Showing papers by "Andrews Nirmala Grace published in 2019"

Natural biomass derived hard carbon and activated carbons as electrochemical supercapacitor electrodes

Abstract: With every moving day, the aspect that is going to be the most important for modern science and technology is the means to supply sufficient energy for all the scientific applications. As the resource of fossil fuel is draining out fast, an alternative is always required to satisfy the needs of the future world. Limited resources also force to innovate something that can utilise the resource more efficiently. This work is based on a simple synthesis route of biomass derived hard carbon and to exploring the possibility of using it as electrochemical supercapacitors. A cheap, eco-friendly and easily synthesized carbon material is utilized as electrode for electrochemical energy-storage. Four different hard carbons were synthesized from KOH activated banana stem (KHC), phosphoric acid treated banana stem derived carbons (PHC), corn-cob derived hard carbon (CHC) and potato starch derived hard carbons (SHC) and tested as supercapacitor electrodes. KOH-activated hard carbon has provided 479.23 F/g specific capacitance as calculated from its cycle voltammograms. A detailed analysis is done to correlate the results obtained with the material property. Overall, this work provides an in depth analysis of the science behind the components of an electrochemical energy-storage system as well as why the different characterization techniques are required to assess the quality and reliability of the material for electrochemical supercapacitor applications.

Pt-free, low-cost and efficient counter electrode with carbon wrapped VO 2 (M) nanofiber for dye-sensitized solar cells

Abstract: The present study reports the use of one-dimensional carbon wrapped VO2(M) nanofiber (VO2(M)/C) as a cost-effective counter electrode for dye-sensitized solar cells (DSSCs); where M denotes monoclinic crystal system. Uniform short length nanofiber was synthesised by a sol-gel based simple and versatile electrospinning and post carbonization technique. The investigation of nanostructure and morphological analysis were performed by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), and transmission electron microscope (TEM) with EDAX. The electrochemical response was comprehensively characterized by cyclic voltammetry, electrochemical impedance spectroscopy and Tafel polarization. The electrochemical analysis of the VO2(M)/C nanofiber counter electrode exhibits significant electrocatalytic activity towards the reduction of triiodide and low charge transfer resistance at the electrode-electrolyte interface. The DSSCs fabricated with carbon-wrapped VO2(M) nanofiber CE showed high power conversion efficiency of 6.53% under standard test condition of simulated 1SUN illumination at AM1.5 G, which was comparable to the 7.39% observed for conventional thermally decomposed Pt CE based DSSC under same test conditions. This result encourages the next step of modification and use of low-cost VO2(M) as an alternate counter electrode for DSSCs to achieve a substantial efficiency for future energy demand.

Role of MIL-53(Fe)/hydrated–dehydrated MOF catalyst for electrochemical hydrogen evolution reaction (HER) in alkaline medium and photocatalysis

Abstract: The role of breathing behavior in hydrated and dehydrated forms of MIL-53(Fe) is investigated here. The material can be used as an efficient electrocatalyst and photocatalyst for a hydrogen evolution reaction (HER) in an alkaline medium and the same was further tested for the degradation of organic pollutants. The as-synthesized MIL-53(Fe)/hydrated and dehydrated forms were characterized by different analytical techniques to study their structure, morphology, surface analysis, thermal, physical and chemical properties. The breathing behavior of the hydrated and dehydrated forms of MIL-53(Fe) was studied through BET surface analysis. Our results show a low onset potential (−0.155 V and −0.175 V), Tafel slope (71.6 mV per decade, 88.7 mV per decade) and a large exchange current density (1.6 × 10−4 mA cm−2 and 2.5 × 10−4 mA cm−2). Hydrated and dehydrated MIL-53(Fe) degraded an RhB dye solution within 30 minutes thus proving their efficiency as efficient photocatalysts.

Iron Oxide Nanomaterials for Water Purification

Abstract: The spread of a wide range of contaminants in surface water and groundwater has become a critical issue worldwide due to population growth, industrialization, and long-term droughts. It is necessary to control the harmful effects of these contaminants and improve the human living environment. There is a need for the development of various technologies and adsorbents to remove toxic pollutants from water. Among the various nanoadsorbents, nanoscale magnetite particles (approximately one billion times smaller [by volume] than microscale particles) are being extensively researched for the treatment of water and wastewater. The present chapter deals with the utilization of iron oxide nanomaterials for water purification in light of their unique properties (such as extremely small size, high surface-area-to-volume ratio, surface modifiability and excellent magnetic properties). Nanomaterials such as iron oxide nanoparticles are efficient adsorbents because they combine magnetic separation with ionic exchange capacity for heavy metal removal. A number of environmental cleanup technologies have been proposed in wastewater treatment with the use of iron oxide nanomaterials as nanosorbents and photocatalysts. In addition, iron-oxide-based immobilization technology for enhancing removal efficiency of hazardous materials tends to be an innovative research point. This chapter outlines the recent developments in the application of iron oxide nanomaterials for water treatment. A detailed review is addressed to the utilization of iron oxide nanomaterials as nanoadsorbents as well as their utility as photocatalysts. The practical potential and likely environmental fate when iron oxide nanomaterials are discharged is also discussed.

Process optimisation for green synthesis of ZnO nanoparticles and evaluation of its antimacrofouling activity

Abstract: In recent years, considerable attention has been given to the plant-mediated synthesis of nanoparticles because it is an eco-friendly method compared to the synthesis by chemical route. This study aims to optimise the biosynthesis of zinc oxide nanoparticles (ZnO-NPs) mediated by coconut water using response surface methodology (RSM). The effects of the individual variables (concentration of coconut water, temperature and time) and their interactions during the biosynthesis of ZnO-NPs were determined by RSM employing Box-Behnken design. The variables selected were tested by a 17-run experiment and quadratic model was used for the analysis of the results. The accuracy of the model was confirmed by the coefficient of determination ( R 2 ) value of 0.9968. The significance of the regression model was found to be high which is validated by the low probability value of P <; 0.0001. The ZnO-NPs thus synthesised was evaluated for its antimacrofouling activity against mollusks using in-vitro foot-adherence bioassay. The results demonstrated the potential of biosynthesised ZnO-NPs in inhibiting fouling induced due to the test organisms.

Catalytic Characteristics of Metal Catalysts and NitrateSalt of a Tripodal Ligandin a Basic Medium for Postcombustion CO 2 Capture Process

Abstract: Amine-based postcombustion CO2 capture technology has a great potential to control CO2 emissions but is expensive because a huge amount of thermal energy is required for solvent regeneration due to...