RuO₂·nH₂O Nanoparticles Anchored on Carbon Nano-onions: An Efficient Electrode for Solid State Flexible Electrochemical Supercapacitor

A flexible solid state electrochemical capacitor based on hydrous RuO₂ nanoparticles, supported onto the nonporous and highly accessible ion adsorptive carbon nano-onions (CNOs), is fabricated in a novel process of modifying a conducting carbon paper to a flexible conducting substrate, separated with a poly­(vinyl alcohol)/H₂SO₄ gel electrolyte. The sol–gel technique tends to form homogeneously dispersed RuO₂ nanoparticles with the average size of ∼2.3 nm on the positive surface curvatures of multilayer fullerene (CNOs), which helps the high diffusivity of ions in both the aqueous and solid state gel electrolytes. The flexible substrate worked excellently as an electrical conductor as well as a stable mechanical support. This solid state flexible energy storage device showed a maximum energy density of 10.62 Whkg^–1 and a maximum power density of 4.456 kWkg^–1 for the hydrous RuO₂/CNOs nanocomposite with 94.47% cycling stability even after 4000 cycles

Influence of the Crystal Plane Orientation in Enhancing the Electrochemical Performance of a Trication-Substituted Cathode for Li-Ion Batteries

High-voltage spinel cathodes with low nickel are promising candidates for Li-ion batteries owing to their high energy and power density, thermal stability, and eco-friendliness. However, the high operating voltage (∼4.7 V) leads to the decomposition of electrolytes, structural disorder, and deterioration of the cathode–electrolyte interphase (CEI) as well as hinders practical capability. We have synthesized trication-substituted spinel cathode materials with exposed (111) crystal planes and truncated octahedral shapes. These materials have demonstrated high specific discharge capacity and high rate capability up to 1000 cycles with a voltage window of 3.5–5 V. The crystal plane orientation of these materials has been investigated using X-ray diffraction of electrodes and electron microscopic studies and correlated with the electrochemical performance of the surface plane of exposed cathode materials. Among the three synthesized materials, the LMNFA2 cathode has shown a specific discharge capacity of 109.29 mAh g–1 at 1 C after 1000 cycles with a capacity retention of 76.3%, which is nearly equal to the previously reported dual-phase material with the same metal compositions

Formation of the Secondary Phase Domain by Multi-Cation Substitution for the Superior Electrochemical Performance of Spinel Cathodes for High-Voltage Li-Ion Batteries

Disorder-structured spinel oxides are opening frontiers for high-capacity/high-voltage cathodes to meet the challenges of independence on cobalt-containing cathodes toward cheap and sustainable energy storage sources in Li-ion batteries (LIBs). In the present work, a series of Co-free materials: LiMn2‑x‑y‑zNixFeyAlzO4 (x = 0.8–0.5, y = 0.1–0.25, and z = 0.1–0.25) with spinel/rock salt disordered structures are reported. The refinement studies confirmed that the materials synthesized are of mixed phase, and the I311/I400 peaks ratio confirms that the synthesized materials are stable enough for electrochemical applications. This article addresses the influence of the secondary phase on the electrochemical activity and the reduction of the Mn3+ ratio to alleviate the Mn dissolution issue for bettered stability. The optimized LiMnNi0.7Fe0.1Al0.2O4 is appraised as a cathode material in the voltage range between 3.5 and 5 V (vs. Li+/Li) with an initial discharge capacity of 148.7 mA h g–1 at a rate of 1 C. This material showed very good cycling stability with a capacity retention of 79.5% after 1000 cycles. The cyclic voltammetry studies showed that the material can be a potential candidate for 5 V applications

One-pot synthesis of gold nanoparticle/molybdenum cluster/graphene oxide nanocomposite and its photocatalytic activity

International audienceThe paper reports on a facile one-pot synthesis of a tri-component gold nanoparticle/molybdenum cluster/graphene oxide (AuNPs@Mo-GO) nanohybrid composite. The synthetic methodology consists on direct UV irradiation of an aqueous solution containing graphene oxide (GO), Na2[Mo6Br8(N3)6], HAuCl4*3H2O and isopropanol at room temperature in air using a UV fiber lamp. The composite material exhibits very high photocatalytic activity for the degradation of rhodamine B under visible light irradation. The resulting nanohybrid material was characterized using Raman spectroscopy, UV-vis spectrometry, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS)

