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Yang G, Komini Babu S, Liyanage WPR, Martinez U, Routkevitch D, Mukundan R, Borup RL, Cullen DA, Spendelow JS. Coaxial Nanowire Electrodes Enable Exceptional Fuel Cell Durability. Adv Mater 2023; 35:e2301264. [PMID: 37337428 DOI: 10.1002/adma.202301264] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2023] [Revised: 06/08/2023] [Indexed: 06/21/2023]
Abstract
Polymer-electrolyte-membrane fuel cells (PEMFCs) hold great promise for applications in clean energy conversion, but cost and durability continue to limit commercialization. This work presents a new class of catalyst/electrode architecture that does not rely on Pt particles or carbon supports, eliminating the primary degradation mechanisms in conventional electrodes, and thereby enabling transformative durability improvements. The coaxial nanowire electrode (CANE) architecture consists of an array of vertically aligned nanowires, each comprising an ionomer core encapsulated by a nanoscale Pt film. This unique design eliminates the triple-phase boundary and replaces it with two double-phase boundaries, increasing Pt utilization. It also eliminates the need for carbon support and ionomer binder, enabling improved durability and faster mass transport. Fuel cell membrane electrode assemblies based on CANEs demonstrate extraordinary durability in accelerated stress tests (ASTs), with only 2% and 5% loss in performance after 5000 support AST cycles and 30000 catalysts AST cycles, respectively. The high power density and extremely high durability provided by CANEs can enable a paradigm shift from random electrodes based on unstable platinum nanoparticles dispersed on carbon to ordered electrodes based on durable Pt nanofilms, facilitating rapid deployment of fuel cells in transportation and other clean energy applications.
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Affiliation(s)
- Gaoqiang Yang
- MPA-11, Material Physics and Application, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - Siddharth Komini Babu
- MPA-11, Material Physics and Application, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - Wipula P R Liyanage
- MPA-11, Material Physics and Application, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - Ulises Martinez
- MPA-11, Material Physics and Application, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | | | - Rangachary Mukundan
- MPA-11, Material Physics and Application, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - Rodney L Borup
- MPA-11, Material Physics and Application, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - David A Cullen
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Jacob S Spendelow
- MPA-11, Material Physics and Application, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
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2
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Park EJ, Maurya S, Martinez U, Kim YS, Mukundan R. Quaternized poly(arylene ether benzonitrile) membranes for vanadium redox flow batteries. J Memb Sci 2021. [DOI: 10.1016/j.memsci.2020.118565] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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3
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Xie X, He C, Li B, He Y, Cullen DA, Wegener EC, Kropf AJ, Martinez U, Cheng Y, Engelhard MH, Bowden ME, Song M, Lemmon T, Li XS, Nie Z, Liu J, Myers DJ, Zelenay P, Wang G, Wu G, Ramani V, Shao Y. Performance enhancement and degradation mechanism identification of a single-atom Co–N–C catalyst for proton exchange membrane fuel cells. Nat Catal 2020. [DOI: 10.1038/s41929-020-00546-1] [Citation(s) in RCA: 212] [Impact Index Per Article: 53.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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Zhao J, Dumont JH, Martinez U, Macossay J, Artyushkova K, Atanassov P, Gupta G. Graphite Intercalation Compounds Derived by Green Chemistry as Oxygen Reduction Reaction Catalysts. ACS Appl Mater Interfaces 2020; 12:42678-42685. [PMID: 32840099 DOI: 10.1021/acsami.0c09204] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Precious group metal (PGM) catalysts such as Pt supported on carbon supports are expensive catalysts utilized for the oxygen reduction reaction (ORR) due to their unmatched catalytic activity and durability. As an alternative, PGM-free ORR electrocatalysts that offer respectable catalytic activity are being pursued. Most of the notable PGM-free catalysts are obtained either from a bottom-up approach synthesis utilizing nitrogen-rich polymers as building blocks, or from a top down approach, where nitrogen and metal moieties are incorporated to carbonaceous matrixes. The systematic understanding of the origin of catalytic activity for either case is speculative and currently employed synthesis techniques typically generate large amounts of hazardous waste such as acids, oxidizing agents, and solvents. Herein, for the first time, we investigate the catalytic activity of graphite-based materials obtained via intercalation strategies that minimally perturb the graphitic backbone. Our outlined approaches demonstrate initial efforts to not only elucidate the role of each element but also significantly reduce the use of hazardous chemicals, which remains a pressing challenge. Graphite intercalation compounds (GIC) were obtained using fewer steps and solvent-free processes. X-ray diffraction and Raman results confirm the successful intercalation of FeCl3 between graphite layers. Electrochemical data shows that the ORR performance of FeCl3-intercalated GIC displays slight improvement where the onset potential reaches 0.77 V vs RHE in alkaline environments. However, expansion of the graphite and solvent-free incorporation of iron and nitrogen moieties resulted in a significant increase in ORR activity with onset potential to 0.89 V vs RHE, a maximum half-wave of 0.72 V vs RHE, and a limiting current of about 2.5 mA cm-2. We anticipate that the use of near solvent-free processes that result in a high yield of catalysts along with the fundamental insight into the origin of electrochemical activity will tremendously impact the methodologies for developing next-generation ORR catalysts.
