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Sodium-ion hybrid supercapacitors are potential energy-storage devices and have recently received enormous interest. However, the development of cathode materials and the use of nonaqueous electrolyte remain a great challenge. Hence, aqueous Na-ion hybrid supercapacitors based on a three-dimensional network of NaMnO were developed. The cathode material was synthesized by the electro-oxidation of potassium manganese hexacyanoferrate nanocubes. The oxidized compound was confirmed to be Na MnO by various physical characterization methods. Manganese dioxide is a well-characterized material for aqueous asymmetric pseudocapacitors, but its usage at high operating voltages is limited due to the electrochemical stability of water. Nevertheless, high-potential and high-performance aqueous supercapacitors exhibiting a cell potential of 2.7 V were developed. Further, the practical applicability of an asymmetric supercapacitor based on NaMnO (cathode) and reduced graphene oxide (anode) was demonstrated by powering a 2.1 V red LED.

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We present a facile and simple method to synthesize a thin layer of platinum on gold as Au@Pt core−shell nanoparticles on the surface of reduced graphene oxide (rGO) via Cu under potential deposition (UPD) followed by galvanic Pt replacement reaction. The difference in the reduction potential is the driving force for the reaction where Pt 4+ ions reduced and deposited simultaneously on the surface of Au by replacing the Cu surface. The as synthesized catalyst was characterized by scanning electron microscope (SEM), energy dispersive X-ray mapping analysis (EDAX), high resolution transmission electron microscope (HRTEM), High angle annular dark-field scanning/transmission electron microscopy (STEM-HAADF), X-ray diffraction (XRD), Raman spectroscopy and electrochemical studies. It exhibits an excellent electrocatalytic activity towards methanol and ethanol oxidation in alkaline medium due to enhanced mass and specific activities. Galvanic replacement method paves an important role in the architecture of a thin layer of Pt on Au surface. On the other hand, rGO surface acts as a solid

The accurate detection of dopamine (DA) levels in biological samples such as human serum and urine are essential indicators in medical diagnostics. In this work, we describe the preparation of chitosan (CS) biopolymer grafted graphite (GR) composite for the sensitive and lower potential detection of DA in its sub micromolar levels. The composite modified electrode has been used for the detection of DA in biological samples such as human serum and urine. The GR-CS composite modified electrode shows an enhanced oxidation peak current response and low oxidation potential for the detection of DA than that of electrodes modified with bare, GR and CS discretely. Under optimum conditions, the fabricated GR-CS composite modified electrode shows the DPV response of DA in the linear response ranging from 0.03 to 20.06μM. The detection limit and sensitivity of the sensor were estimated as 0.0045μM and 6.06μA μM(-1)cm(-2), respectively.