Yun Ju Hwang

A facile one-pot green synthesis of reduced graphene oxide and its composites for non-enzymatic hydrogen peroxide sensor applications

A simple, environmental benign, time and cost-efficient green approach has been proposed for the reduction of graphene oxide (GO) and the synthesis of reduced GO (rGO)/mono and bimetallic composites using Azadirachta indica extract. The high crystallinity and face-centred-cubic structure of monometallic silver (Ag) and bimetallic silver–gold (Ag–Au) nanoparticles anchored over rGO were determined from the X-ray diffraction patterns. The functional groups involved in the reduction of GO and metallic precursors were identified by the Fourier transform–infrared spectroscopic technique. The obtained morphological images revealed a homogeneous distribution of spherical shaped Ag/Ag–Au nanoparticles with a narrow size distribution anchored over the rGO sheets. The prepared nanostructures exhibited significant electrocatalytic activities towards the reduction of hydrogen peroxide (H2O2), leading to a non-enzymatic electrochemical sensor with a prompt amperometric response. The non-enzymatic sensor responded linearly (R2 = 0.9970) to the concentration of H2O2 over a range of 0.1 to 5 mM with a low level detection limit of 1 μM.

A comparative study of nanostructured α and δ MnO2 for lithium oxygen battery application

α- and δ-MnO2 nanomaterials with different morphology like urchins and flowers are successfully synthesized by a low temperature hydrothermal synthesis. The prepared nanostructures were applied as electrocatalysts for air cathodes in Li air batteries. The synthesized materials possess high electrocatalytic activity and the MnO2 catalysed electrodes doubled the initial cycling capacity of the Li air cells without any catalysts. We also observed reduced over potential and upon cycling with limited capacity, a very stable performance was obtained.

Lithium Air Battery: Alternate Energy Resource for the Future

ABSTRACT: Increasing demand of energy, the depletion of fossil fuel reserves, energy security and the climatechange have forced us to look upon alternate energy resources. For today’s electric vehicles that runon lithium-ion batteries, one of the biggest downsides is the limited range between recharging. Overthe past several years, researchers have been working on lithium–air battery. These batteries couldsignificantly increase the range of electric vehicles due to their high energy density, which couldtheoretically be equal to the energy density of gasoline. Li-air batteries are potentially viable ultra-high energy density chemical power sources, which could potentially offer specific energies up to3000 Whkg −1 being rechargeable. This paper provides a review on Lithium air battery as alternateenergy resource for the future.Keywords: Porous air cathode, Catalyst, Lithium air battery, Electrolyte, Energy storage Received March 3, 2012 : Accepted March 27, 2012 1. Introduction Depletion of global fossil oil resources has been thetheme topic of the world economic and political cir-cles over the past decades. How the alternatives can beexploitable, while being economically cost-effective,are the key factors in coming up with conclusions andmaking decision on the part of consumers. Over thepast several decades, the consumer countries havebeen weighing up the use of other resources, or substi-tutes, such as solar, water, wind, nuclear etc. Althoughhuge research works have been done, it sounds a seri-ous step has not been taken yet; mainly because therehave been gigantic amount of this noble energy car-rier, namely the oil, comparing with other substituteresources being highly cost effective. So all this havemade weak incentives for the use of other resources.But over the past several years, researchers have beenworking on an alternative battery called a lithium–airbattery which gives the energy density almost equiva-lent to the gasoline. By the use of this battery in elec-tric vehicles just by changing the electrode in thelithium ion to air, it would be possible for a battery ofthe same size and weight to hold up to 10 times moreenergy-potentially harnessing the same energy den-sity as petrol. Such lithium–air batteries have an anodemade of lithium which is oxidized by the oxygen cath-ode (drawn from environment air), releasing energy.Pumping electricity into the battery reverses the proce-dure, pushing out the oxygen and leaving the lithium.In 1996, Abraham and Jiang

Influence of Solvents on the Structural and Electrochemical Properties of Li [ Li0.2Ni0.1Co0.2Mn0.5 ] O2 Prepared by a Solvothermal Reaction Method

Solid solutions of Li[Li 0 . 2 N 0 . 1 Co 0 . 2 Mn 0 . 5 ]O 2 were prepared by solvothermal reaction with three different solvents, namely, methanol, ethanol, and 1-propasol. The prepared compounds were subjected to X-ray diffraction (XRD), Raman, Fourier transform infrared, and charge-discharge studies. XRD studies revealed that the prepared compounds are of layered structure with space group R3m. The sample which was prepared using 1-propanol as solvent delivered the highest discharge capacity of 205 mAh/g. The electrochemical and structural properties of the prepared compounds are influenced by the physical properties of the solvents.