Jul 2, 2015

Ultra-small Palladium Nanoparticle Decorated Carbon Nanotubes: Conductivity and Reactivity

Xiuting Li, Dr. Christopher Batchelor-McAuley, Dr. Kristina Tschulik, Prof. Dr. Lidong Shao and Prof. Dr. Richard G. Compton
Article first published online: 10 JUN 2015 | DOI: 10.1002/cphc.201500404
Thumbnail image of graphical abstract
Small but mighty: Individual multiwalled carbon nanotubes decorated with ultra-small palladium nanoparticles are detected by using the nano-impacts method through studying the proton-reduction reaction for the underpotential deposition of hydrogen on palladium nanoparticles. The high conductivity and reactivity of the decorated carbon nanotubes is directly evidenced.

Jul 1, 2015

Highly Active, Nonprecious Metal Perovskite Electrocatalysts for Bifunctional Metal–Air Battery Electrodes

 http://pubs.acs.org/doi/abs/10.1021/jz400595z?source=chemport

 Highly Active, Nonprecious Metal Perovskite Electrocatalysts for Bifunctional Metal–Air Battery Electrodes

Department of Chemical Engineering (1 University Station C0400), Department of Chemistry and Biochemistry (1 University Station A5300), §Center for Electrochemistry, and Texas Materials Institute, The University of Texas at Austin, Austin, Texas 78712, United States
# Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
J. Phys. Chem. Lett., 2013, 4 (8), pp 1254–1259
DOI: 10.1021/jz400595z
Publication Date (Web): March 27, 2013
Copyright © 2013 American Chemical Society
OpenURL YALE UNIV
*E-mail: stevenson@cm.utexas.edu (K.J.S.); kpj@che.utexas.edu (K.P.J.).

Abstract

Abstract Image
Perovskites are of great interest as replacements for precious metals and oxides used in bifunctional air electrodes involving the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Herein, we report the synthesis and activity of a phase-pure nanocrystal perovskite catalyst that is highly active for the OER and ORR. The OER mass activity of LaNiO3, synthesized by the calcination of a rapidly dried nanoparticle dispersion and supported on nitrogen-doped carbon, is demonstrated to be nearly 3-fold that of 6 nm IrO2 and exhibits no hysteresis during oxygen evolution. Moreover, strong OER/ORR bifunctionality is shown by the low total overpotential (1.02 V) between the reactions, on par or better than that of noble metal catalysts such as Pt (1.16 V) and Ir (0.92 V). These results are examined in the context of surface hydroxylation, and a new OER cycle is proposed that unifies theory and the unique surface properties of LaNiO3.

Jun 26, 2015

Ultrafast Transient Absorption Study of the Nature of Interaction between Oppositely Charged Photoexcited CdTe Quantum Dots and Cresyl Violet


Ultrafast Transient Absorption Study of the Nature of Interaction between Oppositely Charged Photoexcited CdTe Quantum Dots and Cresyl Violet by M. Chandra Sekhar and Anunay Samanta via The Journal of Physical Chemistry C: Latest Articles (ACS Publications) http://ift.tt/1J2QAcM http://pubs.acs.org

Jun 23, 2015

Saved: Ligand-Induced Proton Transfer and Low-Barrier Hydrogen Bond Revealed by X-ray Crystallography


Ligand-Induced Proton Transfer and Low-Barrier Hydrogen Bond Revealed by X-ray Crystallography by Derek A. Nichols, Jacqueline C. Hargis, Ruslan Sanishvili, Priyadarshini Jaishankar, Kyle Defrees, Emmanuel W. Smith, Kenneth K. Wang, Fabio Prati, Adam R. Renslo, H. Lee Woodcock and Yu Chen via Journal of the American Chemical Society: Latest Articles (ACS Publications) http://ift.tt/1SEPVmn

Saved: Heazlewoodite, Ni3S2: A Potent Catalyst for Oxygen Reduction to Water under Benign Conditions


