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Instruments / Technical Area	Publication Details	Published
I09-Surface and Interface Structural Analysis	Ni 3+ induced hole states enhance the oxygen evolution reaction activity of Ni x Co 3-x O 4 electrocatalysts Meiyan Cui , Xingyu Ding , Xiaochun Huang , Zechao Shen , Tien-lin Lee , Freddy E. Oropeza , Jan P. Hofmann , Emiel J. M. Hensen , Kelvin H. L. Zhang Chemistry Of Materials DOI: 10.1021/acs.chemmater.9b02453 Diamond Proposal Number(s): [21432] Show Abstract ▼ Abstract: This work reports a systematical study on the relationship of electronic structure to oxygen evolution reaction (OER) activity of NixCo3-xO4 (x=0-1) mixed oxides. The specific OER activity is substantially increased by 16 times from 0.02 mA cm-2BET for pure Co3O4 to 0.32 mA cm-2BET for x=1 at an overpotential of 0.4 V and exhibits a strong correlation with the amount of Ni ions in +3 oxidation state. X-ray spectroscopic study reveals that inclusion of Ni3+ ions upshifts the occupied valence band maximum (VBM) by 0.27 eV toward the Fermi level (EF), and creates a new hole (unoccupied) state located ~1 eV above the EF. Such electronic features favour the adsorption of OH surface intermediates on NixCo3-xO4, resulting in enhanced OER. Furthermore, the emerging hole state effectively reduces the energy barrier for electron transfer from 1.19 eV to 0.39 eV, and thereby improves the kinetics for OER. The electronic structure features that lead to a higher OER in NixCo3-xO4 can be extended to other transition metal oxides for rational design of highly active catalysts.	Aug 2019
I09-Surface and Interface Structural Analysis	Insights into the electronic structure of OsO 2 using soft and hard x-ray photoelectron spectroscopy in combination with density functional theory Anna Regoutz , Alex M. Ganose , Lars Blumenthal , Christoph Schlueter , Tien-lin Lee , Gregor Kieslich , Anthony K. Cheetham , Gwilherm Kerherve , Ying-sheng Huang , Ruei-san Chen , Giovanni Vinai , Tommaso Pincelli , Giancarlo Panaccione , Kelvin H. L. Zhang , Russell G. Egdell , Johannes Lischner , David O. Scanlon , David J. Payne Physical Review Materials 3 DOI: 10.1103/PhysRevMaterials.3.025001 Diamond Proposal Number(s): [12673] Show Abstract ▼ Abstract: Theory and experiment are combined to gain an understanding of the electronic properties of OsO2, a poorly studied metallic oxide that crystallizes in the rutile structure. Hard and soft valence-band x-ray photoemission spectra of OsO2 single crystals are in broad agreement with the results of density-functional-theory calculations, aside from a feature shifted to high binding energy of the conduction band. The energy shift corresponds to the conduction electron plasmon energy measured by reflection electron energy loss spectroscopy. The plasmon satellite is reproduced by many-body perturbation theory.	Feb 2019
I09-Surface and Interface Structural Analysis	Identification of lone pair surface states on indium oxide Daniel W. Davies , Aron Walsh , James J. Mudd , Chris F. Mcconville , Anna Regoutz , J. Matthias Kahk , David J. Payne , Vin R. Dhanak , David Hesp , Katariina Pussi , Tien-lin Lee , Russell G. Egdell , Kelvin H. L. Zhang The Journal Of Physical Chemistry C DOI: 10.1021/acs.jpcc.8b08623 Diamond Proposal Number(s): [8441] Show Abstract ▼ Abstract: Indium oxide is widely used as transparent electrode in optoelectronic devices and as a photocatalyst with activity for reduction of CO2. However, very little is known about the structural and electronic properties of its surfaces, particularly those prepared under reducing conditions. In this report, directional ‘lone-pair’ surface states associated with filled 5s2 orbitals have been identified on vacuum-annealed In2O3(111) through a combination of hard and soft X-ray photoemission spectroscopy and density functional theory calculations. The lone pairs reside on indium ad-atoms in a formal +1 oxidation state, each of which traps two electrons into a localised hybrid orbital protruding away from the surface and lying just above the valence band maximum in photoemission spectra. The third electron associated with the ad-atoms is delocalised into the conduction band, thus producing the surface electron accumulation layer identified previously on vacuum-annealed In2O3(111) (1×1) surfaces. The surface structure is further supported by low energy electron diffraction, but there is no chemical shift in indium core level x-ray photoelectron spectra between surface In(I) ad-atoms and bulk In(III). The 5s2 lone pairs confer Lewis basicity on the surface In sites and may have a pronounced impact on the catalytic or photo-catalytic activity of reduced In2O3.	Dec 2018
I16-Materials and Magnetism	Size-Dependent Shape and Tilt Transitions in In2O3 Nanoislands Grown on Cubic Y-Stabilized ZrO2(001) by Molecular Beam Epitaxy Kelvin H. L. Zhang , Anne Bourlange , Russell G. Egdell , Stephen P. Collins , Richard J. Bean , Ian K. Robinson , Roger A. Cowley Acs Nano 6 (8), 6717 - 6729 DOI: 10.1021/nn301382j Diamond Proposal Number(s): [503937] Show Abstract ▼ Abstract: The growth of In2O3 on cubic Y-stabilized ZrO2(001) by molecular beamepitaxy leads to formation of nanoscale islands which may tilt relative to the substrate in order to help accommodate the 1.7% tensile mismatch between the epilayer and the substrate. High-resolution synchrotron-based X-ray diffraction has been used in combination with atomic force microscopy to probe the evolution in island morphology, orientation, and tilt with island size. Very small islands formed at low substrate coverage are highly strained but exhibit no tilt, while intermediate islands are tilted randomly in all directions, giving rise to distinctive doughnut-shaped structure in three-dimensional reciprocal space isosurfaces. The largest islands with lateral sizes on the order of 1 μm tilt away from the four equivalent in-plane Æ110æ directions, giving three-dimensional scattering isosurfaces dominated by structure at the four corners of a square. Spatially resolved reciprocal space mapping using an X-ray beam with dimensions on the rder of 1 μm suggests that the four-fold symmetry observed using a larger beam arises from averaging over an ensemble of islands, each with an individual tilt down one direction, rather than from the coexistence of differently tilted domains within a given island.	Aug 2012

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