The active site of many non-noble metal cathodic oxygen reduction catalysts consists of a nitrogen-corodinated transition metal. Here, the authors report an iron-based electrocatalyst devoid of iron–nitrogen coordination, and demonstrate its high activity in acid and alkaline media.
Nature Communications doi: 10.1038/ncomms8343
Authors: Kara Strickland, Elise Miner, Qingying Jia, Urszula Tylus, Nagappan Ramaswamy, Wentao Liang, Moulay-Tahar Sougrati, Frédéric Jaouen, Sanjeev Mukerjee
Artificial photosynthesis is a means of harnessing solar energy to generate fuels but has traditionally been exploited for the generation of hydrogen. Here, Schreier et al . instead employ a perovskite photovoltaic device to effect the solar conversion of CO 2 to CO with high efficiency.
Nature Communications doi: 10.1038/ncomms8326
Authors: Marcel Schreier, Laura Curvat, Fabrizio Giordano, Ludmilla Steier, Antonio Abate, Shaik M. Zakeeruddin, Jingshan Luo, Matthew T. Mayer, Michael Grätzel
Palladium is an effective but expensive catalyst used in catalytic converters. Here, the authors show that defective Co 3 O 4 nanocrystals, synthesized via oxidation of carbon-encapsulated cobalt nanoparticles, display similar or even comparable catalytic activity to palladium for hydrocarbon combustion.
Nature Communications doi: 10.1038/ncomms8181
Authors: Han Wang, Chunlin Chen, Yexin Zhang, Lixia Peng, Song Ma, Teng Yang, Huaihong Guo, Zhidong Zhang, Dang Sheng Su, Jian Zhang
Despite intensive research on photochemical activation of sol–gel metal oxide materials, the relatively long processing time and lack of deep understanding of the underlying chemical courses have limited their broader impact on diverse materials and applications such as thin-film electronics, photovoltaics, and catalysts. Here, in-depth studies on the rapid photochemical activation of diverse sol–gel oxide films using various spectroscopic and electrical investigations for the underlying physicochemical mechanism are reported. Based on the exhaustive chemical and physical analysis, it is noted that deep ultraviolet-promoted rapid film formation such as densification, polycondensation, and impurity decomposition is possible within 5 min via in situ radical-mediated reactions. Finally, the rapid fabrication of all-solution metal oxide thin-film-transistor circuitry, which exhibits stable and reliable electrical performance with a mobility of >12 cm2 V−1 s−1 and an oscillation frequency of >650 kHz in 7-stage ring oscillator even after bending at a radius of <1 mm is demonstrated.
The general physicochemical mechanisms underlying photoactivated sol–gel reactions are described, with comprehensive chemical and structural analysis inducing rapid (<5 min) fabrication of various metal oxide films at low temperatures (<150 °C), and all-solution processed high-performance electronic devices and circuitry on ultrathin polymeric substrates are demonstrated. This will open new possibilities to prepare future electronic materials in a fast, scalable, and economic manner.
The 2D semiconductor MoS2 in its mono- and few-layer form is expected to have a significant exciton binding energy of several 100 meV, suggesting excitons as the primary photoexcited species. Nevertheless, even single layers show a strong photovoltaic effect and work as the active material in high sensitivity photodetectors, thus indicating efficient charge carrier photogeneration. Here, modulation spectroscopy in the sub-ps and ms time scales is used to study the photoexcitation dynamics in few-layer MoS2. The results suggest that the primary photoexcitations are excitons that efficiently dissociate into charges with a characteristic time of 700 fs. Based on these findings, simple suggestions for the design of efficient MoS2 photovoltaic and photodetector devices are made.
Few-layer MoS2 flakes are intermediates between conventional semiconductors and excitonic nanomaterials. By femtosecond optical pump–probe spectroscopy it is shown that photoexcitation creates excitons as the primary species. The excitons efficiently dissociate into charge carriers with a time constant of 700 fs, making few-layer MoS2 an excellent candidate for efficient photodetectors and photovoltaic devices.
The front cover demonstrates the fabrication of sol–gel derived metal oxide electronic devices and circuits by low-temperature photochemical activation via in-situ radical-mediated reactions. On page 2807, M.-H. Yoon, S. K. Park, and colleagues show that the rapid photoactivation process enables the conversion of the sol–gel precursors into metal oxide electronic materials directly on ultra-flexible plastic substrates, which will serve as a general methodology in a rapid, scalable, and economic manner.
Mammoth genomes provide recipe for creating Arctic elephants
Nature 521, 7550 (2015). http://www.nature.com/doifinder/10.1038/nature.2015.17462
Author: Ewen Callaway
Catalogue of genetic differences between woolly mammoths and elephants reveals how ice-age giants braved the cold.
Copper-exchanged SSZ-13 is a very efficient material in the selective catalytic reduction of NOx using ammonia (deNOx-SCR) and characterizing the underlying distribution of copper sites in the material is of prime importance to understand its activity. The IR spectrum of NO adsorbed to divalent copper sites are modeled using ab initio molecular dynamics simulations. For most sites, complex multi-peak spectra induced by the thermal motion of the cation as well as the adsorbate are found. A finite temperature spectrum for a specific catalyst was constructed, which shows excellent agreement with previously reported data. Additionally these findings allow active and inactive species in deNOx-SCR to be identified. To the best of our knowledge, this is the first time such complex spectra for single molecules adsorbed to single active centers have been reported in heterogeneous catalysis, and we expect similar effects to be important in a large number of systems with mobile active centers.
Theory and practice: The IR spectra of NO adsorbed on Cu centers in a copper-containing zeolite were modeled using molecular dynamics simulations. The spectra are complex, which is due to the thermal motions of the cations and the adsorbates, and are in excellent agreement with the experimental spectra.
Chemistry: Imaging of excited electron orbitals
Nature 519, 7544 (2015). doi:10.1038/519392d
A technique could pave the way for imaging electron behaviour as chemical reactions happen.Many reactions are governed by the behaviour of electrons in excited orbital states, but these states are difficult to capture because they last only a few picoseconds (10−12 seconds).
The future of the postdoc
Nature 520, 7546 (2015). http://www.nature.com/doifinder/10.1038/520144a
Author: Kendall Powell
There is a growing number of postdocs and few places in academia for them to go. But change could be on the way.
Poly(triazine imides) intercalated with Li+ and X− (PTI/X, X=Cl or Br), which are described widely as crystalline polymeric carbon nitrides, were synthesized in a facile manner by heating a mixture of melamine and LiX. This method has the advantages of low cost, scalable production, and high efficiency. Importantly, both PTI/Cl and PTI/Br exhibit an enhanced photocatalytic performance compared to conventional graphitic polymeric carbon nitride in the degradation of rhodamine B under visible-light irradiation because of their higher visible-light-harvesting ability and charge carrier separation efficiency.
Easy does it: Crystalline polymeric graphitic carbon nitrides with an enhanced visible-light-driven photocatalytic performance are prepared by heating a mixture of melamine and lithium halides.
The cover picture shows effective hydrogen production from an aqueous solution of ammonia-borane (NH3-BH3, AB) by bimetallic FeNi nanoparticles supported on CeO2. In their Full Paper, K. Mori, T. Taga, and H. Yamashita show highly dispersed and partially oxidized amorphous FeNi NPs stabilized by strong interaction with the CeO2 is active for the catalytic dehydrogenation of AB. The advantages of this catalytic system, such as the facile preparation method, free of noble metals, and high recyclability are particularly desirable for a hydrogen vector in terms of potential industrial application in fuel cells. The article highlighted by this cover can be found on p. 1285 ff. of Issue 8, 2015.