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Photocatalysts: Nanosized crystal patchwork
generates hydrogen, raising alternative-energy hopes
By Mitch Jacoby
If water could be separated economically into oxygen and hydrogen, a clean-burning fuel, the world’s oceans would represent a free and virtually limitless feedstock for producing energy. A new strategy for designing light-activated catalysts that split water may help bring that alternative-energy goal a step closer to reality.
The interfaces between nanosized domains of α- and β-Ga2O3 mediate photocatalytic charge separation and water splitting.
Researchers in China have found that crystals of the semiconductor Ga2O3 that are composed of a patchwork of structurally distinct nanosized domains can split water photocatalytically (Angew. Chem. Int. Ed., DOI: 10.1002/anie.201207554). The study demonstrates that the interface between polymorphic crystal phases can play a key role in light-stimulated water splitting. The work may lead to photocatalysts that are more active than the relatively inefficient ones available today.
Photocatalysts split water by directing energy absorbed from light—often sunlight—to break water’s chemical bonds. The heart of the process is the light absorption event, which generates pairs of negatively charged electrons and positively charged holes (electron vacancies). The key to capitalizing on the energy absorbed from light is keeping the charges separated. Charge recombination can dissipate the absorbed energy before bonds are broken.
The standard strategy for maximizing charge separation in semiconductors calls for selectively doping the material to juxtapose positively (p-type) and negatively (n-type) charged regions. Researchers also make these types of interfaces, known as p-n junctions, by depositing two types of semiconductors side by side.
The new study, which was conducted by Xiang Wang, Can Li, and coworkers of the Dalian Institute of Chemical Physics, demonstrates an alternative way to keep charges separated. Rather than relying on p-n junctions to do the job, the Dalian team exploits the interfaces between structurally dissimilar nanosized domains of Ga2O3, which is known to crystallize in five polymorphic phases.
The researchers show that a simple heat treatment can be used to tailor the distribution of nanosized domains of Ga2O3’s so-called α and β phases. They further show that mixed α-β samples prepared by heating the starting material to roughly 600°C are up to seven times more catalytically active in splitting water than samples composed of either phase alone.
The University of Tokyo’s Kazunari Domen comments that although in this proof-of-concept study the overall activity of the Ga2O3 photocatalysts is not especially high, the strategy described here represents a new approach to boosting catalytic water-splitting efficiency. He adds that the method’s applicability may be limited, however, as a result of the relatively small number of materials known to exhibit similar kinds of polymorphs.
Iridium-catalyzed reaction creates
valuable scaffolds enantioselectively
By Bethany Halford
A new protocol for preparing polycyclic compounds enantioselectively promises to make it easier to build these pharmaceutically relevant scaffolds (J. Am. Chem. Soc., DOI: 10.1021/ja310386m). The reaction, developed by Erick M. Carreira and coworkers at the Swiss Federal Institute of Technology, Zurich, uses an iridium-based catalyst and a zinc triflate promoter to coax the cascade reaction of polyenes (example shown). To begin the cascade, a racemic allylic alcohol within the polyene structure reacts with an iridium catalyst. This interaction appears to dictate the stereochemistry of the first cyclization. Subsequent cyclizations are effectively encoded in the first ring, the researchers believe. Using the protocol, Carreira and colleagues prepared nine polycyclic compounds—including heterocycles—in good yields, with enantiomeric excesses reaching 99%. “It is important to note that all the reactions are conducted at ambient temperature with commercial-grade solvents and reagents, making this cyclization protocol convenient to perform,” the chemists point out.
Tomography method monitors changes
in chemically distinct nanoscale regions of catalysts under reaction conditions
By Mitch Jacoby
Thanks to a specially designed reactor cell, researchers can now probe changes in the chemical composition, morphology, porosity, and other properties of individual 20-μm-sized catalyst particles as the particles mediate chemical reactions (Angew. Chem. Int. Ed., DOI: 10.1002/anie.201204930).
The study conducted by Joy C. Andrews of SLAC National Accelerator Laboratory; Bert M. Weckhuysen of Utrecht University, in the Netherlands; and coworkers demonstrates a procedure for exploiting high-energy X-ray microscopy to penetrate deeply into complex materials and resolve chemically distinct nanoscale regions within their bulk. Solid catalysts often undergo substantial changes—sometimes beneficial, sometimes detrimental—upon exposure to reactive chemicals at high temperature and pressure. Mapping those changes in three dimensions as they occur could lead to improved catalysts, but capturing the information remains challenging. To demonstrate the new method’s capabilities, the team probed a model Fischer-Tropsch C–C coupling catalyst as it was exposed to 10 atm of a mixture of H2 and CO at 350°C. The method pinpointed regions rich in Fe2O3, Fe2TiO5, Fe3O4, ZnO, and K2O and monitored the evolution of those regions over the course of several hours.