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Affiliation(s)
- Jianchao Zhao
- Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
- Chemical Engineering Department, University of Louisville, Louisville, Kentucky 40292, United States
| | - Joseph H Dumont
- Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Ulises Martinez
- Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Javier Macossay
- Chemistry Department, University of Texas Rio Grande Valley, Edinburg, Texas 78539, United States
| | - Kateryna Artyushkova
- Chemical Engineering Department, University of New Mexico, Albuquerque, New Mexico 87131, United States
| | - Plamen Atanassov
- Chemical & Biomolecular Engineering and National Fuel Cell Research Center, University of California, Irvine, California 92697, United States
| | - Gautam Gupta
- Chemical Engineering Department, University of Louisville, Louisville, Kentucky 40292, United States
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5
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Joyner J, Oliveira EF, Yamaguchi H, Kato K, Vinod S, Galvao DS, Salpekar D, Roy S, Martinez U, Tiwary CS, Ozden S, Ajayan PM. Graphene Supported MoS 2 Structures with High Defect Density for an Efficient HER Electrocatalysts. ACS Appl Mater Interfaces 2020; 12:12629-12638. [PMID: 32045208 DOI: 10.1021/acsami.9b17713] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
The development of novel efficient and robust electrocatalysts with sufficient active sites is one of the key parameters for hydrogen evolution reactions (HER) catalysis, which plays a key role in hydrogen production for clean energy harvesting. Recently, two-dimensional (2D) materials, especially those based upon transition metal dichalcogenides such as molybdenum disulfide (MoS2), have gained attention for the catalysis of hydrogen production because of their exceptional properties. Innovative strategies have been developed to engineer these material systems for improvements in their catalytic activity. Toward this aim, the facile growth of MoS2 clusters by sulfurization of molybdenum dioxide (MoO2) particles supported on reduced graphene oxide (rGO) foams using the chemical vapor deposition (CVD) method is reported. This approach created various morphologies of MoS2 with large edges and defect densities on the basal plane of rGO supported MoS2 structures, which are considered as active sites for HER catalysis. In addition, MoS2 nanostructures on the surface of the porous rGO network show robust physical interactions, such as van der Waals and π-π interactions between MoS2 and rGO. These features result in an improved process to yield a suitable HER catalyst. In order to gain a better understanding of the improvement of this MoS2-based HER catalyst, fully atomistic molecular dynamics (MD) simulations of different defect geometries were also performed.
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Affiliation(s)
- Jarin Joyner
- Department of Material Science and NanoEngineering, Rice University, Houston, Texas 77005, United States
- Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
- Department of Chemistry, Rice University, Houston, Texas 77005, United States
| | - Eliezer F Oliveira
- Department of Material Science and NanoEngineering, Rice University, Houston, Texas 77005, United States
- Applied Physics Department, State University of Campinas (UNICAMP), Campinas, Sao Paolo 13083-970, Brazil
- Center for Computational Engineering & Sciences (CCES), State University of Campinas-UNICAMP, Campinas, Sao Paolo 13083-970, Brazil
| | - Hisato Yamaguchi
- Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Keiko Kato
- Department of Material Science and NanoEngineering, Rice University, Houston, Texas 77005, United States
| | - Soumya Vinod
- Department of Material Science and NanoEngineering, Rice University, Houston, Texas 77005, United States
| | - Douglas S Galvao
- Applied Physics Department, State University of Campinas (UNICAMP), Campinas, Sao Paolo 13083-970, Brazil
- Center for Computational Engineering & Sciences (CCES), State University of Campinas-UNICAMP, Campinas, Sao Paolo 13083-970, Brazil
| | - Devashish Salpekar
- Department of Material Science and NanoEngineering, Rice University, Houston, Texas 77005, United States
| | - Soumyabrata Roy
- Department of Material Science and NanoEngineering, Rice University, Houston, Texas 77005, United States
| | - Ulises Martinez
- Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Chandra S Tiwary
- Department of Material Science and NanoEngineering, Rice University, Houston, Texas 77005, United States
- Metallurgical and Materials Engineering, Indian Institute of Technology Kharagpur, Kharagpur 382355, India
| | - Sehmus Ozden
- Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
- Princeton Center for Complex Materials, Princeton University, Princeton, New Jersey 08540, United States
- Princeton Institute for the Science and Technology of Materials, Princeton University, Princeton, New Jersey 08540, United States
- Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08540, United States
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08540, United States
| | - Pulickel M Ajayan
- Department of Material Science and NanoEngineering, Rice University, Houston, Texas 77005, United States
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Sobradillo B, Boyra G, Martinez U, Carrera P, Peña M, Irigoien X. Target Strength and swimbladder morphology of Mueller's pearlside (Maurolicus muelleri). Sci Rep 2019; 9:17311. [PMID: 31754163 PMCID: PMC6872731 DOI: 10.1038/s41598-019-53819-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2019] [Accepted: 11/04/2019] [Indexed: 11/20/2022] Open
Abstract
In the last few years, there has been increasing interest in the commercial exploitation of mesopelagic fish and a trawl-acoustic methodology has been recommended to make estimates of abundance of these resources. This study provides relevant information on the scattering properties of a key mesopelagic fish species in the Bay of Biscay, Mueller's pearlside (Maurolicus muelleri), necessary to convert the acoustic density into numerical abundance. The target strength (TS) of pearlside was estimated for the first time at five frequencies commonly used in acoustic surveys. A high-density filter was applied to reduce the bias derived from overlapping echoes erroneously assigned to single targets. Its relationship with fish length (b20) was also determined (-65.9 ± 2, -69.2 ± 3, -69.2 ± 2, -69.5 ± 2.5 and -71.5 ± 2.5 dB at 18, 38, 70, 120 and 200 kHz, respectively). Biomass estimates of pearlside in the Bay of Biscay during the four years of study (2014-2017) are given using the 38 kHz frequency. Morphological measurements of the swimbladder were obtained from soft X-ray images and used in the backscattering simulation of a gas-filled ellipsoid. Pearlside is a physoclist species, which means that they can compensate the swimbadder volume against pressure changes. However, the best fit between the model and the experimental data showed that they lose that capacity during the trawling process, when the swimbladder volume is affected by Boyle's law.