Heazlewoodite, Ni3S2: A Potent Catalyst for Oxygen Reduction to Water under Benign Conditions by Joseph M. Falkowski, Nolan M. Concannon, Bing Yan and Yogesh Surendranath via Journal of the American Chemical Society: Latest Articles (ACS Publications) http://ift.tt/1fxzxWD

Jun 22, 2015

Multiple complexation of CO and related ligands to a main-group element

Full Article 

Transition metal–ligand fragments are often able to bind and release several carbon monoxide molecules, such as the catalysts used in industrial-scale acetic acid synthesis and the active sites of hydrogenase enzymes, but main-group elements have never shown an ability to bind more than one carbon monoxide molecule; here a boron-based compound stable to moisture and air is synthesized and shown to contain multiple carbon monoxide units bound to the central boron atom.

18 JUNE 2015 | VOL 522 | NATURE

 
Coherent x-rays image structural transformations in battery nanoparticles during electrochemical operation.

 

Abstract

Topological defects can markedly alter nanomaterial properties. This presents opportunities for “defect engineering,” where desired functionalities are generated through defect manipulation. However, imaging defects in working devices with nanoscale resolution remains elusive. We report three-dimensional imaging of dislocation dynamics in individual battery cathode nanoparticles under operando conditions using Bragg coherent diffractive imaging. Dislocations are static at room temperature and mobile during charge transport. During the structural phase transformation, the lithium-rich phase nucleates near the dislocation and spreads inhomogeneously. The dislocation field is a local probe of elastic properties, and we find that a region of the material exhibits a negative Poisson’s ratio at high voltage. Operando dislocation imaging thus opens a powerful avenue for facilitating improvement and rational design of nanostructured materials.
An aqueous micelle can stabilize separated charges created by photoinduced electron transfer for several days.

 

Abstract

The efficiency of biological photosynthesis results from the exquisite organization of photoactive elements that promote rapid movement of charge carriers out of a critical recombination range. If synthetic organic photovoltaic materials could mimic this assembly, charge separation and collection could be markedly enhanced. We show that micelle-forming cationic semiconducting polymers can coassemble in water with cationic fullerene derivatives to create photoinduced electron-transfer cascades that lead to exceptionally long-lived polarons. The stability of the polarons depends on the organization of the polymer-fullerene assembly. Properly designed assemblies can produce separated polaronic charges that are stable for days or weeks in aqueous solution.

Synthesis, Thermodynamic Studies, And Catalytic CO2 Hydrogenation Activity of [Rh(P2N2)2]+ Complexes

Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0358, United States
Beckman Institute, California Institute of Technology, 1200 East California Blvd., Pasadena, California 91125, United States
J. Am. Chem. Soc., Article ASAP
DOI: 10.1021/jacs.5b04291
Publication Date (Web): June 4, 2015

Abstract

Abstract Image
A series of five [Rh(P2N2)2]+ complexes (P2N2 = 1,5-diaza-3,7-diphosphacyclooctane) have been synthesized and characterized: [Rh(PPh2NPh2)2]+ (1), [Rh(PPh2NBn2)2]+ (2), [Rh(PPh2NPhOMe2)2]+ (3), [Rh(PCy2NPh2)2]+ (4), and [Rh(PCy2NPhOMe2)2]+ (5). Complexes 15 have been structurally characterized as square planar rhodium bis-diphosphine complexes with slight tetrahedral distortions. The corresponding hydride complexes 610 have also been synthesized and characterized, and X-ray diffraction studies of HRh(PPh2NBn2)2 (7), HRh(PPh2NPhOMe2)2 (8) and HRh(PCy2NPh2)2 (9) show that the hydrides have distorted trigonal bipyramidal geometries. Equilibration of complexes 25 with H2 in the presence of 2,8,9-triisopropyl-2,5,8,9-tetraaza-1-phosphabicyclo[3,3,3]undecane (Verkade’s base) enabled the determination of the hydricities and estimated pKa’s of the Rh(I) hydride complexes using the appropriate thermodynamic cycles. Complexes 15 were active for CO2 hydrogenation under mild conditions, and their relative rates were compared to that of [Rh(depe)2]+, a nonpendant-amine-containing complex with a similar hydricity to the [Rh(P2N2)2]+ complexes. It was determined that the added steric bulk of the amine groups on the P2N2 ligands hinders catalysis and that [Rh(depe)2]+ was the most active catalyst for hydrogenation of CO2 to formate.