Chemical & Engineering News
Applied Catalysis A: General
Nanocatalysts for conversion of natural gas to liquid fuels and petrochemical feedstocks. Review article
M. Gharibi, F.T. Zangeneh, F. Yaripour, S. Sahebdelfar
http://www.sciencedirect.com/science/article/pii/S0926860X12004036
Fischer-Tropsch synthesis: Effect of Pd, Pt, Re, and Ru noble metal promoters on the activity and selectivity
of a 25%Co/Al2O3 catalyst
W. Ma, G. Jacobs, R.A. Keogh, D.B. Bukur, B.H. Davis
http://www.sciencedirect.com/science/article/pii/S0926860X12003183
Applied Catalysis B: Environmental
Mn-Fe/ZSM5 as a low-temperature SCR catalyst to remove NOx from diesel engine exhaust
Y.J. Kim, H.J. Kwon, I. Heo, I.S. Nam, B.K. Cho, J.W. Choung, M.S. Cha, G.K. Yeo
http://www.sciencedirect.com/science/article/pii/S0926337312002639
Improved visible light photocatalytic activity of TiO2 co-doped with vanadium and nitrogen
Jaiswal, R.; Patel, N.; Kothari, D.C.; Miotello, A.
http://www.sciencedirect.com/science/article/pii/S0926337312002974
Catalysis Today
The past, present and future of heterogeneous catalysis
I. Fechete, Y. Wang, J.C. Vedrine
http://www.sciencedirect.com/science/article/pii/S0920586112002751
Main technologies in biodiesel production: State of the art and future challenges. Review article
E. Santacesaria, G.M. Vicente, M. Di Serio, R. Tesser
http://www.sciencedirect.com/science/article/pii/S0920586112003446
Chemical Engineering Journal
Modified oil palm leaves adsorbent with enhanced hydrophobicity for crude oil removal
S.M. Sidik, A.A. Jalil, S. Triwahyono, S.H. Adam, M.A.H. Satar, B.H. Hameed
http://www.sciencedirect.com/science/article/pii/S1385894712008625
Journal of Catalysis
CO hydrogenation to methanol on Cu-Ni catalysts: Theory and experiment
F. Studt, F. Abild-Pedersen, Q. Wu, A.D. Jensen, B. Temel, J.D. Grunwaldt, J.K. Norskov
http://www.sciencedirect.com/science/article/pii/S0021951712001765
ChemCatChem
Simultaneous Generation of Mesoxalic Acid and Electricity from Glycerol on a Gold Anode Catalyst
in Anion-Exchange Membrane Fuel Cells
Le Xin, Zhiyong Zhang, Zhichao Wang, Wenzhen Li
http://onlinelibrary.wiley.com/doi/10.1002/cctc.201200017/full
ChemSusChem
An Intermolecular Heterobimetallic system for Photocatalytic Water Reduction
Sven Hansen, Marcus Klahn, Torsten Beweries, Uwe Rosenthal
http://onlinelibrary.wiley.com/doi/10.1002/cssc.201100794/full
Advanced Synthesis & Catalysis
Catalytic Asymmetric Epoxidation of 2-Cyclopentenones
Carl A. Busacca, Daniel R. Fandrick, Jinhua J. Song, Chris H. Senanayake
http://onlinelibrary.wiley.com/doi/10.1002/adsc.201200072/full
Angewandte Chemie International Edition
Electronic Modulation of a Copper/Zinc Oxide Catalyst by a Heterojunction for Selective Hydrogenation
of Carbon Dioxide to Methanol
Fenglin Liao, Ziyan Zeng, Clive Eley, Qin Lu, Xinlin Hong, Shik Chi Edman Tsang
http://onlinelibrary.wiley.com/doi/10.1002/anie.201200903/full
Applied Organometallic Chemistry
Mixed metal MgO–ZrO2 nanoparticle-catalyzed O-tert-Boc protection of alcohols and phenols under solvent-free conditions
Manoj B. Gawande, Sharad N. Shelke, Paula S. Branco, Anuj Rathi and Rajesh K. Pandey
http://onlinelibrary.wiley.com/doi/10.1002/aoc.2846/full
Chemical Engineering and Technology
Testing of a Ni-Al2O3 Catalyst for Methane Steam Reforming Using Different Reaction Systems
N. de Miguel, J. Manzanedo, P. L. Arias
http://onlinelibrary.wiley.com/doi/10.1002/ceat.201100348/pdf
Asia-Pacific Journal of Chemical Engineering
Application of clean technologies using electrochemistry in ionic liquids
A.P. Doherty, L. Diaconu, E. Marley, P. L. Spedding, R. Barhdadi, M. Troupel
http://onlinelibrary.wiley.com/doi/10.1002/apj.529/pdf
Chemistry – A European Journal
Bimetallic Catalysis using Transition and Group 11 Metals: An Emerging Tool for C-C Coupling and Other Reactions
M. H. Pérez-Temprano, J. A. Casares, P. Espinet
http://onlinelibrary.wiley.com/doi/10.1002/chem.201102888/full
