Enhancement of hydrogen evolution reaction by Pt nanopillar-array electrode in alkaline media and the effect of nanopillar length on the electrode efficiency

Pt nanopillar-array 3D electrodes with nanopillar length of 150, 450 and 900 nm and nanopillar density of ~10⁹ cm⁻² were fabricated. Their catalytic activity for hydrogen evolution reaction (HER) was evaluated by linear sweep voltammetry and electrochemical impedance spectroscopy. In comparison with straightly electrodeposited black Pt film and forged Pt sheet electrodes, the HER current density has been significantly improved by the nanopillar-array architecture. The overpotential of HER at current density of 10 mA cm-2 at 26 °C is as low as 78 mV, lower than the black Pt film of 107 mV and the Pt sheet of 174 mV. The improvement of HER is ascribed to the low charge transfer resistance of the 3D electrode and the high desorption capability of hydrogen bubbles at the nanotips. Interestingly, the nanopillar-array 3D electrode has an optimal nanopillar length for HER. The mechanisms for the optimal nanopillar length were investigated here.     

Constructing 3D honeycomb-like CoMn2O4 nanoarchitecture on nitrogen-doped graphene coating Ni foam as flexible battery-type electrodes for advanced supercapattery

Reasonable structural design is significant to enable the performance in advanced energy storage devices. Herein, a 3D honeycomb-like CoMn₂O₄ nanoarchitecture (CMO) on nitrogen-doped graphene (NG) coating Ni foam (denoted as Ni/NG/CMO) flexible battery-type electrode was prepared by a facile two-step hydrothermal strategy. The honeycomb-like CoMn₂O₄ arrays not only provide abundant active sites but can also be closely combined with the Ni foam/NG substrate, which enables high reversible capacity and good cycle stability during the long cycles. Benefiting from the compositional features and 3D honeycomb-like nanoarchitecture, the Ni/NG/CMO composite electrode displays improved electrochemical performance with remarkable specific capacity of 527.0C g⁻¹ at a current density of 1 A g⁻¹, outstanding rate capability (338.6C g⁻¹ even at 20 A g⁻¹). In addition, a flexible binder-free supercapattery device has been assembled with Ni/NG/CMO as positive electrode and 3D Ni/NG as negative electrode. Such a supercapattery delivers a high energy density of 44.1 Wh·kg⁻¹ at 992.6 W kg⁻¹, 20.3 Wh·kg⁻¹ at 12430.0 W kg⁻¹ as well as excellent cycling durability. The 3D honeycomb-like Ni/NG/CMO could be considered as an advanced flexible battery-type material for high capacity and energy density fields.     

Tailoring surface capacitance of Ti3C2Tx-PANI@CNTs nanoarchitecture for tunable energy storage and high-performance micro-supercapacitor

Transition metal carbide or nitride (MXenes), as a novel family of two-dimensional materials, exhibit huge potential for electrochemical energy storage thanks to their excellent electrical conductivity, fast ion diffusion rate, high electrochemical activity and good hydrophilicity. However, the electrochemical properties of MXenes tend to be deteriorated due to the self-restacking phenomenon. Herein, by self-assembly, a unique three-dimensional (3D) Ti₃C₂T_x-PANI@CNTs (TPCs) nanoarchitecture was constructed. Through optimizing structures, the surface capacitance of TPCs can be tailored to tune energy storage. The optimal specific capacitance up to 431.9 F/g was achieved under 1 A/g. Further, the TPCs nanoarchitectures were prepared into self-standing films with excellent mechanical properties and micro-supercapacitors (MSCs) in various shapes were manufactured based on the film. The MSCs demonstrate competitive energy storage capacities, obtaining an areal capacitance of 78.2 mF/cm² and energy density of up to 2.72 μWh/cm², still maintain excellent performance under harsh bending. The strategy for constructing 3D nanoarchitectures and further manufacturing MSCs can inspire the design of novel electrode materials and devices to advance the development in the field of energy storage.     

Cost effective and reliable electric wire filaments coated with nanofabricated and sintered superconductive ceramics

Abstract

This paper reports the major results of research and development of thermochemically nanofabricated high temperature superconducting (HTS) ceramic leads and multifilament HTS YBa₂Cu₃O_7–x (HTS-YBCO) electric wire. Advanced scientific features of the created ceramic engineering processing based on ceramic polymer (silicone) nanotechnology, including ceramic coating on continuous metal filaments, are discussed. Thermochemical nanofabrication of the honeycomb-like nanoarchitecture resulted in intergrain superconductivity of the fully dense sintered YBCO macroceramics, which is close to the inner grain superconductivity of the initial YBCO particles. The developed multifilament HTS-YBCO wire is cost effective, reliable, flexible and as workable as copper wire, but conducts ～100 times more electricity with insignificant heat losses.     

Growth of 3-D flower/grass-like metal oxide nanoarchitectures based on catalyst-assisted oxidation method

Cu₂O grass-like and ZnO flower-like nanoarchitectures were fabricated directly on Cu powders and Zn powders using a novel thermal oxidation stress-induced (TOS) method based on catalyst assistance at a low temperature of 150°C under moderate humid atmosphere. The experiments of Al powder were also carried out based on TOS method. Overlapping migration (OLM) of Cu and Zn atoms and toothpaste squeezing migration (TSM) of Al atoms caused by different atom densities in metal oxide materials were studied.

PACS

81. Materials science; 81.07.-b Nanoscale materials and structures: fabrication and characterization; 81.16.Hc Catalytic methods     

Cell architecture for nanoelectronic design

Nanotechnology research has already proved and implemented several nanoscale devices. However, due to high defect ratios, large parameter variability and reduced noise margins, special architectures are needed to build reliable mid/large nanocircuits. Up to date several architectures have been proposed to design circuits in the nanoscale, but they do not consider the entire nanoscale environment. In this work, we propose and analyze a cell architecture based on the averaging of multiple nanodevices which is capable of alleviating the three main problems of the nanodevices at the gate level (internal noise, device parameter variation and defects). The proposed structure has a low implementation complexity which further reduces the fabrication defects. Using this cell architecture we present 2 and 3-input NAND gates showing their output response and error probabilities. Finally, we show that it is possible to improve the cell error tolerance by taking advantage of interferences among nanodevices which reduces the standard deviation by a factor larger than .