Photocatalytic Partial Water Oxidation Promoted by a Hydrogen Acceptor-Hydroxyl Mediator Couple.

Hydrogen peroxide (HO) is an important chemical in synthetic chemistry with huge demands. Photocatalytic synthesis of HO via oxygen reduction and water oxidation reactions (ORR and WOR) is considered as a promising and desirable solution for on-site applications. However, the efficiency of such a process is low due to the poor solubility of molecular oxygen and the rapid reverse reaction of hydroxyl radicals (OH) with hydrogen atoms (H).

Photocatalytic Abstraction of Hydrogen Atoms from Water Using Hydroxylated Graphitic Carbon Nitride for Hydrogenative Coupling Reactions.

Employing pure water, the ultimate green source of hydrogen donor to initiate chemical reactions that involve a hydrogen atom transfer (HAT) step is fascinating but challenging due to its large H-O bond dissociation energy (BDE =5.1 eV). Many approaches have been explored to stimulate water for hydrogenative reactions, but the efficiency and productivity still require significant enhancement.

Contrasting Efficiency of Electron-Induced Reaction at Cu(110) in Aliphatic and Aromatic Bromides.

We report a comparative study of the electron-induced reaction of pentyl bromide (PeBr) and phenyl bromide (PhBr) on Cu(110) at 4.6 K, observed by scanning tunneling microscopy (STM). The induced dissociation of the intact adsorbed molecule for both reagents occurred at an energy of 2.

Boosting Photocatalytic Hydrogen Production by Modulating Recombination Modes and Proton Adsorption Energy.

Solar-driven production of renewable energy (e.g., H) has been investigated for decades.

Light-tuned selective photosynthesis of azo- and azoxy-aromatics using graphitic CN.

Solar-driven photocatalysis has attracted significant attention in water splitting, CO reduction and organic synthesis. The syntheses of valuable azo- and azoxyaromatic dyes via selective photoreduction of nitroaromatic compounds have been realised using supported plasmonic metal nanoparticles at elevated temperatures (≥90 °C); however, the high cost, low efficiency and poor selectivity of such catalyst systems at room temperature limit their application. Here we demonstrate that the inexpensive graphitic CN is an efficient photocatalyst for selective syntheses of a series of azo- and azoxy-aromatic compounds from their corresponding nitroaromatics under either purple (410 nm) or blue light (450 nm) excitation.

Photosystem II Acts as a Spin-Controlled Electron Gate during Oxygen Formation and Evolution.

The oxygen evolution complex (OEC) of photosystem II (PSII) is intrinsically more active than any synthetic alternative for the oxygen evolution reaction (OER). A crucial question to solve for the progress of artificial photosynthesis is to understand the influential interactions during water oxidation in PSII. We study the principles of interatomic electron transfer steps in OER, with emphasis on exchange interactions, revealing the influence of delocalizing ferromagnetic spin potentials during the catalytic process.

Nondestructive imaging of atomically thin nanostructures buried in silicon.

It is now possible to create atomically thin regions of dopant atoms in silicon patterned with lateral dimensions ranging from the atomic scale (angstroms) to micrometers. These structures are building blocks of quantum devices for physics research and they are likely also to serve as key components of devices for next-generation classical and quantum information processing. Until now, the characteristics of buried dopant nanostructures could only be inferred from destructive techniques and/or the performance of the final electronic device; this severely limits engineering and manufacture of real-world devices based on atomic-scale lithography.

Vibrational excitation induces double reaction.

Electron-induced reaction at metal surfaces is currently the subject of extensive study. Here, we broaden the range of experimentation to a comparison of vibrational excitation with electronic excitation, for reaction of the same molecule at the same clean metal surface. In a previous study of electron-induced reaction by scanning tunneling microscopy (STM), we examined the dynamics of the concurrent breaking of the two C-I bonds of ortho-diiodobenzene physisorbed on Cu(110).

Single-electron induces double-reaction by charge delocalization.

Injecting an electron by scanning tunneling microscope into a molecule physisorbed at a surface can induce dissociative reaction of one adsorbate bond. Here we show experimentally that a single low-energy electron incident on ortho-diiodobenzene physisorbed on Cu(110) preferentially induces reaction of both of the C-I bonds in the adsorbate, with an order-of-magnitude greater efficiency than for comparable cases of single bond breaking. A two-electronic-state model was used to follow the dynamics, first on an anionic potential-energy surface (pes*) and subsequently on the ground state pes.

Localized reaction at a smooth metal surface: p-diiodobenzene at Cu(110).

Halogenation at a semiconductor surface follows simple dynamics characterized by "localized reaction" along the direction of the halide bond being broken. Here we extend the study of halide reaction dynamics to the important environment of a smooth metal surface, where greater product mobility would be expected. Extensive examination of the physisorbed reagent and chemisorbed products from two successive electron-induced reactions showed, surprisingly, that for this system product localization and directionality described the dynamics at a metal.

Molecular calipers control atomic separation at a metal surface.

If a molecule controls the length of some other moiety, it can be termed a "molecular caliper". Here we image individual molecular calipers of this type by scanning tunneling microscopy. These consist of linear polymers of p-diiodobenzene, (pDIB)n, of varying length, 0.

Surface-mediated chain reaction through dissociative attachment.

Chain reactions on a surface offer an important route to linear nanopatterning. We recently reported cooperative reactions on a silicon surface in which the reaction of one halogen atom with a silicon atom of a silicon dimer induced the halogenation of its neighbouring silicon atom through surface-mediated charge transfer. The reaction was unable to propagate further but here we describe how, by chemically bridging the gaps between the rows of these silicon dimers, this mechanism is able to form extended chains.

Dipole-directed assembly of lines of 1,5-dichloropentane on silicon substrates by displacement of surface charge.

One-dimensional nanostructures at silicon surfaces have potential applications in nanoscale devices. Here we propose a mechanism of dipole-directed assembly for the growth of lines of physisorbed dipolar molecules. The adsorbate chosen was a halide, in preparation for the patterned imprinting of halogen atoms.