Journal of Chemical Technology and Biotechnology
Heterogeneously catalyzing C-C coupling reactions with precious metal nanoparticles
Simon K. Beaumont
http://onlinelibrary.wiley.com/doi/10.1002/jctb.3748/full
Helvetica Chimica Acta
Substrate Range of the Titanium TADDOLate Catalyzed Asymmetric Fluorination of Activated Carbonyl Compounds
Andreas Bertogg, Lukas Hintermann, Dominique P. Huber, Mauro Perseghini, Maria Sanna, Antonio Togni
http://onlinelibrary.wiley.com/doi/10.1002/hlca.201100375/pdf
Macromolecular Reaction Engineering
Effect of Hydrogen and External Donor on Propylene Polymerization Kinetics with a 4th-Generation Ziegler-Natta Catalyst
Ahmad Alshaiban, João B. P. Soares
http://onlinelibrary.wiley.com/doi/10.1002/mren.201200002/full
Macromolecular Chemistry and Physics
Poly(ε-caprolactone) by Combined Ring-Opening Polymerization and Polycondensation
Hans R. Kricheldorf, Steffen M. Weidner, Felix Scheliga, Mohammed Lahcini
http://onlinelibrary.wiley.com/doi/10.1002/macp.201200061/full
Israel Journal of Chemistry
Asymmetric Autocatalysis Triggered by Chiral Crystals Formed from Achiral Compounds and Chiral Isotopomers
Tsuneomi Kawasaki, Kenso Soai
http://onlinelibrary.wiley.com/doi/10.1002/ijch.201100155/full
Chinese Journal of Chemistry
Friedel-Crafts Alkylation of Indoles with Nitroalkenes Catalyzed by Zn(II)-Thiourea Complex
Ningning Wan, Yonghai Hui, Zhengfeng Xie, Jide Wang
http://onlinelibrary.wiley.com/doi/10.1002/cjoc.201180480/pdf
Journal of the Chinese Chemical Society
Control of Catalytic Activity Via Porosity, Chemical Composition, and Morphology of Nanostructured Porous
Manganese Oxide Materials
Chun-Hu Chen, Steven L. Suib
http://onlinelibrary.wiley.com/doi/10.1002/jccs.201100699/pdf
WIRES: Computational Molecular Science
A refinement of everyday thinking: the energetic span model for kinetic assessment of catalytic cycles
Sebastian Kozuch
http://onlinelibrary.wiley.com/doi/10.1002/wcms.1100/full
Zeitschrift für anorganische und allgemeine Chemie
Synthesis of a Water-Stable 2, 4-Bis(trifluoromethyl)phenyl-Substituted Phosphonous Acid Palladium Complex
and its Catalytic Activity in Cross-Coupling Reactions
Boris Kurscheid, Hans-Georg Stammler, Beate Neumann, Berthold Hoge
http://onlinelibrary.wiley.com/doi/10.1002/zaac.201100344/full
The Chemical Record
Design of Molecular Catalysts for Achievement of High Turnover Number in Homogeneous Hydrogenation
Noriyoshi Arai, Takeshi Ohkuma
http://onlinelibrary.wiley.com/doi/10.1002/tcr.201100019/full
European Journal of Organic Chemistry
Biocatalytic Approaches to the Henry (Nitroaldol) Reaction
Sinéad E. Milner, Thomas S. Moody, Anita R. Maguire
http://onlinelibrary.wiley.com/doi/10.1002/ejoc.201101840/full
European Journal of Inorganic Chemistry
Cooperative Catalysis with First-Row Late Transition Metals
Jarl Ivar van der Vlugt
http://onlinelibrary.wiley.com/doi/10.1002/ejic.201100752/full
ChemPhysChem
The Role of Effective Mass of Carrier in the Photocatalytic Behavior of Silver Halide-Based Ag@AgX (X=Cl, Br, I):
A Theoretical Study
Xiangchao Ma, Ying Dai, Meng Guo, Baibiao Huang
http://onlinelibrary.wiley.com/doi/10.1002/cphc.201200159/full
Aiche Journal
Multiscale modeling for emergent behavior, complexity, and combinatorial explosion
Dionisios G. Vlachos
http://onlinelibrary.wiley.com/doi/10.1002/aic.13803/full
The Canadian Journal of Chemical Engineering
Evolving applications of zeolite molecular sieves
Christopher C. H. Lin, K. Amy Dambrowitz, Steven M. Kuznicki
http://onlinelibrary.wiley.com/doi/10.1002/cjce.20667/pdf
Journal of Peptide Science
Peptides as asymmetric catalysts and templates for the controlled formation of Ag nanoparticles
Helma Wennemers
http://onlinelibrary.wiley.com/doi/10.1002/psc.2422/full
Chemie Ingenieur Technik
New Catalysts for the Hydrogenation of Glucose to Sorbitol
Reinhard Geyer, Peter Kraak, Axel Pachulski, Rainer Schödel
http://onlinelibrary.wiley.com/doi/10.1002/cite.201100108/pdf