Proton-Induced, Reversible Interconversion of a μ-1,2-Peroxo and a μ-1,1-Hydroperoxo Dicopper(II) Complex

Institut für Anorganische Chemie, Georg-August-Universität Göttingen, Tammannstraße 4, 37077 Göttingen, Germany
J. Am. Chem. Soc., Article ASAP
DOI: 10.1021/jacs.5b04361
Publication Date (Web): June 10, 2015

Abstract

Abstract Image
The μ-1,2-peroxo dicopper(II) complex (2) of a compartmental bis(tetradentate) pyrazolate-based ligand is shown to convert, upon protonation, to the corresponding μ-1,1-hydroperoxo dicopper(II) complex (3). The transformation is cleanly reversed with base, and an apparent pKa = 22.2 ± 0.3 for the Cu2OOH unit in MeCN has been determined. The unprecedented stability of 3 (t1/2 = 9 h in nitrile solvents at room temperature, giving the hydroxo-bridged dicopper complex) has allowed for its structural characterization by X-ray diffraction. While the O–O bond length (1.462(3) Å) barely changes upon protonation from 2 to 3, the O–O stretching frequency is much higher in the hydroperoxo complex 3 (860 cm–1). 3 mediates 2e oxo transfer to the nucleophilic substrate PPh3 but is not activated for H-atom abstraction.

Jun 17, 2015

Through-space transfer of chiral information mediated by a plasmonic nanomaterial


Through-space transfer of chiral information mediated by a plasmonic nanomaterial by Saeideh Ostovar pour via Nature Chemistry http://ift.tt/1JTukni http://ift.tt/1hvdawn

Nitrogen-Doping in ZnO via Combustion Synthesis?


Nitrogen-Doping in ZnO via Combustion Synthesis? by Stefan Söllradl, Magnus Greiwe, Vanessa J. Bukas, Magnus R. Buchner, Marc Widenmeyer, Timur Kandemir, Tobias Zweifel, Anatoliy Senyshyn, Sebastian Günther, Tom Nilges, Andreas Türler and Rainer Niewa via Chemistry of Materials: Latest Articles (ACS Publications) http://ift.tt/1Fv9A03 http://pubs.acs.org

Saved: Hydrothermal Growth and Photoelectrochemistry of Highly Oriented, Crystalline Anatase TiO2 Nanorods on Transparent Conducting Electrodes


Hydrothermal Growth and Photoelectrochemistry of Highly Oriented, Crystalline Anatase TiO2 Nanorods on Transparent Conducting Electrodes by Dong-Dong Qin, Ying-Pu Bi, Xin-Jian Feng, Wei Wang, Greg D. Barber, Ting Wang, Yu-Min Song, Xiao-Quan Lu and Thomas E. Mallouk via Chemistry of Materials: Latest Articles (ACS Publications) http://ift.tt/1deNYgI

Jun 16, 2015

Molybdenum-doped platinum-nickel nanocrystal catalysts exhibit high activity and durability for a key fuel cell reaction.

Abstract

Bimetallic platinum-nickel (Pt-Ni) nanostructures represent an emerging class of electrocatalysts for oxygen reduction reaction (ORR) in fuel cells, but practical applications have been limited by catalytic activity and durability. We surface-doped Pt3Ni octahedra supported on carbon with transition metals, termed M‐Pt3Ni/C, where M is vanadium, chromium, manganese, iron, cobalt, molybdenum (Mo), tungsten, or rhenium. The Mo‐Pt3Ni/C showed the best ORR performance, with a specific activity of 10.3 mA/cm2 and mass activity of 6.98 A/mgPt, which are 81- and 73‐fold enhancements compared with the commercial Pt/C catalyst (0.127 mA/cm2 and 0.096 A/mgPt). Theoretical calculations suggest that Mo prefers subsurface positions near the particle edges in vacuum and surface vertex/edge sites in oxidizing conditions, where it enhances both the performance and the stability of the Pt3Ni catalyst.
 