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Affiliation(s)
- B Sobradillo
- Azti - Marine Research, Herrera kaia, Portualdea z/g - 20110, Pasaia, (Gipuzkoa), Spain.
| | - G Boyra
- Azti - Marine Research, Herrera kaia, Portualdea z/g - 20110, Pasaia, (Gipuzkoa), Spain
| | - U Martinez
- Azti - Marine Research, Herrera kaia, Portualdea z/g - 20110, Pasaia, (Gipuzkoa), Spain
| | - P Carrera
- Instituto Español de Oceanografía, Vigo, Spain
| | - M Peña
- Instituto Español de Oceanografía, Centro Oceanográfico de Baleares, Palma de Mallorca, Spain
| | - X Irigoien
- Azti - Marine Research, Herrera kaia, Portualdea z/g - 20110, Pasaia, (Gipuzkoa), Spain
- IKERBASQUE, Basque Foundation for Science, Bilbao, Spain
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7
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Martinez U, Komini Babu S, Holby EF, Chung HT, Yin X, Zelenay P. Progress in the Development of Fe-Based PGM-Free Electrocatalysts for the Oxygen Reduction Reaction. Adv Mater 2019; 31:e1806545. [PMID: 30790368 DOI: 10.1002/adma.201806545] [Citation(s) in RCA: 135] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2018] [Revised: 11/18/2018] [Indexed: 06/09/2023]
Abstract
Development of alternative energy sources is crucial to tackle challenges encountered by the growing global energy demand. Hydrogen fuel, a promising way to store energy produced from renewable power sources, can be converted into electrical energy at high efficiency via direct electrochemical conversion in fuel cells, releasing water as the sole byproduct. One important drawback to current fuel-cell technology is the high content of platinum-group-metal (PGM) electrocatalysts required to perform the sluggish oxygen reduction reaction (ORR). Addressing this challenge, remarkable progress has been made in the development of low-cost PGM-free electrocatalysts synthesized from inexpensive, earth-abundant, and easily sourced materials such as iron, nitrogen, and carbon (Fe-N-C). PGM-free Fe-N-C electrocatalysts now exhibit ORR activities approaching that of PGM electrocatalysts but at a fraction of the cost, promising to significantly reduce overall fuel-cell technology costs. Herein, recent developments in PGM-free electrocatalysis, demonstrating increased fuel-cell performance, as well as efforts aimed at understanding the key limiting factor, i.e., the nature of the PGM-free active site, are summarized. Further improvements will be accomplished through the controlled and/or rationally designed synthesis of materials with higher active-site densities, while at the same time establishing methods to mitigate catalyst degradation.
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Affiliation(s)
- Ulises Martinez
- Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - Siddharth Komini Babu
- Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - Edward F Holby
- Sigma Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - Hoon T Chung
- Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - Xi Yin
- Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - Piotr Zelenay
- Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
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Ozden S, Bawari S, Vinod S, Martinez U, Susarla S, Narvaez C, Joyner J, Tiwary CS, Narayanan TN, Ajayan PM. Interface and defect engineering of hybrid nanostructures toward an efficient HER catalyst. Nanoscale 2019; 11:12489-12496. [PMID: 31225850 DOI: 10.1039/c9nr01321k] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The hydrogen evolution reaction (HER) plays a key role in hydrogen production for clean energy harvesting. Designing novel efficient and robust electrocatalysts with sufficient active sites and excellent conductivity is one of the key parameters for hydrogen production using water splitting devices. Recently, low-dimensional carbon materials have gained attention as metal-free catalysts for hydrogen production. Such nanostructures need to be engineered to improve their catalytic activity. Here, we designed and synthesized a B and N doped carbon nanostructure (CNS)-hBN heterostructure as an improved HER catalyst. The hBN layers on CNS could provide exposed defects and edges that act as active sites for proton adsorption and reduction. The composition, structure and chemical properties of the B and N doped CNS-hBN heterostructure were tuned to obtain excellent HER activity. Detailed morphological, structural and electrochemical characterization demonstrated that the synergistic effect rising from the interaction between B and N doped CNS and hBN structures contributes to enhance the electrocatalytic performances. To get more insight into the role of defects and doping, we performed density functional theory (DFT) calculations on the CNS-hBN heterostructure.
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Affiliation(s)
- Sehmus Ozden
- Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, NM, USA.
| | - Sumit Bawari
- Tata Institute of Fundamental Research-Hyderabad, Sy. No. 36/P, Gopanapally Village, Serilingampally Mandal, Hyderabad-500 107, India
| | - Soumya Vinod
- Department of Material Science and NanoEngineering, Rice University, Houston, Texas, 77005 USA
| | - Ulises Martinez
- Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, NM, USA.
| | - Sandhya Susarla
- Department of Material Science and NanoEngineering, Rice University, Houston, Texas, 77005 USA
| | - Claudia Narvaez
- Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, NM, USA.
| | - Jarin Joyner
- Department of Material Science and NanoEngineering, Rice University, Houston, Texas, 77005 USA
| | - Chandra Sekhar Tiwary
- Metallurgical and materials Engineering, Indian Institute of Technology Kharagpur, Kharagpur-721302, India
| | - Tharangattu N Narayanan
- Tata Institute of Fundamental Research-Hyderabad, Sy. No. 36/P, Gopanapally Village, Serilingampally Mandal, Hyderabad-500 107, India
| | - Pulickel M Ajayan
- Department of Material Science and NanoEngineering, Rice University, Houston, Texas, 77005 USA
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9
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Zhang J, Wu J, Guo H, Chen W, Yuan J, Martinez U, Gupta G, Mohite A, Ajayan PM, Lou J. Unveiling Active Sites for the Hydrogen Evolution Reaction on Monolayer MoS 2. Adv Mater 2017; 29:1701955. [PMID: 28940336 DOI: 10.1002/adma.201701955] [Citation(s) in RCA: 120] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2017] [Revised: 08/07/2017] [Indexed: 05/22/2023]
Abstract
Here, the hydrogen evolution reaction (HER) activities at the edge and basal-plane sites of monolayer molybdenum disulfide (MoS2 ) synthesized by chemical vapor deposition (CVD) are studied using a local probe method enabled by selected-area lithography. Reaction windows are opened by e-beam lithography at sites of interest on poly(methyl methacrylate) (PMMA)-covered monolayer MoS2 triangles. The HER properties of MoS2 edge sites are obtained by subtraction of the activity of the basal-plane sites from results containing both basal-plane and edge sites. The catalytic performances in terms of turnover frequencies (TOFs) are calculated based on the estimated number of active sites on the selected areas. The TOFs follow a descending order of 3.8 ± 1.6, 1.6 ± 1.2, 0.008 ± 0.002, and 1.9 ± 0.8 × 10-4 s-1 , found for 1T'-, 2H-MoS2 edges, and 1T'-, 2H-MoS2 basal planes, respectively. Edge sites of both 2H- and 1T'-MoS2 are proved to have comparable activities to platinum (≈1-10 s-1 ). When fitted into the HER volcano plot, the MoS2 active sites follow a trend distinct from conventional metals, implying a possible difference in the reaction mechanism between transition-metal dichalcogenides (TMDs) and metal catalysts.