Biomass-Mediated Synthesis of Cu-Doped TiO2 Nanoparticles for Improved-Performance Lithium-Ion Batteries

Pure TiO2 and Cu-doped TiO2 nanoparticles are synthesized by the biomediated green approach using the Bengal gram bean extract. The extract containing biomolecules acts as capping agent, which helps to control the size of nanoparticles and inhibit the agglomeration of particles. Copper is doped in TiO2 to enhance the electronic conductivity of TiO2 and its electrochemical performance. The Cu-doped TiO2 nanoparticle-based anode shows high specific capacitance, good cycling stability, and rate capability performance for its envisaged application in lithium-ion battery. Among pure TiO2, 3% Cu-doped TiO2, and 7% Cu-doped TiO2 anode, the latter shows the highest capacity of 250 mAh g–1 (97.6% capacity retention) after 100 cycles and more than 99% of coulombic efficiency at 0.5 A g–1 current density. The improved electrochemical performance in the 7% Cu-doped TiO2 is attributed to the synergetic effect between copper and titania. The results reveal that Cu-doped TiO2 nanoparticles might be contributing to the enhanced electronic conductivity, providing an efficient pathway for fast electron transfer

Direct transfer of micro-molded electrodes for enhanced mass transport and water management in PEMFC

Soft lithography technique is used to micropattern the electrodes on the electrolyte membrane of polymer electrolyte fuel cell (PEMFC) in order to alleviate the issues due to poor water management and inadequate reactant distribution in the fuel cell environment. Membrane electrode assembly with the micropatterned electrode has shown an increase in power density at a higher temperature as well as at a higher relative humidity when compared to a flat electrode. Consistency in cell performance is observed in the case of micropatterned electrodes

Glucose-Derived Porous Carbon-Coated Silicon Nanowires as Efficient Electrodes for Aqueous Micro-Supercapacitors

In this study, we report on carbon coating of vertically aligned silicon nanowire (SiNWs) arrays via a simple hydrothermal process using glucose as carbon precursor. Using this process, a thin carbon layer is uniformly deposited on the SiNWs. Under optimized conditions, the coated SiNWs electrode showed better electrochemical energy storage capacity as well as exceptional stability in aqueous system as compared to uncoated SiNWs. The as-measured capacitance reached 25.64 mF/cm² with a good stability up to 25000 charging/discharging cycles in 1 M Na₂SO₄ aqueous solution

High aspect ratio nanoscale multifunctional materials derived from hollow carbon nanofiber by polymer insertion and metal decoration

A novel high aspect ratio material which can simultaneously display multiple functions such as proton and electron conductivity and electrocatalytic activity has been developed by incorporating both platinum nanoparticles and phosphoric acid doped polybenzimidazole along the inner and outer surfaces of a hollow carbon nanofiber

Nanodiamond particles/reduced graphene oxide composites as efficient supercapacitor electrodes

International audienceThe paper reports on the preparation of reduced graphene oxide (rGO) modified with nanodiamond particles composites by a simple solution phase and their use as efficient electrode in electrochemical supercapacitors. The technique relies on heating aqueous solutions of graphene oxide (GO) and nanodiamond particles (NDs) at different ratios at 100 degrees C for 48 h. The morphological properties, chemical composition and electrochemical behavior of the resulting rGO/NDs nanocomposites were investigated using UV/vis spectrometry, Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, transmission electron microscopy (TEM) and electrochemical means. The electrochemical performance, including the capacitive behavior of the rGO/NDs composites were investigated by cyclic voltammetry and galvanostatic charge/discharge curves at 1 and 2 A g(-1) in 1 M H2SO4. The rGO/ND matrix with 10/1 ratio displayed the best performance with a specific capacitance of 186 +/- 10 F g (-1) and excellent cycling stability. (C) 2013 Elsevier Ltd. All rights reserved