conversion of alpha-pinene and 87% selectivity of verbenone, to that of other MnO2 shapes. The activity is reasonably high compared to heterogeneous as well as homogeneous catalysts reported in the literature and bulk MnO2 with respect to both their conversion and selectivity. The synthesized lotus shaped MnO2 also showed good catalytic activity towards oxidation of allylic compounds to corresponding ene-ones using molecular oxygen as oxidant and is reusable

3D Hierarchically Assembled Porous Wrinkled-Paper-like Structure of ZnCo₂O₄ and Co-ZnO@C as Anode Materials for Lithium-Ion Batteries

Three dimensional (3D) hierarchically assembled porous transition metal oxide nanostructures are promising materials for next generation rechargeable Li-ion batteries (LIBs). Here, the controlled synthesis of 3D hierarchically porous ZnCo₂O₄ “wrinkled-paper-like” structure constructed from two-dimensional (2D) nanosheets (∼20 nm thick) through calcination of corresponding mixed metal carbonate intermediate is presented. The mixed metal hydroxy-carbonate intermediate with wrinkled-paper-like structure has been synthesized by a novel organic surfactant and organic solvent free protocol at reflux condition using an aqueous solution of corresponding metal salt and ammonium carbonate. Active-inactive nanocomposites of Co-ZnO@C with similar wrinkled-paper-like morphology with varying carbon content, have also been synthesized through carbonation of hydroxyl-carbonate intermediate followed by calcination (under reducing environment). Calcination of the carbon coated mixed metal carbonate results in phase separated uniform Co metal and ZnO particles embedded on carbon matrix. The results demonstrate that incorporation of ∼23% carbon in the matrix significantly improves the performance as anode material in LIB by exhibiting high specific capacity and enhanced cycling performance. At a current density of 100 mAg^–1, it shows an excellent initial specific capacity of 527 mAhg^–1, which is maintained up to 50 cycles. In fact, a slight gradual increase in capacity with cycling has been observed

Abstracts of National Conference on Research and Developments in Material Processing, Modelling and Characterization 2020

This book presents the abstracts of the papers presented to the Online National Conference on Research and Developments in Material Processing, Modelling and Characterization 2020 (RDMPMC-2020) held on 26th and 27th August 2020 organized by the Department of Metallurgical and Materials Science in Association with the Department of Production and Industrial Engineering, National Institute of Technology Jamshedpur, Jharkhand, India. Conference Title: National Conference on Research and Developments in Material Processing, Modelling and Characterization 2020Conference Acronym: RDMPMC-2020Conference Date: 26–27 August 2020Conference Location: Online (Virtual Mode)Conference Organizer: Department of Metallurgical and Materials Engineering, National Institute of Technology JamshedpurCo-organizer: Department of Production and Industrial Engineering, National Institute of Technology Jamshedpur, Jharkhand, IndiaConference Sponsor: TEQIP-