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Affiliation(s)
- Jing Zhang
- Department of Materials Science and NanoEngineering, Rice University, Houston, TX, 77005, USA
| | - Jingjie Wu
- Department of Materials Science and NanoEngineering, Rice University, Houston, TX, 77005, USA
| | - Hua Guo
- Department of Materials Science and NanoEngineering, Rice University, Houston, TX, 77005, USA
| | - Weibing Chen
- Department of Materials Science and NanoEngineering, Rice University, Houston, TX, 77005, USA
| | - Jiangtan Yuan
- Department of Materials Science and NanoEngineering, Rice University, Houston, TX, 77005, USA
| | - Ulises Martinez
- MPA-11, Los Alamos National Laboratory, Los Alamos, NM, 87544, USA
| | - Gautam Gupta
- MPA-11, Los Alamos National Laboratory, Los Alamos, NM, 87544, USA
| | - Aditya Mohite
- MPA-11, Los Alamos National Laboratory, Los Alamos, NM, 87544, USA
| | - Pulickel M Ajayan
- Department of Materials Science and NanoEngineering, Rice University, Houston, TX, 77005, USA
| | - Jun Lou
- Department of Materials Science and NanoEngineering, Rice University, Houston, TX, 77005, USA
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10
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Abstract
Rotating disk electrode voltammograms and infrared reflection absorption spectra indicate that the hydrogen oxidation reaction of platinum in 0.1 M tetramethylammonium hydroxide solution is adversely impacted by time-dependent and potential-driven cation-hydroxide-water coadsorption. Impedance analysis suggests that the hydrogen oxidation reaction inhibition is mainly caused by the hydrogen diffusion barrier of the coadsorbed trilayer rather than intuitive catalyst site blocking by the adsorbed cation species. These results give useful insights on how to design ionomeric binders for advanced alkaline membrane fuel cells.
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Affiliation(s)
- Hoon Taek Chung
- MPA-11: Materials Synthesis and Integrated Devices, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States
| | - Ulises Martinez
- MPA-11: Materials Synthesis and Integrated Devices, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States
| | - Ivana Matanovic
- Department of Chemical and Biological Engineering, Center for Micro-Engineered Materials (CMEM), The University of New Mexico , Albuquerque, New Mexico 87231, United States
- T-1: Physics and Chemistry of Materials, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States
| | - Yu Seung Kim
- MPA-11: Materials Synthesis and Integrated Devices, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States
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11
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Dumont JH, Martinez U, Chung HT, Zelenay P. Inside Back Cover: Ternary PtRuPd/C Catalyst for High-Performance, Low-Temperature Direct Dimethyl Ether Fuel Cells (ChemElectroChem 10/2016). ChemElectroChem 2016. [DOI: 10.1002/celc.201600569] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Joseph H. Dumont
- Materials Physics and Applications Division; Los Alamos National Laboratory; Los Alamos NM 87545 USA
| | - Ulises Martinez
- Materials Physics and Applications Division; Los Alamos National Laboratory; Los Alamos NM 87545 USA
| | - Hoon T. Chung
- Materials Physics and Applications Division; Los Alamos National Laboratory; Los Alamos NM 87545 USA
| | - Piotr Zelenay
- Materials Physics and Applications Division; Los Alamos National Laboratory; Los Alamos NM 87545 USA
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12
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Dumont JH, Martinez U, Chung HT, Zelenay P. Ternary PtRuPd/C Catalyst for High-Performance, Low-Temperature Direct Dimethyl Ether Fuel Cells. ChemElectroChem 2016. [DOI: 10.1002/celc.201600336] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Joseph H. Dumont
- Materials Physics and Applications Division; Los Alamos National Laboratory; Los Alamos NM 87545 USA
| | - Ulises Martinez
- Materials Physics and Applications Division; Los Alamos National Laboratory; Los Alamos NM 87545 USA
| | - Hoon T. Chung
- Materials Physics and Applications Division; Los Alamos National Laboratory; Los Alamos NM 87545 USA
| | - Piotr Zelenay
- Materials Physics and Applications Division; Los Alamos National Laboratory; Los Alamos NM 87545 USA
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13
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Cummins DR, Martinez U, Sherehiy A, Kappera R, Martinez-Garcia A, Schulze RK, Jasinski J, Zhang J, Gupta RK, Lou J, Chhowalla M, Sumanasekera G, Mohite AD, Sunkara MK, Gupta G. Efficient hydrogen evolution in transition metal dichalcogenides via a simple one-step hydrazine reaction. Nat Commun 2016; 7:11857. [PMID: 27282871 PMCID: PMC4906413 DOI: 10.1038/ncomms11857] [Citation(s) in RCA: 160] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2015] [Accepted: 05/06/2016] [Indexed: 12/24/2022] Open
Abstract
Hydrogen evolution reaction is catalysed efficiently with precious metals, such as platinum; however, transition metal dichalcogenides have recently emerged as a promising class of materials for electrocatalysis, but these materials still have low activity and durability when compared with precious metals. Here we report a simple one-step scalable approach, where MoOx/MoS2 core-shell nanowires and molybdenum disulfide sheets are exposed to dilute aqueous hydrazine at room temperature, which results in marked improvement in electrocatalytic performance. The nanowires exhibit ∼100 mV improvement in overpotential following exposure to dilute hydrazine, while also showing a 10-fold increase in current density and a significant change in Tafel slope. In situ electrical, gate-dependent measurements and spectroscopic investigations reveal that hydrazine acts as an electron dopant in molybdenum disulfide, increasing its conductivity, while also reducing the MoOx core in the core-shell nanowires, which leads to improved electrocatalytic performance. Transition metal dichalcogenides are promising hydrogen evolution catalysts however they can require expensive processing steps to enhance their activity. Here, the authors report a one-step activation step in which room temperature hydrazine treatment results in much enhanced electrocatalytic performance.
