Nanostructured (Co, Ni)-Based Compounds Coated on a Highly Conductive Three Dimensional Hollow Carbon Nanorod Array (HCNA) Scaffold for High Performance Pseudocapacitors

The electrochemical performance of the pseudocapacitive materials is seriously limited by poor electron and ions transport. Herein, an advanced integrated electrode has been designed by growing the pseudocapacitive materials, including Co_<i>x</i>Ni_1–<i>x</i>(OH)₂, Co_<i>x</i>Ni_1–<i>x</i>O, and (Co_<i>x</i>Ni_1–<i>x</i>)₉S₈, on a three-dimensional hollow carbon nanorod arrays (HCNA) scaffold. The HCNA scaffold not only can provide large surface area for increasing the mass loading of the pseudocapacitive materials, but also is with good electrical conductivity and hollow structure for facilitating fast electron and electrolyte ions transport, and thus improve the electrochemical performance. Particularly, in comparison with Co_<i>x</i>Ni_1–<i>x</i>(OH)₂ and Co_<i>x</i>Ni_1–<i>x</i>O nanosheets, (Co_<i>x</i>Ni_1–<i>x</i>)₉S₈ nanosheets on the HCNA scaffold exhibit better electrochemical performance. The discharge areal capacitance of the (Co_<i>x</i>Ni_1–<i>x</i>)₉S₈/HCNA electrode can be achieved to 1.32 F cm^–2 at 1 mA cm^–2, ∼1.5 times as that of the Co_<i>x</i>Ni_1–<i>x</i>(OH)₂/HCNA electrode. The rate capability performance is also improved. 71.8% of the capacitance is retained with increasing the discharge current density from 1 to 10 mA cm^–2, in contrast to ∼59.9% for the Co_<i>x</i>Ni_1–<i>x</i>(OH)₂/HCNA electrode. Remarkably, the cycling stability is significantly enhanced. ∼111.2% of the initial capacitance is gained instead of decaying after the 3000 cycles at 8 mA cm^–2, while there is ∼11.5% loss for the Co_<i>x</i>Ni_1–<i>x</i>(OH)₂/HCNA electrode tested under the same condition. Such good electrochemical performance can be ascribed by that (Co_<i>x</i>Ni_1–<i>x</i>)₉S₈ exhibits the similar energy storage mechanism as Co_<i>x</i>Ni_1–<i>x</i>(OH)₂ and Co_<i>x</i>Ni_1–<i>x</i>O, and more importantly, is with better electrical conductivity

Design Hierarchical Electrodes with Highly Conductive NiCo₂S₄ Nanotube Arrays Grown on Carbon Fiber Paper for High-Performance Pseudocapacitors

We report on the development of highly conductive NiCo₂S₄ single crystalline nanotube arrays grown on a flexible carbon fiber paper (CFP), which can serve not only as a good pseudocapacitive material but also as a three-dimensional (3D) conductive scaffold for loading additional electroactive materials. The resulting pseudocapacitive electrode is found to be superior to that based on the sibling NiCo₂O₄ nanorod arrays, which are currently used in supercapacitor research due to the much higher electrical conductivity of NiCo₂S₄. A series of electroactive metal oxide materials, including Co_<i>x</i>Ni_1–<i>x</i>(OH)₂, MnO₂, and FeOOH, were deposited on the NiCo₂S₄ nanotube arrays by facile electrodeposition and their pseudocapacitive properties were explored. Remarkably, the as-formed Co_<i>x</i>Ni_1–<i>x</i>(OH)₂/NiCo₂S₄ nanotube array electrodes showed the highest discharge areal capacitance (2.86 F cm^–2 at 4 mA cm^–2), good rate capability (still 2.41 F cm^–2 at 20 mA cm^–2), and excellent cycling stability (∼4% loss after the repetitive 2000 cycles at a charge–discharge current density of 10 mA cm^–2)

Vertically Aligned Heteroatom Doped Carbon Nanosheets from Unzipped Self-Doped Carbon Tubes for High Performance Supercapacitor

A common but important problem of carbon-based supercapacitors unresolved is the difficulty of achieving high specific capacitance over a wide voltage window when the electrodes are assembled into devices. Adjusting the structure of carbon materials is expected to tune the electrode potential and the surface charge density of the electrode materials, and thus further enhance the energy density of carbon-based supercapacitors. Herein, an efficient surface charge control strategy was developed to remarkably enhance the energy density of porous N, O codoped vertically aligned carbon nanosheets (VACNs) based solid-state symmetric supercapacitors through unzipping N, O codoped carbon tubes by transition metal atoms. Originating from the synergetic effect of vertically aligned structure and the doped N, O atoms, the assembled solid-state symmetric supercapacitor based on N, O codoped VACNs electrodes exhibits excellent electrochemical performance. The synthesis strategy may enlighten the design and fabrication of well-defined carbon-based nanomaterials that have potential applications in energy storage and other area

Palladium Nanoparticles Anchored on Amine-Functionalized Silica Nanotubes as a Highly Effective Catalyst

The catalytic performance of supported heterogeneous catalysts is mainly dependent on their constitutive components including active species and supports. Therefore, the design and development of effective catalysts with synergistic enhanced effect between active sites and supports is of great significance. A facile in situ reduction approach to prepare amine-functionalized silica nanotubes (ASNTs)-supported Pd (ASNTs@Pd) composite catalyst is demonstrated in this article. Benefiting from the intrinsic physical and chemical properties of the ASNTs support and deposited Pd nanoparticles (NPs), the as-prepared ASNTs@Pd catalyst exhibits superior catalytic activity, stability, and reusability toward nitroarene reduction reactions. For catalytic reduction of 4-nitrophenol, the turnover frequency (TOF) is as high as 313.5 min^–1, which is much higher than that of commercial Pd/C (5.0 wt %) and many noble-metal based catalysts reported in the last 5 years. In addition, a high TOF of 57.4 min^–1 was also realized by ASNTs@Pd catalyst for the Suzuki coupling reaction