A Comprehensive Study of an earth-abundant bifunctional 3D electrode for efficient water electrolysis in alkaline medium
We produced an efficient electrocatalyst for both water splitting half reactions in the same medium, where the catalyst compromise Co3O4 nanospheres attached on the surface of nitrogen-doped carbon nanotubes, which in turn are directly grown on conductive carbon paper. The firm and well-established interfaces along the electrode play a crucial role on enhanced stability and electrochemical activity observed for both oxygen evolution reaction and hydrogen reduction reaction. The manuscript has been published in the ACS Applied Materials and Interfaces.
We report efficient electrolysis of both water splitting half reactions in the same medium, by a bifunctional 3D electrode comprising Co3O4 nanospheres nucleated on the surface of nitrogen-doped carbon nanotubes (NCNTs) which in turn are grown on conductive carbon paper (CP). The resulting electrode exhibits high stability and large electrochemical activity for both oxygen and hydrogen evolution reactions (OER and HER). We obtain a current density of 10 mA/cm2 in 0.1 M KOH solution at overpotentials of only 0.47 V and 0.38 V for OER and HER respectively. Additionally, the experimental observations are understood and supported by analyzing the Co3O4:NCNT and NCNT:CP interfaces by ab initio calculations. Both the experimental and the theoretical studies indicate that firm and well-established interfaces along the electrode play a crucial role on the stability and electrochemical activity for both OER and HER.
Atomistic Understanding on the Origin of High Oxygen Reduction Electrocatalytic Activity of Cuboctahedral Pt3Co-Pt Core-Shell Nanoparticles
This time, we report the synthesis of truncated cuboctahedral Pt3Co-Pt core-shell nanoparticles. These nanoparticles are composed of a complete Pt monolayer skin, followed by layers with a ~78 At% of Pt, in a Pt3Co configuration, and finally a Co rich core with just 64 At% of Pt. This specific configuration exhibit an electrocatalytic activity ~6 times higher than commercial 30%-Pt/Vulcan. This work has been published in the Journal of Catalysis Science & Technology, and can be downloaded here.
Guangzhi Hu, Eduardo Gracia-Espino, Robin Sandström, Tiva Sharifi, Shaodong Cheng, Hangjia Shen, Chuanyi Wang, Shaojun Guo, Guang Yang, Thomas Wågberg.
Catal. Sci.Technol., 2015, DOI: 10.1039/C5CY01128K
PtM-based core-shell nanoparticles are a new class of active and stable nanocatalysts to promote oxygen reduction reaction (ORR), however, the understanding at atomistic level of their high electrocatalytic performance for ORR is still a great challenge. Herein, we report a synthesis of highly ordered, and homogeneous truncated cuboctahedral Pt3Co-Pt core-shell nanoparticles (cs-Pt3Co). By combining atomic resolution electron microscopy, X-ray photoelectron spectroscopy, extensive first-principles calculations, and many other characterization techniques, we conclude that the cs-Pt3Co nanoparticles are composed of a complete or nearly complete Pt monolayer skin, followed by a secondary shell containing 5-6 layers with a ~78 At% of Pt, in a Pt3Co configuration, and finally a Co rich core with 64 At% of Pt. Only this particular structure is consistent with the very high electrocatalytic activity of cs-Pt3Co nanoparticles for ORR, which is about 6 times higher than commercial 30%-Pt/Vulcan, and 5 times more active than non-faceted (spherical) alloy Pt3Co nanoparticles. Our study gives an important insight into the atomistic design and understanding of advanced bimetallic nanoparticles for ORR catalysis and other important industrial catalytic applications.
Small palladium islands embedded in palladium–tungsten bimetallic nanoparticles form catalytic hotspots for oxygen reduction
Our most recent article has been published in the journal of Nature Communications, and here, we report a unique novel Pd-W alloy with a Pd content of only 11 At%, which has a similar efficiency as a pure platinum catalyst. This excellent efficiency is explained by the unique morphology of the Pd-W nanoparticles. By advanced experimental and theoretical investigations, we show that the alloy is composed of metallic Pd-islands embedded in a W matrix. The size of the islands are about 1 nm in diameter and are composed of 10-20 atoms that are segregated to the surface. The unique formation of the material is based on the synthesis method, which is performed in an ordinary kitchen micro-wave oven. This study has been conducted in “The artificial leaf” project which is funded by Knut and Alice Wallenberg foundation to physicist, chemists, and plant science researchers at Umeå University.
Guangzhi Hu, Florian Nitze, Eduardo Gracia-Espino, Jingyuan Ma, Hamid Reza Barzegar, Tiva Sharifi, Xueen Jia, Andrey Shchukarev, Lu Lu, Chuansheng Ma, Guang Yang, and Thomas Wågberg
The sluggish kinetics of the oxygen reduction reaction at the cathode side of proton exchange membrane fuel cells is one major technical challenge for realizing sustainable solutions for the transportation sector. Finding efficient yet cheap electrocatalysts to speed up this reaction therefore motivates researchers all over the world.
Here we demonstrate an efficient synthesis of palladium–tungsten bimetallic nanoparticles supported on ordered mesoporous carbon. Despite a very low percentage of noble metal (palladium:tungsten=1:8), the hybrid catalyst material exhibits a performance equal to commercial 60% platinum/Vulcan for the oxygen reduction process. The high catalytic efficiency is explained by the formation of small palladium islands embedded at the surface of the palladium–tungsten bimetallic nanoparticles, generating catalytic hotspots. The palladium islands are ~1 nm in diameter, and contain 10–20 palladium atoms that are segregated at the surface. Our results may provide insight into the formation, stabilization and performance of bimetallic nanoparticles for catalytic reactions.
Palladium Nanocrystals Supported on Photo-transformed C60 Nanorods: Effect of Crystal Morphology and Electron Mobility on the Electrocatalytic Activity Towards Ethanol Oxidation.
This article has been recently published in the journal Carbon, and here, we report the synthesis C60 nanorods (NRs) and its subsequent decoration with palladium nanoparticles. We modified the NR surface via in situ photochemical transformation in the liquid state, in order to obtain highly stable NRs that retain their crystalline structure during the decoration process. We also show that the photo-transformed C60 NRs exhibit highly advantageous properties for ethanol oxidation based on both a better crystallinity and a higher bulk conductivity.
Hamid Reza Barzegar, Guangzhi Hu, Christian Larsen, Xueen Jia, Ludvig Edman, and Thomas Wågberg
Our method thus opens up for the synthesis of highly crystalline nanocomposite hybrids comprising Pd nanoparticles and C60 NRs. Bys measuring the electron mobility of different C60 NRs, we relate both the effect of electron mobility and crystallinity to the final electrocatalytic performance of the synthesized hybrid structures. We show that the photo-transformed C60 NRs exhibit highly advantageous properties for ethanol oxidation based on both a better crystallinity and a higher bulk conductivity. These findings give important information in the search for efficient catalyst support.
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.