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Affiliation(s)
- Dustin R Cummins
- Materials Physics and Applications (MPA-11), Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.,Chemical Engineering and Conn Center for Renewable Energy Research, University of Louisville, Louisville, Kentucky 40292, USA
| | - Ulises Martinez
- Materials Physics and Applications (MPA-11), Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - Andriy Sherehiy
- Chemical Engineering and Conn Center for Renewable Energy Research, University of Louisville, Louisville, Kentucky 40292, USA
| | - Rajesh Kappera
- Materials Physics and Applications (MPA-11), Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.,Materials Science and Engineering, Rutgers University, Piscataway, New Jersey 08854, USA
| | - Alejandro Martinez-Garcia
- Chemical Engineering and Conn Center for Renewable Energy Research, University of Louisville, Louisville, Kentucky 40292, USA
| | - Roland K Schulze
- Materials Science and Technology (MST-6), Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - Jacek Jasinski
- Chemical Engineering and Conn Center for Renewable Energy Research, University of Louisville, Louisville, Kentucky 40292, USA
| | - Jing Zhang
- Materials Science and NanoEngineering, Rice University, Houston, Texas 77005, USA
| | - Ram K Gupta
- Chemistry, Pittsburg State University, Pittsburg, Kansas 66762, USA
| | - Jun Lou
- Materials Science and NanoEngineering, Rice University, Houston, Texas 77005, USA
| | - Manish Chhowalla
- Materials Science and Engineering, Rutgers University, Piscataway, New Jersey 08854, USA
| | - Gamini Sumanasekera
- Chemical Engineering and Conn Center for Renewable Energy Research, University of Louisville, Louisville, Kentucky 40292, USA
| | - Aditya D Mohite
- Materials Physics and Applications (MPA-11), Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - Mahendra K Sunkara
- Chemical Engineering and Conn Center for Renewable Energy Research, University of Louisville, Louisville, Kentucky 40292, USA
| | - Gautam Gupta
- Materials Physics and Applications (MPA-11), Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
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14
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Martinez U, Dumont JH, Holby EF, Artyushkova K, Purdy GM, Singh A, Mack NH, Atanassov P, Cullen DA, More KL, Chhowalla M, Zelenay P, Dattelbaum AM, Mohite AD, Gupta G. Critical role of intercalated water for electrocatalytically active nitrogen-doped graphitic systems. Sci Adv 2016; 2:e1501178. [PMID: 27034981 PMCID: PMC4803488 DOI: 10.1126/sciadv.1501178] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2015] [Accepted: 01/14/2016] [Indexed: 05/30/2023]
Abstract
Graphitic materials are essential in energy conversion and storage because of their excellent chemical and electrical properties. The strategy for obtaining functional graphitic materials involves graphite oxidation and subsequent dissolution in aqueous media, forming graphene-oxide nanosheets (GNs). Restacked GNs contain substantial intercalated water that can react with heteroatom dopants or the graphene lattice during reduction. We demonstrate that removal of intercalated water using simple solvent treatments causes significant structural reorganization, substantially affecting the oxygen reduction reaction (ORR) activity and stability of nitrogen-doped graphitic systems. Amid contrasting reports describing the ORR activity of GN-based catalysts in alkaline electrolytes, we demonstrate superior activity in an acidic electrolyte with an onset potential of ~0.9 V, a half-wave potential (E ½) of 0.71 V, and a selectivity for four-electron reduction of >95%. Further, durability testing showed E ½ retention >95% in N2- and O2-saturated solutions after 2000 cycles, demonstrating the highest ORR activity and stability reported to date for GN-based electrocatalysts in acidic media.
