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 ...

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

An electro-thermochemical cycling system for producing ammonia is provided that includes a reaction chamber having a metal compound input port, an anode suitable for oxidation in contact with the metal compound and configured for oxidation of hydroxide ions to water and oxygen, a cathode suitable for plating in contact with the metal compound and configured to electrolyze the metal compound to metal, a voltage source connecting the cathode and anode, a nitrogen port to the reaction chamber that combines nitrogen with the electrolyzed metal on the cathode to form a metal-nitrogen compound proximal to the nitrogen input, an atomic hydrogen port to the reaction chamber that combines with the metal-nitrogen compound to form ammonia, and an ammonia output port from the reaction chamber, where a metal compound input port inputs the metal compound to the reaction chamber according to a depletion rate of the metal compound in the reaction chamber

Electro-thermochemical Li cycling for NH3 synthesis from N2 and H2O

Cyclic voltammetry is a fundamental experimental tool for characterizing electrochemical surfaces Whereas cyclic voltammetry is widely used within the field of electrochemistry, a way to quantitatively and directly relate the cyclic voltammogram to ab initio calculations has been lacking, even for the simple case of electroadsorption and desorption of H In the following we derive the cyclic voltammogram for H adsorption and desorption on Pt(111) and Pt(100) based solely on density functional theory calculations and standard molecular tables The method will also be extended to include the potential dependence of the OH coverage during electrochemical water splitting on Pt(111) and Pt3Ni(111)

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Cyclic Voltammograms from First Principles

Oxygen chemisorption and incorporation on transition metal surfaces

A high-density ammonia storage/delivery system based on Mg(NH 3 ) 6 Cl 2 for ¿ in vehicles

A membrane-free electrochemical reactor and fuel-cell having a collection chamber between a first and second chamber, a mesoporous carbon paper cathode between the first chamber and the collection chamber, a mesoporous carbon paper anode between the second chamber and the collection chamber, the cathode is coated with an oxygen reduction reaction catalyst that imparts a two-electron partial reduction reaction to hydrogen peroxide, the anode is coated with an oxygen evolution reaction coating or a hydrogen oxidation reaction coating, oxygen/air input and output ports connected to the first chamber, KOH/water input and output ports connected to the second chamber that are in an open state under an electrolyzer mode, H2/water input and output ports connected to the second chamber that are in an open state under a fuel-cell mode, a second KOH/water input port connected to the collection chamber, and a hydrogen peroxide/KOH/water output port connected to the collection chamber.

Jens K. Nørskov

Papers

Electro-thermochemical Li cycling for NH3 synthesis from N2 and H2O

Cyclic Voltammograms from First Principles

Oxygen chemisorption and incorporation on transition metal surfaces

A high-density ammonia storage/delivery system based on Mg(NH 3 ) 6 Cl 2 for ¿ in vehicles

Electrochemical hydrogen peroxide generating device