There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Single-layer metal dichalcogenides are two-dimensional semiconductors that present strong potential for electronic and sensing applications complementary to that of graphene.

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Electronics and optoelectronics of two-dimensional transition metal dichalcogenides.

Energy harvested directly from sunlight offers a desirable approach toward fulfilling, with minimal environmental impact, the need for clean energy. Solar energy is a decentralized and inexhaustible natural resource, with the magnitude of the available solar power striking the earth’s surface at any one instant equal to 130 million 500 MW power plants.1 However, several important goals need to be met to fully utilize solar energy for the global energy demand. First, the means for solar energy conversion, storage, and distribution should be environmentally benign, i.e. protecting ecosystems instead of steadily weakening them. The next important goal is to provide a stable, constant energy flux. Due to the daily and seasonal variability in renewable energy sources such as sunlight, energy harvested from the sun needs to be efficiently converted into chemical fuel that can be stored, transported, and used upon demand. The biggest challenge is whether or not these goals can be met in a costeffective way on the terawatt scale.2

http://pubs.acs.org/doi/pdf/10.1021/cr1002326

Solar Water Splitting Cells

Ultrathin two-dimensional nanosheets of layered transition metal dichalcogenides (TMDs) are fundamentally and technologically intriguing. In contrast to the graphene sheet, they are chemically versatile. Mono- or few-layered TMDs - obtained either through exfoliation of bulk materials or bottom-up syntheses - are direct-gap semiconductors whose bandgap energy, as well as carrier type (n- or p-type), varies between compounds depending on their composition, structure and dimensionality. In this Review, we describe how the tunable electronic structure of TMDs makes them attractive for a variety of applications. They have been investigated as chemically active electrocatalysts for hydrogen evolution and hydrosulfurization, as well as electrically active materials in opto-electronics. Their morphologies and properties are also useful for energy storage applications such as electrodes for Li-ion batteries and supercapacitors.

http://nanotubes.rutgers.edu/PDFs/nchem_TMDs_2013.pdf

The chemistry of two-dimensional layered transition metal dichalcogenide nanosheets

We present a method for calculating the stability of reaction intermediates of electrochemical processes on the basis of electronic structure calculations. We used that method in combination with detailed density functional calculations to develop a detailed description of the free-energy landscape of the electrochemical oxygen reduction reaction over Pt(111) as a function of applied bias. This allowed us to identify the origin of the overpotential found for this reaction. Adsorbed oxygen and hydroxyl are found to be very stable intermediates at potentials close to equilibrium, and the calculated rate constant for the activated proton/electron transfer to adsorbed oxygen or hydroxyl can account quantitatively for the observed kinetics. On the basis of a database of calculated oxygen and hydroxyl adsorption energies, the trends in the oxygen reduction rate for a large number of different transition and noble metals can be accounted for. Alternative reaction mechanisms involving proton/electron transfer to ...

/pdf/origin-of-the-overpotential-for-oxygen-reduction-at-a-fuel-jdt5gxiyj8.pdf

Origin of the Overpotential for Oxygen Reduction at a Fuel-Cell Cathode

Computational materials design from first principles

Coal-to-Gas: New Methanation Catalysts Discovered by Combining Computational and Experimental Methods

Calculations of the adiabatic potential energy surface for atoms and molecules interacting with metal surfaces based on the effective medium theory are reviewed. For atomic chemisorption, the full potential energy surface has been calculated in a number of cases and the properties of the interaction potential can be related to the parameters describing the atom and surface in question. For molecular chemisorption and surface reactions, the effective medium theory can be used to make comparisons between binding energies and activation energies.

Adsorbate-Surface Interactions

In this work, we suggest a strategy of tuning the adsorbate binding strength by tailoring core-shell nanostructures. To do this, two major effects are utilized: the over-weakening of binding for thin shell systems, and the strengthening of binding on undercoordinated sites found commonly on nanoparticles. It has been shown that single monolayers of platinum supported on various substrates can exhibi t properties drastically different from platinum in its bulk form. In particular, one monolayer of platinum on ruthenium has been shown to have a much weaker PtO bond on the terrace (111) sites . However, by adding additional layers of platinum the effect is lessened and the O-Pt/Ru bond is strengthened [4,5]. Further significant strengthening of the binding will occur when moving from terrace sites to undercoordinated edge and corner sites which are prevalent in high surface area nanoparticulate catalysts.

http://ma.ecsdl.org/content/MA2013-02/15/1437.full.pdf

Jens K. Nørskov

Papers

Computational materials design from first principles

Coal-to-Gas: New Methanation Catalysts Discovered by Combining Computational and Experimental Methods

Adsorbate-Surface Interactions

Ru@Pt Core-Shell Catalysts for the Oxygen Reduction Reaction (ORR), a New Framework for Tuning Binding Energies

Surface science lettersThe onset of disorder in Al(110) surfaces below the melting point