In this study, we adopted a simple method to synthesize a graphene-like-structured nanoporous carbon using a jute stick as a carbon precursor and studied the electrochemical properties for supercapacitors. The synthesized nanoporous carbon is composed of a graphene sheet-like network and amorphous carbon, and the ratio between these two components is tuned by the activation temperature. As the activation temperature is increased, the amorphous carbon is converted into a stable graphene-like network with a high specific surface area of 2396 m2/g, with a graphene sheet-like morphology and a highly ordered graphitic sp2 carbon. For supercapacitor application, the nanoporous carbon is studied in aqueous as well as organic electrolytes, and the material shows excellent electrochemical performance in both the cases. It exhibited a high specific capacitance of 282 F/g and shows excellent rate capability with almost 70% capacitance retention at high current rates. Furthermore, the assembled symmetric supercapacitor displays a remarkable energy density of 20.6 W h kg–1 at a high power density of 33 600 W kg–1, and the benchmark studies revealed that the nanoporous carbon developed in the present study is better than the commercially available supercapacitive carbon (YP-50 F). A cylindrical supercapacitor device of capacitance 20 F with 2.7 V was fabricated using the nanoporous carbon electrode and tested for running practical devices. The excellent electrochemical performance of the electrode material can be attributed to the high electrical conductivity of the ordered graphene network coupled with high specific surface area and optimum pore size distribution of nanoporous carbon. These results demonstrate a facile, low-cost, and eco-friendly design of materials for energy storage applications.

The room temperature stable P3 type Na 0.6 Ni 0.25 Mn 0.5 Co 0.25 O 2 phase was studied as an interaction material for Na ion batteries. The phase was synthesized by mixed hydroxide coprecipitation method followed by heating at 750 8C in air. The phase purity was analyzed by means of Rietveld refinement using GSAS software. X-ray photoelectron spectroscopy (XPS) analysis showed that Co, and Mn are in oxidation states of 3 + and 4 + , respectively, and Ni is in 2 + and 3 + oxidation states. The electrochemical properties of this layered material as a cathode delivered the reversible discharge capacity of 105 and 130 mAh/g at C/10 rate in the voltage window of 1.5-3.6 and 1.5-4.0 V vs. Na + /Na, respectively. The good capacity retention and nearly 99 % of coloumbic efficiency was observed. The Na insertion and de-insertion was occurred by reversible phase transitions as evidenced by ex-situ powder X-ray diffration. With increasing cutoff voltage to 4.4 V, the ex-situ powder X-ray diffration pattern indicated that the existence of P3 phase at high Na de-insertion.[a] S. Maddukuri, Prof.

Luminescent polymer based metallogels have gained considerable interest due to their wide range of applications in the fields of tissue engineering, drug delivery, sensing, and optical systems. One of the...

Electrochemical Li insertion/de‐insertion studies were performed on monoclinic W2O3(PO4)2 in the voltage window of 3.5‐1.8 V vs. Li+/Li. At C/5 rate, 2.0 Li+ ions/f.u (90 mAh g−1 ) are inserted in the lattice during first discharge and 1.75 Li+ ions (75 mAh g−1 ) are de‐inserted during first charge with a reversible two phase process. A stable discharge capacity of 65 and 55 mAh g−1 were obtained in the voltage window of 3.5‐1.8 V and 3.5‐2.25 V at C/5 rate, respectively. In case of discharge to 1.4 V, the initial discharge capacity of 200 mAh g−1 was obtained with insertion of 4.5 Li+ ions. The irreversible phase change was observed on charge with 11th cycle discharge capacity of 50 mAh g−1. The X‐ray photo electron spectroscopy analysis shows the feasibility of W6+/ W5+ and W5+/W4+ redox couples vs. Li+/Li. The sodium ion insertion into the crystal lattice leads to poor reversibility with delivered discharge capacity of 30 mAh g−1 at the end of 25 cycles at C/5 rate in the voltage window of 1.2‐3.0 V vs. Na+/Na. Ex‐situ X‐ray diffraction patterns indicate that Li insertion/de‐insertion was possible in the parent phase. Formation of a new phase was observed which was also amenable for facile insertion/de‐insertion of Li. Both the parent as well as the new phase undergoes reversible phase transitions during the process of insertion/de‐insertion of Li in the voltage window of 1.8‐3.5 V.

Current technology of lighting is Solid state lighting using LED's (SSL-LED). The aim of the present study is to find the critical concentration of Eu 2+ for high emission intensity and also the role of Ce 3+ co-doping on the absorption and emission properties in the host BaMgSiO 4 . Photoluminescence emission of Eu 2+ in BaMgSiO 4 when excited with 370 nm shows a broad band in the region 450 to 550 nm with a maximum at 502 nm and a shoulder at ∼480 nm and one more band at ~ 400nm. The three emissions are due to Eu 2+ in three different Ba sites in the lattice. Studies on Ba 1-x Eu x MgSiO 4 [x = 0.0025 -0.1 in steps of 0.0025] show that the emission intensity is maximum for x = 0.075 and a decrease in emission intensity is observed for higher x values. Ce 3+ luminescence is studied for the first time in BaMgSiO 4 . Ce 3+ emission occurs as a broad band with maximum at 430 nm when excited with 356 nm. The Eu 2+ excitation that occurs in the region 250 -420 nm covers both the Ce 3+ absorption and emission. Hence Ce 3+ to Eu 2+ energy transfer is possible in BaMgSiO 4 . In the case of Ba 0.99-x Eu 0.01 Ce x MgSiO 4 [ x = 0.0025 -0.1 ], it is observed that the emission intensity of Eu 2+increases with increasing Ce 3+ content up to 0.01. This result proves the energy transfer from Ce 3+ to Eu 2+ . Thus, the co-doping of Ce 3+ also enhances the absorption of Eu 2+ in the near UV to blue region where the LED emission occurs. BaMgSiO 4 :Eu 2+ , Ce 3+ with bright green emission can find potential application as a green phosphor for SSL-LED technology.

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