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Affiliation(s)
- Ulises Martinez
- Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
| | - Joseph H. Dumont
- Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
- Department of Chemical and Biological Engineering, University of New Mexico, Albuquerque, NM 87131, USA
| | - Edward F. Holby
- Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
| | - Kateryna Artyushkova
- Department of Chemical and Biological Engineering, University of New Mexico, Albuquerque, NM 87131, USA
| | - Geraldine M. Purdy
- Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
| | - Akhilesh Singh
- Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
| | - Nathan H. Mack
- Chemistry Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
| | - Plamen Atanassov
- Department of Chemical and Biological Engineering, University of New Mexico, Albuquerque, NM 87131, USA
| | - David A. Cullen
- Materials Science and Technology Division, Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Karren L. More
- Materials Science and Technology Division, Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Manish Chhowalla
- Science and Engineering, Rutgers University, 607 Taylor Road, Piscataway, NJ 08854, USA
| | - Piotr Zelenay
- Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
| | - Andrew M. Dattelbaum
- Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
| | - Aditya D. Mohite
- Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
| | - Gautam Gupta
- Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
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15
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Zalineeva A, Serov A, Padilla M, Martinez U, Artyushkova K, Baranton S, Coutanceau C, Atanassov P. Nano-structured Pd-Sn catalysts for alcohol electro-oxidation in alkaline medium. Electrochem commun 2015. [DOI: 10.1016/j.elecom.2015.05.006] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
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16
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Yalcin SE, Galande C, Kappera R, Yamaguchi H, Martinez U, Velizhanin KA, Doorn SK, Dattelbaum AM, Chhowalla M, Ajayan PM, Gupta G, Mohite AD. Direct imaging of charge transport in progressively reduced graphene oxide using electrostatic force microscopy. ACS Nano 2015; 9:2981-2988. [PMID: 25668323 DOI: 10.1021/nn507150q] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Graphene oxide (GO) has emerged as a multifunctional material that can be synthesized in bulk quantities and can be solution processed to form large-area atomic layered photoactive, flexible thin films for optoelectronic devices. This is largely due to the potential ability to tune electrical and optical properties of GO using functional groups. For the successful application of GO, it is key to understand the evolution of its optoelectronic properties as the GO undergoes a phase transition from its insulating and optically active state to the electrically conducting state with progressive reduction. In this paper, we use a combination of electrostatic force microscopy (EFM) and optical spectroscopy to monitor the emergence of the optoelectronic properties of GO with progressive reduction. EFM measurements enable, for the first time, direct visualization of charge propagation along the conducting pathways that emerge on progressively reduced graphene oxide (rGO) and demonstrate that with the increasing degree of reduction, injected charges can rapidly migrate over a distance of several micrometers, irrespective of their polarities. Direct imaging reveals the presence of an insurmountable potential barrier between reduced GO (rGO) and GO, which plays the decisive role in the charge transport. We complement charge imaging with theoretical modeling using quantum chemistry calculations that further demonstrate that the role of barrier in regulating the charge transport. Furthermore, by correlating the EFM measurements with photoluminescence imaging and electrical conductivity studies, we identify a bifunctional state in GO, where the optical properties are preserved along with good electrical conductivity, providing design principles for the development of GO-based, low-cost, thin-film optoelectronic applications.
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Affiliation(s)
- Sibel Ebru Yalcin
- †Center for Integrated Nanotechnologies, Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | | | | | - Hisato Yamaguchi
- ⊥MPA-11 Materials Synthesis and Integrated Devices, Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Ulises Martinez
- ⊥MPA-11 Materials Synthesis and Integrated Devices, Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Kirill A Velizhanin
- ∥T-1 Physics and Chemistry of Materials, Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Stephen K Doorn
- †Center for Integrated Nanotechnologies, Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Andrew M Dattelbaum
- ⊥MPA-11 Materials Synthesis and Integrated Devices, Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | | | | | - Gautam Gupta
- ⊥MPA-11 Materials Synthesis and Integrated Devices, Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Aditya D Mohite
- ⊥MPA-11 Materials Synthesis and Integrated Devices, Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
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17
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Martinez U, Serov A, Padilla M, Atanassov P. Mechanistic insight into oxide-promoted palladium catalysts for the electro-oxidation of ethanol. ChemSusChem 2014; 7:2351-2357. [PMID: 24984856 DOI: 10.1002/cssc.201402062] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2014] [Revised: 04/03/2014] [Indexed: 06/03/2023]
Abstract
Recent advancements in the development of alternatives to proton exchange membrane fuel cells utilizing less-expensive catalysts and renewable liquid fuels, such as alcohols, has been observed for alkaline fuel cell systems. Alcohol fuels present the advantage of not facing the challenge of storage and transportation encountered with hydrogen fuel. Oxidation of alcohols has been improved by the promotion of alloyed or secondary phases. Nevertheless, currently, there is no experimental understanding of the difference between an intrinsic and a synergistic promotion effect in high-pH environments. This report shows evidence of different types of promotion effects on palladium electrocatalysts obtained from the presence of an oxide phase for the oxidation of ethanol. The correlation of mechanistic in situ IR spectroscopic studies with electrochemical voltammetry studies on two similar electrocatalytic systems allow the role of either an alloyed or a secondary phase on the mechanism of oxidation of ethanol to be elucidated. Evidence is presented for the difference between an intrinsic effect obtained from an alloyed system and a synergistic effect produced by the presence of an oxide phase.
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Affiliation(s)
- Ulises Martinez
- Center for Emerging Energy Technologies, The University of New Mexico, 1 University of New Mexico-MSC01 1120, Albuquerque, NM 87131 (USA); Present Address: Materials Physics and Applications, Los Alamos National Laboratory, Los Alamos, NM 87545 (USA)
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18
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Zalineeva A, Serov A, Padilla M, Martinez U, Artyushkova K, Baranton S, Coutanceau C, Atanassov PB. Self-Supported PdxBi Catalysts for the Electrooxidation of Glycerol in Alkaline Media. J Am Chem Soc 2014; 136:3937-45. [DOI: 10.1021/ja412429f] [Citation(s) in RCA: 213] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Anna Zalineeva
- Université
de Poitiers, IC2MP, UMR CNRS 7285, “Catalysis and Non-conventional
Media” group, 4 rue Michel Brunet, 86073 Poitiers Cedex 9, France
| | - Alexey Serov
- Department
of Chemical and Nuclear Engineering and Center for Emerging Energy
Technologies, University of New Mexico, Albuquerque, New Mexico 87131, United States
| | - Monica Padilla
- Department
of Chemical and Nuclear Engineering and Center for Emerging Energy
Technologies, University of New Mexico, Albuquerque, New Mexico 87131, United States
| | - Ulises Martinez
- Department
of Chemical and Nuclear Engineering and Center for Emerging Energy
Technologies, University of New Mexico, Albuquerque, New Mexico 87131, United States
| | - Kateryna Artyushkova
- Department
of Chemical and Nuclear Engineering and Center for Emerging Energy
Technologies, University of New Mexico, Albuquerque, New Mexico 87131, United States
| | - Stève Baranton
- Université
de Poitiers, IC2MP, UMR CNRS 7285, “Catalysis and Non-conventional
Media” group, 4 rue Michel Brunet, 86073 Poitiers Cedex 9, France
| | - Christophe Coutanceau
- Université
de Poitiers, IC2MP, UMR CNRS 7285, “Catalysis and Non-conventional
Media” group, 4 rue Michel Brunet, 86073 Poitiers Cedex 9, France
| | - Plamen B. Atanassov
- Department
of Chemical and Nuclear Engineering and Center for Emerging Energy
Technologies, University of New Mexico, Albuquerque, New Mexico 87131, United States
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19
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Irigoien X, Klevjer TA, Røstad A, Martinez U, Boyra G, Acuña JL, Bode A, Echevarria F, Gonzalez-Gordillo JI, Hernandez-Leon S, Agusti S, Aksnes DL, Duarte CM, Kaartvedt S. Large mesopelagic fishes biomass and trophic efficiency in the open ocean. Nat Commun 2014; 5:3271. [PMID: 24509953 PMCID: PMC3926006 DOI: 10.1038/ncomms4271] [Citation(s) in RCA: 176] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2013] [Accepted: 01/16/2014] [Indexed: 11/09/2022] Open
Abstract
With a current estimate of ~1,000 million tons, mesopelagic fishes likely dominate the world total fishes biomass. However, recent acoustic observations show that mesopelagic fishes biomass could be significantly larger than the current estimate. Here we combine modelling and a sensitivity analysis of the acoustic observations from the Malaspina 2010 Circumnavigation Expedition to show that the previous estimate needs to be revised to at least one order of magnitude higher. We show that there is a close relationship between the open ocean fishes biomass and primary production, and that the energy transfer efficiency from phytoplankton to mesopelagic fishes in the open ocean is higher than what is typically assumed. Our results indicate that the role of mesopelagic fishes in oceanic ecosystems and global ocean biogeochemical cycles needs to be revised as they may be respiring ~10% of the primary production in deep waters.