A new precursor library yields high-quality quantum dots for device applications [Also see Report by Hendricks et al.]
High-quality quantum dots with tunable particle size and composition are fabricated using inexpensive thioureas. [Also see Perspective by Hens]

Abstract

Controlling the size of colloidal nanocrystals is essential to optimizing their performance in optoelectronic devices, catalysis, and imaging applications. Traditional synthetic methods control size by terminating the growth, an approach that limits the reaction yield and causes batch-to-batch variability. Herein we report a library of thioureas whose substitution pattern tunes their conversion reactivity over more than five orders of magnitude and demonstrate that faster thiourea conversion kinetics increases the extent of crystal nucleation. Tunable kinetics thereby allows the nanocrystal concentration to be adjusted and a desired crystal size to be prepared at full conversion. Controlled precursor reactivity and quantitative conversion improve the batch-to-batch consistency of the final nanocrystal size at industrially relevant reaction scales.

 
An inorganic ring-shaped compound manifests electronic stabilization properties analogous to benzene’s.
  • Abstract
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  • Abstract

    Aromaticity is predominantly associated with carbon-rich compounds but can also occur in all-inorganic ones. We report the synthesis of the diphosphatriazolate anion, a rare example of a planar aromatic inorganic species. Treatment of azide (N3) in tetrahydrofuran solution with P2A2 (A = C14H10), a source of P2, produced P2N3, which we isolated as its [Na-kryptofix-221]+ salt in 22% yield and characterized by single-crystal x-ray diffraction. Salts [Na-kryptofix-221] [P2N3] and [Na-kryptofix-221] [P215NN2] were analyzed by infrared and Raman spectroscopy, 15N and 31P nuclear magnetic resonance spectroscopy, and mass spectrometry. The formation of the P2N3 anion was investigated using density functional theory, and its aromatic character was confirmed by NICS (nucleus-independent chemical shift) and QTAIM (quantum theory of atoms in molecules) methods.
     
A high-resolution structure provides insight into solar energy conversion during photosynthesis [Also see Research Article by Qin et al. ]

Tropolone as a High-Performance Robust Anchoring Group for Dye-Sensitized Solar Cells

Tropolone as a High-Performance Robust Anchoring Group for Dye-Sensitized Solar Cells

Dr. Tomohiro Higashino, Yamato Fujimori, Kenichi Sugiura, Yukihiro Tsuji, Prof. Dr. Seigo Ito and Prof. Dr. Hiroshi Imahori

Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto, Japan.
Graduate School of Engineering, University of Hyogo, 2167 Shosha, Himeji, Hyogo, Japan.
Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Nishikyo-ku, Kyoto, Japan
.

Higashino, T., Fujimori, Y., Sugiura, K., Tsuji, Y., Ito, S. and Imahori, H. (2015), Tropolone as a High-Performance Robust Anchoring Group for Dye-Sensitized Solar Cells. Angew. Chem. Int. Ed.. doi: 10.1002/anie.201502951

Abstract:

A tropolone group has been employed for the first time as an anchoring group for dye-sensitized solar cells (DSSCs). The DSSC based on a porphyrin, YD2-o-C8T, with a tropolone moiety exhibited a power-conversion efficiency of 7.7 %, which is only slightly lower than that observed for a reference porphyrin, YD2-o-C8, with a conventional carboxylic group. More importantly, YD2-o-C8T was found to be superior to YD2-o-C8 with respect to DSSC durability and binding ability to TiO2. These results unambiguously demonstrate that tropolone is a highly promising dye-anchoring group for DSSCs in terms of device durability as well as photovoltaic performance.