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Laursen A.B.,Center for Individual Nanoparticle Functionality | Vesborg P.C.K.,Center for Individual Nanoparticle Functionality | Chorkendorff I.,Center for Individual Nanoparticle Functionality
Chemical Communications | Year: 2013

This work describes a highly active and stable acid activated carbon fibre and amorphous MoSx composite hydrogen evolution catalyst. The increased electrochemical-surface area is demonstrated to cause increased catalyst electrodeposition and activity. These composite electrodes also show an improved stability towards the mechanical degradation of the MoSx catalyst. This journal is © The Royal Society of Chemistry.


Wang F.,South University of Science and Technology of China | Wang F.,Technical University of Denmark | Hansen O.,Technical University of Denmark | Hansen O.,Center for Individual Nanoparticle Functionality
Sensors and Actuators, A: Physical | Year: 2014

In this paper, we report on an electrostatic energy harvester with an out-of-the-plane gap closing scheme. Using advanced MEMS technology, energy harvesting devices formed by a four wafer stack are batch fabricated and fully packaged at wafer scale. A spin coated CYTOP polymer is used both as an electret material and an adhesive layer for low temperature wafer bonding. The overall size of the device is about 1.1 cm × 1.3 cm. At an external load resistance of 13.4 MΩ, a power output of 0.15 μW is achieved when vibration at an acceleration amplitude of 1 g (∼9.8 m/s2) is applied at a low frequency of 96 Hz. The frequency response of the device is also measured and a broader bandwidth is observed at higher acceleration amplitude. © 2014 Elsevier B.V. All rights reserved.


Wang F.,Technical University of Denmark | Hansen O.,Technical University of Denmark | Hansen O.,Center for Individual Nanoparticle Functionality
2013 Transducers and Eurosensors XXVII: The 17th International Conference on Solid-State Sensors, Actuators and Microsystems, TRANSDUCERS and EUROSENSORS 2013 | Year: 2013

In this paper, we report on an electrostatic energy harvester with an out-of-the-plane gap closing scheme. Using advanced MEMS technology, energy harvesting devices with a four wafer stack are batch fabricated and fully packaged at wafer scale. CYTOP polymer is used both as an electret material and an adhesive layer for low temperature wafer bonding. The overall size of the device is about 1.1×1.3 cm2. With an external load of 13.4 MΩ, a power output of 0.15 μW is achieved when vibration at an acceleration amplitude of 1 g (9.8 m/s2) is applied at a low frequency of 96 Hz. The frequency response of the device is also measured and a broader bandwidth is observed at higher acceleration amplitude. © 2013 IEEE.


Paoli E.A.,Center for Individual Nanoparticle Functionality | Masini F.,Center for Individual Nanoparticle Functionality | Frydendal R.,Center for Individual Nanoparticle Functionality | Deiana D.,Center for Electronic Nanoscopy | And 6 more authors.
Chemical Science | Year: 2015

Oxygen evolution was investigated on model, mass-selected RuO2 nanoparticles in acid, prepared by magnetron sputtering. Our investigations include electrochemical measurements, electron microscopy, scanning tunneling microscopy and X-ray photoelectron spectroscopy. We show that the stability and activity of nanoparticulate RuO2 is highly sensitive to its surface pretreatment. At 0.25 V overpotential, the catalysts show a mass activity of up to 0.6 A mg-1 and a turnover frequency of 0.65 s-1, one order of magnitude higher than the current state-of-the-art. This journal is © The Royal Society of Chemistry.


