Hierarchical macroporous carbon foam decorated with cobalt oxide nanoparticles exhibit excellent performance for oxygen evolution reaction (OER). The observed electrocatalytic performance is rationalized by the overall 3D macroporous structure and with the firmly integrated CNTs directly grown on the foam. The work is a collaboration with Prof. Mikkola (Umeå, Sweden). The results are published in the journal of Scientific Reports.
Tung Ngoc Pham, Tiva Sharifi, Robin Sandström, William Siljebo, Andrey Shchukarev, Krisztian Kordas, Thomas Wågberg, and Jyri-Pekka Mikkola
Scientific Reports, 7, 6112 (2017) (Download)
Herein we report a 3D heterostructure comprising a hierarchical macroporous carbon foam that incorporates mesoporous carbon nanotubes decorated with cobalt oxide nanoparticles as an unique and highly efficient electrode material for the oxygen evolution reaction (OER) in electrocatalytic water splitting. The best performing electrode material showed high stability after 10 h, at constant potential of 1.7 V vs. RHE (reversible hydrogen electrode) in a 0.1 M KOH solution and high electrocatalytic activity in OER with low overpotential (0.38 V vs RHE at 10 mA cm−2). The excellent electrocatalytic performance of the electrode is rationalized by the overall 3D macroporous structure and with the firmly integrated CNTs directly grown on the foam, resulting in a large specific surface area, good electrical conductivity, as well as an efficient electrolyte transport into the whole electrode matrix concurrent with an ability to quickly dispose oxygen bubbles into the electrolyte. The eminent properties of the three-dimensional structured carbon matrix, which can be synthesized through a simple, scalable and cost effective pyrolysis process show that it has potential to be implemented in large-scale water electrolysis systems.
Here we study the collapsing and spontaneous twisting of a carbon nanotube by in situ transmission electron microscopy (TEM). This work was developed in close collaboration with the research group of Prof. Zettl from the University of California, Berkeley.
Hamid Reza Barzegar, Aiming Yan, Sinisa Coh, Eduardo Gracia-Espino, Claudia Ojeda-Aristizabal, Gabriel Dunn, Marvin L. Cohen, Steven G. Louie, Thomas Wågberg, and Alex Zettl. Nano Res. (2017). doi:10.1007/s12274-016-1380-7
We study the collapsing and subsequent spontaneous twisting of a carbon nanotube by in situ transmission electron microscopy (TEM). A custom-sized nanotube is first created in the microscope by selectively extracting shells from a parent multi-walled tube. The few-walled, large-diameter daughter nanotube is driven to collapse via mechanical stimulation, after which the ribbon-like collapsed tube spontaneously twists along its long axis. In situ diffraction experiments fully characterize the uncollapsed and collapsed tubes. The experimental observations and associated theoretical analysis indicate that the origin of the twisting is compressive strain.
This time we show that collapsed carbon nanotubes can be easily and reliable cycled between their inflated and collapsed states by electrically charging the nanotubes forming nanoballoon actuators. The work has been developed in close collaboration with the research group of Prof. Zettl from the University of California, Berkeley. The results have been published in the journal of Nano Letters.
Hamid Reza Barzegar, Aiming Yan, Sinisa Coh, Eduardo Gracia-Espino, Gabriel Dunn, Thomas Wågberg, Steven G. Louie, Marvin L. Cohen, and Alex Zettl.
Nano Lett., DOI: 10.1021/acs.nanolett.6b02394
We demonstrate an inflatable nanoballoon actuator based on geometrical transitions between the inflated (cylindrical) and collapsed (flattened) forms of a carbon nanotube. In situ transmission electron microscopy experiments employing a nanoelectromechanical manipulator show that a collapsed carbon nanotube can be reinflated by electrically charging the nanotube, thus realizing an electrostatically driven nanoballoon actuator. We find that the tube actuator can be reliably cycled with only modest control voltages (few volts) with no apparent wear or fatigue. A complementary theoretical analysis identifies critical parameters for nanotube nanoballoon actuation.
Toward a Low-Cost Artificial Leaf: Driving Carbon-Based and Bifunctional Catalyst Electrodes with Solution-Processed Perovskite Photovoltaics
This time we report an artificial-leaf device where NiCo2O4 nanorods are used as bifunctional electrode that it can operate as both anode and cathode in the same alkaline solution. By driving two such identical electrodes with a perovskite photovoltaic assembly, a wired artificial-leaf device is obtained that features a Faradaic H2 evolution efficiency of 100%, and a solar-to-hydrogen conversion efficiency of 6.2%. This work was carried out in close collaboration with the research groups of Prof. Edman and Prof. Messinger. The article is published in the journal of Advanced Energy Materials as open access.
Molecular hydrogen can be generated renewably by water splitting with an “artificial-leaf device”, which essentially comprises two electrocatalyst electrodes immersed in water and powered by photovoltaics. Ideally, this device should operate efficiently and be fabricated with cost-efficient means using earth-abundant materials. Here, a lightweight electrocatalyst electrode, comprising large surface-area NiCo2O4 nanorods that are firmly anchored onto a carbon–paper current collector via a dense network of nitrogen-doped carbon nanotubes is presented. This electrocatalyst electrode is bifunctional in that it can efficiently operate as both anode and cathode in the same alkaline solution, as quantified by a delivered current density of 10 mA cm−2 at an overpotential of 400 mV for each of the oxygen and hydrogen evolution reactions. By driving two such identical electrodes with a solution-processed thin-film perovskite photovoltaic assembly, a wired artificial-leaf device is obtained that features a Faradaic H2 evolution efficiency of 100%, and a solar-to-hydrogen conversion efficiency of 6.2%. A detailed cost analysis is presented, which implies that the material-payback time of this device is of the order of 100 days.
Nano for Energy group
Comprehensive Study of an Earth-Abundant Bifunctional 3D Electrode for Efficient Water Electrolysis in Alkaline Medium.
ACS Appl. Mater. Interfaces, 2015, 7, 28148
C60/Collapsed Carbon Nanotube Hybrids - A Variant of Peapods.
Nano Lett., 2015, 15 (2), pp 829–834
Fabrication of One-Dimensional Zigzag [6,6]-Phenyl-C61-Butyric Acid Methyl Ester Nanoribbons from Two-Dimensional Nanosheets.
ACS Nano, 2015, 9, 10516
Hierarchical self-assembled structures based on nitrogen-doped carbon nanotubes as advanced negative electrodes for Li-ion batteries and 3D microbatteries.
J. P. Sources, 2015, 279, 581
.Self-Assembly Synthesis of Decorated Nitrogen-Doped Carbon Nanotubes with ZnO Nanoparticles: Anchoring Mechanism and the Effects of Sulfur.
J. Phys. Chem. C, 120, 27849 (2016)
Sn/Be Sequentially co-doped Hematite Photoanodes for Enhanced Photoelectrochemical Water Oxidation: Effect of Be2+ as co-dopant.
Sci Rep. 2016; 6: 23183.
Atomistic understanding of the origin of high oxygen reduction electrocatalytic activity of cuboctahedral Pt3Co–Pt core–shell nanoparticles.
Catal. Sci. Technol., 2016, 6, 1393-1401
Photocatalytic reduction of CO2 with H2O over modified TiO2 nanofibers: Understanding the reduction pathway.
Nano Res. (2016) 9: 1956.