The demand for advanced energy storage devices such as supercapacitors and lithium‐ion batteries has been increasing to meet the application requirements of hybrid vehicles and renewable energy systems. A major limitation of state‐of‐art supercapacitors lies in their relatively low energy density compared with lithium batteries although they have superior power density and cycle life. Here, we report an additive‐free, nano‐architectured nickel hydroxide/carbon nanotube (Ni(OH)2/CNT) electrode for high energy density supercapacitors prepared by a facile two‐step fabrication method. This Ni(OH)2/CNT electrode consists of a thick layer of conformable Ni(OH)2 nano‐flakes on CNT bundles directly grown on Ni foams (NFs) with a very high areal mass loading of 4.85 mg cm−2 for Ni(OH)2. Our Ni(OH)2/CNT/NF electrode demonstrates the highest specific capacitance of 3300 F g−1 and highest areal capacitance of 16 F cm−2, to the best of our knowledge. An asymmetric supercapacitor using the Ni(OH)2/CNT/NF electrode as the anode assembled with an activated carbon (AC) cathode can achieve a high cell voltage of 1.8 V and an energy density up to 50.6 Wh/kg, over 10 times higher than that of traditional electrochemical double‐layer capacitors (EDLCs).

We have fabricated ultrathin lead films on silicon substrates with atomic-scale control of the thickness over a macroscopic area. We observed oscillatory behavior of the superconducting transition temperature when the film thickness was increased by one atomic layer at a time. This oscillating behavior was shown to be a manifestation of the Fabry-Perot interference modes of electron de Broglie waves (quantum well states) in the films, which modulate the electron density of states near the Fermi level and the electron-phonon coupling, which are the two factors that control superconductivity transitions. This result suggests the possibility of modifying superconductivity and other physical properties of a thin film by exploiting well-controlled and thickness-dependent quantum size effects.

Hierarchically porous Ni-Co oxide powder is successfully synthesized by a facile chemical bath deposition method. The structure and composition of Ni-Co oxide are confirmed by transmission electron microscopy and energy dispersive X-ray analysis. Scanning electron microscopy characterization indicates that the Ni-Co oxide has architecture of numerous microflowers with porous flakes. The pseudocapacitive behavior of the Ni-Co oxide powder is investigated by cyclic voltammgrams (CVs) and galvanostatic chargedischarge tests in alkali solution. The Ni-Co oxide shows a good reversibility with a high specific capacitance (834.93 Fg −1 at 1 mVs −1 scan rate). This active material was also used to manufacture a Ni-Co oxide//AC (Active Carbon) asymmetric supercapacitor. The Ni-Co oxide//AC asymmetric supercapacitor shows not only a high specific capacitance (60 Fg −1 with 1 mVs −1 scan rate), but also a high reversibility where its specific capacitance remains at 37 Fg −1 at a high current density of 20 mAcm −2 .

A simple method was developed to prepare ultra‐low Pt loading membrane electrode assembly (MEA) using vertically aligned carbon nanotubes (VACNTs) as highly ordered catalyst support for PEM fuel cells application. In the method, VACNTs were directly grown on the cheap household aluminum foil by plasma enhanced chemical vapor deposition (PECVD), using Fe/Co bimetallic catalyst. By depositing a Pt thin layer on VACNTs/Al and subsequent hot pressing, Pt/VACNTs can be 100% transferred from Al foil onto polymer electrolyte membrane for the fabrication of MEA. The whole transfer process does not need any chemical removal and destroy membrane. The PEM fuel cell with the MEA fabricated using this method showed an excellent performance with ultra‐low Pt loading down to 35 μg cm−2 which was comparable to that of the commercial Pt catalyst on carbon powder with 400 μg cm−2. To the best of our knowledge, for the first time, we identified that it is possible to substantially reduce the Pt loading one order by application of order‐structured electrode based on VACNTs as Pt catalysts support, compared with the traditional random electrode at a comparable performance through experimental and mathematical methods.

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NiS nanowire arrays doped with vanadium(V) are directly grown on nickel foam by a facile one-step hydrothermal method. It is found that the doping can promote the formation of NiS nanowires at a low temperature. The doped nanowires show excellent electrocatalytic performance toward hydrogen evolution reaction (HER), and outperform pure NiS and other NiS-based compounds. The stability test shows that the performance of V-doped NiS nanowires is improved and stabilized after thousands of linear sweep voltammetry test. The onset potential of V-doped NiS nanowire can be as low as 39 mV, which is comparable to platinum. The nanowire has an overpotential of 68 mV at 10 mA cm, a relatively low Tafel slope of 112 mV dec, good stability and high Faradaic efficiency. First-principles calculations show that the V-doping in NiS extremely enhances the free carrier density near the Fermi level, resulting in much improved catalytic activities. We expect that the doping can be an effective way to enhance the catalytic performance of metal disulfides in hydrogen evolution reaction and V-doped NiS nanowire is one of the most promising electrocatalysts for hydrogen production.

A fl exible solid-state asymmetric supercapacitor based on bendable fi lm electrodes with 3D expressway-like architecture of graphenes and "hard nano-spacer" is fabricated via an extended fi ltration assisted method. In the designed structure of the positive electrode, graphene sheets are densely packed, and Ni(OH) 2 nanoplates are intercalated in between the densely stacked graphenes. The 3D expressway-like electrodes exhibit superior supercapacitive performance including high gravimetric capacitance (≈573 F g −1 ), high volumetric capacitance (≈655 F cm −3 ), excellent rate capability, and superior cycling stability. In addition, another hybrid fi lm of graphene and carbon nanotubes (CNT) is fabricated as the negative electrodes for the designed asymmetric device. In the obtained graphene@CNT fi lms, CNTs served as the hard spacer to prevent restacking of graphene sheets but also as a conductive and robust network to facilitate the electrons collection/transport in order to fulfi ll the demand of high-rate performance of the asymmetric supercapacitor. Based on these two hybrid electrode fi lms, a solid-state fl exible asymmetric supercapacitor device is assembled, which is able to deliver competitive volumetric capacitance of 58.5 F cm −3 and good rate capacity. There is no obvious degradation of the supercapacitor performance when the device is in bending confi guration, suggesting the excellent fl exibility of the device.

Using a low temperature growth method, we have prepared atomically flat Pb thin films over a wide range of film thickness on a Si-(111)-7 x 7 surface. The Pb film morphology and electronic structure are investigated in situ by scanning tunneling microscopy and angle-resolved photoemission spectroscopy. Well-defined and atomic-layer-resolved quantum-well states of the Pb films are used to determine the band structure and the electron-phonon coupling constant (lambda) of the films. We found an oscillatory behavior of lambda with an oscillation periodicity of two atomic layers. Almost all essential features in the Pb/Si(111) system, such as the growth mode, the oscillatory film stability, and the 9 monolayer envelope beating pattern, can be explained by our results in terms of the electron confinement in Pb films.