Mei B.,Center for Individual Nanoparticle Functionality | Permyakova A.A.,Center for Individual Nanoparticle Functionality | Frydendal R.,Center for Individual Nanoparticle Functionality | Bae D.,Center for Individual Nanoparticle Functionality | And 7 more authors.
Journal of Physical Chemistry Letters | Year: 2014

Sputter deposition of 50 nm thick NiO films on p+-n-Si and subsequent treatment in an Fe-containing electrolyte yielded highly transparent photoanodes capable of water oxidation (OER) in alkaline media (1 M KOH) with high efficiency and stability. The Fe treatment of NiO thin films enabled Si-based photoanode assemblies to obtain a current density of 10 mA/cm2 (requirement for >10% efficient devices) at 1.15 V versus RHE (reversible hydrogen electrode) under red-light (38.6 mW/cm2) irradiation. Thus, the photoanodes were harvesting ∼80 mV of free energy (voltage), which places them among the best-performing Si-based photoanodes in alkaline media. The stability was proven by chronoamperometry at 1.3 V versus RHE for 300 h. Furthermore, measurements with electrochemical quartz crystal microbalances coupled with ICP-MS showed minor corrosion under dark operation. Extrapolation of the corrosion rate showed stability for more than 2000 days of continuous operation. Therefore, protection by Fe-treated NiO films is a promising strategy to achieve highly efficient and stable photoanodes. © 2014 American Chemical Society.


Kehres J.,Center for Individual Nanoparticle Functionality | Jakobsen J.G.,Haldor Topsøe | Andreasen J.W.,Technical University of Denmark | Wagner J.B.,Technical University of Denmark | And 5 more authors.
Journal of Physical Chemistry C | Year: 2012

Combined in situ small- and wide-angle X-ray scattering (SAXS/WAXS) studies were performed in a new laboratory setup to investigate the dynamical properties of a ruthenium/spinel (Ru/MgAl 2O 4) catalyst, w(Ru) = 4 wt %, during the reduction and subsequent dry methane reforming. The Ru particles in the fresh catalyst sample were found to be partially oxidized. High-resolution transmission electron microscopy (HRTEM) indicated a coexistence of pure Ru and RuO 2 nanoparticles. Reduction in hydrogen occurred at a temperature between 373 and 393 K. The mean particle diameter as refined from SAXS of the size regime attributed to scattering from Ru/RuO 2-particles decreases slightly by about 0.2 nm during the reduction. Dry methane reforming experiments were performed in a temperature interval from 723 to 1023 K by applying a gas mixture of carbon dioxide and methane in molar ratio of 3:1. The catalyst did not show any deactivation during the experiment of overall 32 h, indicated by stable turnover frequencies for methane. The mean Ru-particle diameter remained constant during the dry methane reforming experiments, revealing a high sintering stability of the Ru/MgAl 2O 4 catalyst. © 2012 American Chemical Society.


Roske C.W.,Pennsylvania State University | Popczun E.J.,Pennsylvania State University | Seger B.,Center for Individual Nanoparticle Functionality | Read C.G.,Pennsylvania State University | And 10 more authors.
Journal of Physical Chemistry Letters | Year: 2015

The electrocatalytic performance for hydrogen evolution has been evaluated for radial-junction n+p-Si microwire (MW) arrays with Pt or cobalt phosphide, CoP, nanoparticulate catalysts in contact with 0.50 M H2SO4(aq). The CoP-coated (2.0 mg cm-2) n+p-Si MW photocathodes were stable for over 12 h of continuous operation and produced an open-circuit photovoltage (Voc) of 0.48 V, a light-limited photocurrent density (Jph) of 17 mA cm-2, a fill factor (ff) of 0.24, and an ideal regenerative cell efficiency (IRC) of 1.9% under simulated 1 Sun illumination. Pt-coated (0.5 mg cm-2) n+p-Si MW-array photocathodes produced Voc = 0.44 V, Jph = 14 mA cm-2, ff = 0.46, and = 2.9% under identical conditions. Thus, the MW geometry allows the fabrication of photocathodes entirely comprised of earth-abundant materials that exhibit performance comparable to that of devices that contain Pt. © 2015 American Chemical Society.


PubMed | Center for Individual Nanoparticle Functionality
Type: Journal Article | Journal: Chemical communications (Cambridge, England) | Year: 2013

This work describes a highly active and stable acid activated carbon fibre and amorphous MoS(x) composite hydrogen evolution catalyst. The increased electrochemical-surface area is demonstrated to cause increased catalyst electrodeposition and activity. These composite electrodes also show an improved stability towards the mechanical degradation of the MoS(x) catalyst.

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