Lithium and oxygen adsorption at MnO2 (110) surface
Publication date: 26 November 2013
The adsorption and co-adsorption of lithium and oxygen at the surface of rutile-like manganese dioxide (β-MnO2), which are important in the context of Li–air batteries, are investigated using density functional theory. In the absence of lithium, the most stable surface of β-MnO2, the (110), adsorbs oxygen in the form of peroxo groups bridging between two manganese cations. Conversely, in the absence of excess oxygen, lithium atoms adsorb on the (110) surface at two different sites, which are both tri-coordinated to surface oxygen anions, and the adsorption always involves the transfer of one electron from the adatom to one of the five-coordinated manganese cations at the surface, creating (formally) Li+ and Mn3+ species. The co-adsorption of lithium and oxygen leads to the formation of a surface oxide, involving the dissociation of the O2 molecule, where the O adatoms saturate the coordination of surface Mn cations and also bind to the Li adatoms. This process is energetically more favourable than the formation of gas-phase lithium peroxide (Li2O2) monomers, but less favourable than the formation of Li2O2 bulk. These results suggest that the presence of β-MnO2 in the cathode of a non-aqueous Li–O2 battery lowers the energy for the initial reduction of oxygen during cell discharge.
Designer Piercings: New membrane pores with DNA nanotechnology
Publication date: 6 November 2013
Au- and Pt-Nanoparticle-Functionalized Tungsten Oxide Nanoneedles for Selective Gas Microsensor Arrays
Publication date: 19 March 2013
Chris Blackman demonstrates a new gas-phase method for the one-step synthesis of metal nanoparticles supported on nanostructured metal oxides as a featured cover article in Advanced Functional Materials. With no requirement for substrate pre-treatment, this provides for direct integration of the co-deposited nanomaterial with device structures and it is utilized for the fabrication of selective gas microsensor arrays based on gold and platinum decorated tungsten oxide nanorods.
Activation of Carbon Dioxide over Zinc Oxide by Localised Electrons
Publication date: 5 November 2012
ACS Present Department with John William Draper medal
Publication date: 4 September 2012
John William Draper – When the College opened in 1828, the Professor of Chemistry who was appointed was Edward Turner. One of his students was John William Draper who later emigrated to the United States and became professor of chemistry at New York University. He had a distinguished career, particularly in the new field of photography. He was the first to photograph the moon (1840) and the Great Orion Galaxy (1880), and he is known as the first astrophotographer.
Ice structures, patterns, and processes: A view across the icefields
Publication date: 28 August 2012
Perspective: Quo Vadis, agostic bonding?
Publication date: 30 January 2012
The Use of Combinatorial Aerosol-Assisted Chemical Vapour Deposition for the Formation of Gallium-Indium-Oxide Thin Films
Publication date: 23 September 2011
This paper describes the use of combinatorial aerosol-assisted chemical vapour deposition (cAACVD) to deposit gallium-doped indium oxide thin films. The oxide films, GaxIn2-xO3, were deposited within composition graduated films from the aerosol-assisted CVD of GaMe3, InMe3 and HOCH2CH2OMe. Amorphous Ga2O3 was deposited closest to the inlet from the bubbler containing GaMe3/HOCH2CH2OMe whereas crystalline In2O3 was grown on the substrate closest to the inlet from the bubbler containing InMe3/HOCH2CH2OMe. A range of gallium-indium-oxide compositions, GaxIn2-xO3, were deposited on the substrate in the region between the two inlets. This allowed for a systematic investigation on the effect of doping on gallium and indium oxide and a direct relationship between composition and conductivity of the films was observed. This new technique combines the advantages of AACVD (volatility/thermal stability restrictions are removed) with those of cAPCVD/cLPCVD (rapid deposition/analysis of a compositional gradient). By utilizing a liquid-gas aerosol, as is employed in combinatorial AACVD, the restrictions of volatility and thermal stability are lifted and so new precursors and materials can be investigated.
New fundamental insight into the structure of ice
Publication date: 14 September 2011
Ice exhibits a phenomenon known as pre-melting which was first alluded to by Michael Faraday in his ‘regelation’ experiments at the Royal Institution in the 1850’s. A liquid like layer forms at the surface of ice, but there is dispute about the temperature at which this layer first occurs. Understanding the structure of the layer and its temperature dependence is important in the context of atmospheric heterogeneous catalysis, because the surface of ice particulates facilitate reactions of radicals and trace gases in the atmosphere.
In a recent paper in Nature Materials, researchers from UCL (Matt Watkins, Angelos Michaelides and Ben Slater) in collaboration with researchers from University of Zurich, Peking University and the Chinese Academy of Sciences have discovered unexpected properties of ice at the nanoscale that relate to Faraday’s experiments. Using density functional theory calculations, they discovered each molecule is bound to the surface by a different force, unlike most crystalline materials where each surface molecule has an identical binding energy. A fraction of the surface molecules are so weakly bound that they are easily displaced to form an overlayer, leading to less crystalline surface layers. The figure illustrates the variation in binding energy, which arises from the interaction of the water’s dipole within a geometrically frustrated array of neighbouring dipole moments.
Figure: A view of the ice surface illustrating weakly, (red), intermediate (white) and strongly bound water molecules (blue). White molecules are at the external surface, grey lie sub-surface.
Computer simulations revealing how salt crystals dissolve in water featured on the cover of PCCP
Publication date: 1 August 2011
Computer simulations reveal in the most exquisite detail how salt crystals dissolve in water.
Salt dissolution has a resonance with scientists and non-scientists alike being a piece of “chemistry” exploited daily to inhibit the freezing or accelerate the boiling of water. Despite this key role and increased contemporary drivers from e.g. nanotechnology and the desalination industry, the mechanism of salt dissolution has however remained elusive.