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

Note: Times Cited: 875 Reference EPFL-ARTICLE-206025doi:10.1021/cr0501846View record in Web of Science URL: ://WOS:000249839900009 Record created on 2015-03-03, modified on 2017-05-12

Complex Hydrides for Hydrogen Storage

: The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

More than 95% (in volume) of all of today’s chemical products are manufactured through catalytic processes, making research into more efficient catalytic materials a thrilling and very dynamic rese...

Metal–Organic Frameworks in Heterogeneous Catalysis: Recent Progress, New Trends, and Future Perspectives

International Tables for X-Ray Crystallography (Published for the International Union of Crystallography.) Vol. 1: Symmetry Groups. Edited by Norman F. M. Henry and Kathleen Lonsdale. Pp. xi + 558. (Birmingham: Kynoch Press, 1952.) 105s.

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International Tables for X-Ray Crystallography

The development of new metal-organic frameworks (MOFs) with dual functions of both water reduction and oxidation under visible-light irradiation is highly desirable for promising solar water splitting, but is not yet reported. Herein, a cadmium-based MOF (denoted as "Cd-TBAPy") single crystal with a 2D layered framework by employing 1,3,6,8-tetrakis(p-benzoic acid)pyrene (H4 TBAPy) as an organic linker is reported, which exhibits good visible-light absorption with edge of ≈600 nm. The Mott-Schottky (M-S) measurement and UV-vis analysis integrally reveal that the Cd-TBAPy is an n-type semiconductor with a bandgap of ≈2.15 eV whose conduction and valence band are estimated to be -0.05 and 2.10 eV, respectively. Together with loading of Pt or CoPi cocatalyst, the Cd-TBAPy is active for both water reduction and oxidation in the presence of scavengers under visible-light irradiation. Especially, the optimized apparent quantum efficiency for O2 evolution reaches 5.6% at 420 nm, much higher than that of previous MOF-based photocatalysts reported so far. This is thought to be the first MOF that functions as a photocatalyst for both water reduction and oxidation under visible light, demonstrating the intriguing future of MOF materials in solar-to-chemical energy conversion.

Visible-Light-Responsive 2D Cadmium–Organic Framework Single Crystals with Dual Functions of Water Reduction and Oxidation

Interfacial Charge Modulation: An Efficient Strategy for Boosting Spatial Charge Separation on Semiconductor Photocatalysts

The recent observation of room-temperature superconductivity will undoubtedly lead to a surge in the discovery of new, dense, hydrogen-rich materials. The rare earth metal superhydrides are predicted to have very high-T_{c} superconductivity that is tunable with changes in stoichiometry or doping. Here we report the synthesis of an yttrium superhydride that exhibits superconductivity at a critical temperature of 262 K at 182±8  GPa. A palladium thin film assists the synthesis by protecting the sputtered yttrium from oxidation and promoting subsequent hydrogenation. Phonon-mediated superconductivity is established by the observation of zero resistance, an isotope effect and the reduction of T_{c} under an external magnetic field. The upper critical magnetic field is 103 T at zero temperature.

Synthesis of Yttrium Superhydride Superconductor with a Transition Temperature up to 262 K by Catalytic Hydrogenation at High Pressures.

Electronic structures of zigzag edged graphene nanoribbons (ZGNRs) doped with boron (B) or nitrogen (N) atoms are investigated by spin polarized first-principles calculations. We find that ZGNRs can be tuned to be either semiconducting, half-metallic, or metallic by controlling the distance of the impurity atoms to the edges. A new scheme is identified to achieve full half-metallicity in ZGNRs by doping B atom at one edge and N atom at the other. We find that the origin of the half-metallicity is due to interaction between the edge states and B/N atoms which results in direct control over the electron occupation of the edge states. This mechanism is so robust that full half-metallicity can always be produced in ZGNRs irrespective of the ribbon width, which opens new possibilities for applications of ZGNRs in spintronic devices.

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Building Half-Metallicity in Graphene Nanoribbons by Direct Control over Edge States Occupation

Solar hydrogen peroxide (H2O2) produced through the selective two-electron (2e−) oxygen reduction pathway is an ideal alternative to liquid fuel in addition to being a versatile chemical. Up to now, low photocatalytic activity, low selectivity and serious competing reactions have been big hurdles in the production of solar H2O2 in an efficient way. Herein, we report that polyterthiophene (pTTh), a metal-free narrow-bandgap polymeric semiconductor, is an efficient photocathode for H2O2 production in alkaline solution. We found that 2e− selectivity for the ORR is dependent on the pH of electrolytes and approaches 100% at pH ∼ 13. A record-high H2O2 concentration of 110 mmol L−1 is achieved, which is two orders of magnitude higher than the previous photosynthesized H2O2. Furthermore, NiFeOx/BiVO4–pTTh dual-photoelectrodes in photoelectrochemical devices enabled bias-free synthesis of solar H2O2 of concentration ∼90 mmol L−1 for several cycles without any noticeable decay. This extremely high 2e− selectivity is attributed to the intrinsic electrochemical properties of pTTh. Theoretical calculations suggested that the selectivity-determining step in the 2e− process is over ∼200 times faster than that in the 4e− pathway. Our work paves an alternative way of generating liquid solar fuel that is very promising for practical applications.

Xiaoyu Wang

Papers

Visible-Light-Responsive 2D Cadmium–Organic Framework Single Crystals with Dual Functions of Water Reduction and Oxidation

Interfacial Charge Modulation: An Efficient Strategy for Boosting Spatial Charge Separation on Semiconductor Photocatalysts

Synthesis of Yttrium Superhydride Superconductor with a Transition Temperature up to 262 K by Catalytic Hydrogenation at High Pressures.

Building Half-Metallicity in Graphene Nanoribbons by Direct Control over Edge States Occupation

Efficient hydrogen peroxide synthesis by metal-free polyterthiophene via photoelectrocatalytic dioxygen reduction