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Affiliation(s)
- Xabier Irigoien
- King Abdullah University of Science and Technology (KAUST), Red Sea Research Center, Thuwal 23955-6900, Saudi Arabia
| | - T. A. Klevjer
- King Abdullah University of Science and Technology (KAUST), Red Sea Research Center, Thuwal 23955-6900, Saudi Arabia
| | - A. Røstad
- King Abdullah University of Science and Technology (KAUST), Red Sea Research Center, Thuwal 23955-6900, Saudi Arabia
| | - U. Martinez
- AZTI, Arrantza eta Elikaigintzarako Institutu Teknologikoa, Herrera Kaia Portualdea, 20110 Pasaia, Spain
| | - G. Boyra
- AZTI, Arrantza eta Elikaigintzarako Institutu Teknologikoa, Herrera Kaia Portualdea, 20110 Pasaia, Spain
| | - J. L. Acuña
- Departamento de Biología de Organismos y Sistemas, Universidad de Oviedo, Calle Catedrático Rodrigo Uría, Sin Número, 33071 Oviedo, Spain
| | - A. Bode
- Instituto Español de Oceanografía (IEO), Centro Oceanográfico de A Coruña, Apdo 130, E15080 A Coruña, Spain
| | - F. Echevarria
- Departamento de Biología, Facultad de Ciencias del Mar y Ambientales, Universidad de Cádiz, Campus de Excelencia Internacional del Mar (CEI·MAR), E-11510 Puerto Real, Spain
| | - J. I. Gonzalez-Gordillo
- Departamento de Biología, Facultad de Ciencias del Mar y Ambientales, Universidad de Cádiz, Campus de Excelencia Internacional del Mar (CEI·MAR), E-11510 Puerto Real, Spain
| | - S. Hernandez-Leon
- Institute of Oceanography and Global Change, Universidad de Las Palmas de Gran Canaria, Campus Universitario de Tafira, Las Palmas de Gran Canaria, 35017 Canary Islands, Spain
| | - S. Agusti
- The UWA Oceans Institute and School of Plant Biology, University of Western Australia, 35 Stirling Highway, Crawley, Western Australia 6009, Australia
- Department of Global Change Research, IMEDEA (UIB-CSIC), Instituto Mediterráneo de Estudios Avanzados, Esporles 07190, Spain
| | - D. L. Aksnes
- Department of Biology, University of Bergen, Bergen N-5020, Norway
| | - C. M. Duarte
- The UWA Oceans Institute and School of Plant Biology, University of Western Australia, 35 Stirling Highway, Crawley, Western Australia 6009, Australia
- Department of Global Change Research, IMEDEA (UIB-CSIC), Instituto Mediterráneo de Estudios Avanzados, Esporles 07190, Spain
| | - S. Kaartvedt
- King Abdullah University of Science and Technology (KAUST), Red Sea Research Center, Thuwal 23955-6900, Saudi Arabia
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Kristoffersen HH, Hansen JO, Martinez U, Wei YY, Matthiesen J, Streber R, Bechstein R, Lægsgaard E, Besenbacher F, Hammer B, Wendt S. Role of steps in the dissociative adsorption of water on rutile TiO2(110). Phys Rev Lett 2013; 110:146101. [PMID: 25167009 DOI: 10.1103/physrevlett.110.146101] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2012] [Revised: 02/05/2013] [Indexed: 05/20/2023]
Abstract
The water-TiO(2) interaction is of paramount importance for many processes occurring on TiO(2), and the rutile TiO(2)(110)-(1×1) surface has often been considered as a test case. Yet, no consensus has been reached whether the well-studied surface O vacancies on the terraces are the only active sites for water dissociation on rutile TiO(2)(110)-(1 × 1), or whether another channel for the creation of H adatoms exists. Here we use high-resolution scanning tunneling microscopy and density functional theory calculations to tackle this long-standing question. Evidence is presented that a second water dissociation channel exists on the surfaces of vacuum-annealed TiO(2)(110) crystals that is associated with the ⟨111⟩ step edges. This second water dissociation channel can be suppressed by blocking of the ⟨111⟩ step edges using ethanol.
