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

Correlation between sticking probability and adsorbate-induced electron structure

Density Functional Calculations of N2Adsorption and Dissociation on a Ru(0001) Surface

We present a density-functional-theory study of formaldehyde and methanol synthesis from CO and H2 on a Ni catalyst We investigate the intermediate products of the reaction and calculate the reaction enthalpy and energy barrier for each elementary reaction, taking into account several different adsorption geometries and the presence of isomers of the intermediate products Hydrogenation of CO is favored over desorption or dissociation of CO on flat Ni(111), to form the formyl radical (HCO) or its isomer, COH Subsequent hydrogenation leads to formaldehyde (CH2O), methoxy (CH3O), and, finally, methanol (CH3OH) The overall reaction barrier for formaldehyde and methanol formation is 20 eV

DFT Study of Formaldehyde and Methanol Synthesis from CO and H2 on Ni(111)

https://digital.library.unt.edu/ark:/67531/metadc846463/m2/1/high_res_d/1022510.pdf

Scaling relationships for adsorption energies of C2 hydrocarbons on transition metal surfaces

Solid surfaces are used extensively as catalysts throughout the chemical industry, in the energy sector, and in environmental protection. Recently, density functional theory has started providing new insight into the atomic-scale mechanisms of heterogeneous catalysis, helping to interpret the large amount of experimental data gathered during the last decades. This article shows how density functional theory can be used to describe the state of the surface during reactions and the rate of catalytic reactions. It will also show how we are beginning to understand the variation in catalytic activity from one transition metal to the next. Finally, the prospects of using calculations to guide the development of new catalysts in industry will be discussed.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0883769400011222

Jens K. Nørskov

Papers

Correlation between sticking probability and adsorbate-induced electron structure

Density Functional Calculations of N2Adsorption and Dissociation on a Ru(0001) Surface

DFT Study of Formaldehyde and Methanol Synthesis from CO and H2 on Ni(111)

Scaling relationships for adsorption energies of C2 hydrocarbons on transition metal surfaces

Density Functional Theory in Surface Science and Heterogeneous Catalysis