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Affiliation(s)
- H H Kristoffersen
- Interdisciplinary Nanoscience Center (iNANO), Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C, Denmark
| | - J O Hansen
- Interdisciplinary Nanoscience Center (iNANO), Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C, Denmark
| | - U Martinez
- Interdisciplinary Nanoscience Center (iNANO), Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C, Denmark
| | - Y Y Wei
- Interdisciplinary Nanoscience Center (iNANO), Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C, Denmark
| | - J Matthiesen
- Interdisciplinary Nanoscience Center (iNANO), Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C, Denmark
| | - R Streber
- Interdisciplinary Nanoscience Center (iNANO), Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C, Denmark
| | - R Bechstein
- Interdisciplinary Nanoscience Center (iNANO), Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C, Denmark
| | - E Lægsgaard
- Interdisciplinary Nanoscience Center (iNANO), Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C, Denmark
| | - F Besenbacher
- Interdisciplinary Nanoscience Center (iNANO), Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C, Denmark
| | - B Hammer
- Interdisciplinary Nanoscience Center (iNANO), Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C, Denmark
| | - S Wendt
- Interdisciplinary Nanoscience Center (iNANO), Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C, Denmark
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22
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Martinez U, Hansen JØ, Lira E, Kristoffersen HH, Huo P, Bechstein R, Lægsgaard E, Besenbacher F, Hammer B, Wendt S. Reduced step edges on rutile TiO2(110) as competing defects to oxygen vacancies on the terraces and reactive sites for ethanol dissociation. Phys Rev Lett 2012; 109:155501. [PMID: 23102329 DOI: 10.1103/physrevlett.109.155501] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2012] [Indexed: 05/20/2023]
Abstract
The rutile TiO2(110) surface is the most studied surface of titania and considered as a prototype of transition metal oxide surfaces. Reactions on flat TiO2(110)-(1×1) surfaces are well studied, but the processes occurring on the step edges have barely been considered. Based on scanning tunneling microscopy studies, we here present experimental evidence for the existence of O vacancies along the [11¯1](R) step edges (O(S) vac.'s) on rutile TiO(2)(110). Both the distribution of bridging O vacancies on the terraces and temperature-programed reaction experiments of ethanol-covered TiO(2)(110) point to the existence of the O(S) vac.'s. Based on experiments and density functional theory calculations, we show that O(S) vac.'s are reactive sites for ethanol dissociation via O-H bond scission. Implications of these findings are discussed.
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Affiliation(s)
- U Martinez
- Interdisciplinary Nanoscience Center (iNANO), Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C, Denmark
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23
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24
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Martinez U, Asazawa K, Halevi B, Falase A, Kiefer B, Serov A, Padilla M, Olson T, Datye A, Tanaka H, Atanassov P. Aerosol-derived Ni1−xZnx electrocatalysts for direct hydrazine fuel cells. Phys Chem Chem Phys 2012; 14:5512-7. [DOI: 10.1039/c2cp40546f] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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25
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Hansen JO, Huo P, Martinez U, Lira E, Wei YY, Streber R, Laegsgaard E, Hammer B, Wendt S, Besenbacher F. Direct evidence for ethanol dissociation on rutile TiO2(110). Phys Rev Lett 2011; 107:136102. [PMID: 22026875 DOI: 10.1103/physrevlett.107.136102] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2011] [Indexed: 05/31/2023]
Abstract
We have studied the interaction of ethanol with reduced TiO(2)(110)-(1 × 1) by high-resolution scanning tunneling microscopy (STM) measurements and density functional theory calculations. The STM data revealed direct evidence for the coexistence of molecularly and dissociatively adsorbed ethanol species on surface Ti sites. In addition, we found evidence for dissociation of ethanol at bridge-bonded O vacancies. The density functional theory calculations support these findings and rationalize the distinct diffusion behaviors of molecularly and dissociatively adsorbed ethanol species, as revealed in time-lapsed STM images.
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Affiliation(s)
- J O Hansen
- Interdisciplinary Nanoscience Center, Department of Physics and Astronomy, Aarhus University, Denmark
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26
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Jourdi H, Yanagihara T, Martinez U, Bi X, Lynch G, Baudry M. Effects of positive AMPA receptor modulators on calpain-mediated spectrin degradation in cultured hippocampal slices. Neurochem Int 2005; 46:31-40. [PMID: 15567513 DOI: 10.1016/j.neuint.2004.07.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2004] [Revised: 07/06/2004] [Accepted: 07/13/2004] [Indexed: 10/26/2022]
Abstract
Positive modulators of AMPA receptors (AMPAr), also known as ampakines, are allosteric effectors of the receptors and have been extensively studied in past years due to their potential use as treatment for various diseases and ailments of the central nervous system such as mild cognitive impairment, schizophrenia, and Alzheimer's disease. Ampakines have been shown to improve performance on memory tasks in animals and in human subjects, an effect linked to their ability to increase agonist-mediated ion influx through AMPAr, thus leading to enhanced synaptic responses and facilitation of long-term potentiation (LTP) induction at glutamatergic synapses. As LTP is associated with calpain activation and spectrin degradation, we determined the effects of ampakine treatment of cultured hippocampal slices on spectrin degradation. Calpain activation was evaluated by determining the levels of the 145-150kDa degradation products of spectrin. Our data indicated that incubation of hippocampal slices with some, but not all positive modulators of AMPA receptors resulted in enhanced spectrin degradation, an effect that was blocked by a calpain inhibitor. In addition, an antagonist of AMPAr but not of NMDAr blocked ampakine-induced spectrin degradation. These results indicate that prolonged treatment with selected ampakines leads to spectrin degradation mediated by activation of the calcium-dependent protease calpain.
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Affiliation(s)
- Hussam Jourdi
- Neuroscience Program, University of Southern California, Los Angeles, CA 90089-2520, USA
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27
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Martinez T, Cabrera L, Navarrete M, Garcia JJ, Gonzalez P, Ramirez A, Martinez U. Gamma radiation and radon levels in Mexico City dwellings. J Radioanal Nucl Chem 1995. [DOI: 10.1007/bf02039883] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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