Boosting the methanol selectivity in CO hydrogenation over a MOF-derived CuZn@CN catalyst Rb incorporation.

The highly selective hydrogenation of CO to methanol has been achieved through the simultaneous utilization of alkali metals and Co as promoters over Cu-Zn@CN catalysts derived from MOF. Rb facilitates the dissociation of CO in the aqueous phase at relatively mild conditions to yield methanol with a selectivity of 89%.

Insights into the electronic structure of hydroxyl on Ag(110) under near ambient conditions.

Adsorbed hydroxyl is a key intermediate present in many catalytic reactions and electrochemical processes. In particular, hydroxyl adsorbed on noble metal surfaces has attracted attention due to its role in water-gas shift, selective oxidation of hydrocarbons and water splitting. In this work, from a well-defined oxygen covered Ag(110) surface with O-(2 × 1) reconstruction, we prepared a fully hydroxylated surface phase in equilibrium with water and oxygen in the gas phase under near ambient conditions.

X-ray Photoelectron Fingerprints of High-Valence Ruthenium-Oxo Complexes along the Oxidation Reaction Pathway in an Aqueous Environment.

Recent advances in -synchrotron-based X-ray techniques are making it possible to address fundamental questions related to complex proton-coupled electron transfer reactions, for instance, the electrocatalytic water splitting process. However, it is still a grand challenge to assess the ability of the different techniques to characterize the relevant intermediates, with minimal interference on the reaction mechanism. To this end, we have developed a novel methodology employing X-ray photoelectron spectroscopy (XPS) in connection with the liquid-jet approach to probe the electrochemical properties of a model electrocatalyst, [Ru(bpy)(py)(OH)], in an aqueous environment.

Are multiple oxygen species selective in ethylene epoxidation on silver?

The nature of the oxygen species active in ethylene epoxidation is a long-standing question. While the structure of the oxygen species that participates in total oxidation (nucleophilic oxygen) is known the atomic structure of the selective species (electrophilic oxygen) is still debated. Here, we use both and UHV X-ray Photoelectron Spectroscopy (XPS) to study the interaction of oxygen with a silver surface.

Thermodynamic and spectroscopic properties of oxygen on silver under an oxygen atmosphere.

We report on a combined density functional theory and the experimental study of the O1s binding energies and X-ray Absorption Near Edge Structure (XANES) of a variety of oxygen species on Ag(111) and Ag(110) surfaces. Our theoretical spectra agree with our measured results for known structures, including the p(N× 1) reconstruction of the Ag(110) surface and the p(4 × 4) reconstruction of the Ag(111) surface. Combining the O1s binding energy and XANES spectra yields unique spectroscopic fingerprints, allowing us to show that unreconstructed atomic oxygen is likely not present on either surface under equilibrium conditions at oxygen chemical potentials typical for ethylene epoxidation.

Adsorbate induced vacancy formation on silver surfaces.

The energy required to form and remove vacancies on metal surfaces mediates the rate of mass transport during a wide range of processes. These energies are known to be sensitive to environmental conditions. Here, we use electronic structure density functional theory calculations to show that the surface vacancy formation energy of silver changes markedly in the presence of adsorbed and dissolved oxygen.

A near ambient pressure XPS study of Au oxidation.

The surface of a gold foil under ozone oxidation was examined by near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) and scanning electron microscopy (SEM). Our in situ observations show that a surface oxide phase is formed during the exposure to ozone; however this phase decomposes under vacuum and even in the presence of ozone at temperatures higher than 300 °C. Assuming that an oxide overlayer completely covers the Au surface, the thickness of the oxide phase was estimated to be between 0.

The silver-oxygen system in catalysis: new insights by near ambient pressure X-ray photoelectron spectroscopy.

We addressed the interaction of oxygen with silver by synchrotron based near ambient pressure X-ray photoelectron spectroscopy at temperatures relevant for industrial oxidation reactions performed with silver catalysts. For silver single crystals, polycrystalline foils and powders in equilibrium with gas phase O(2), we observed the dynamics of the formation of five different atomic oxygen species with relative abundances depending on the temperature and time. Correlation of their formation kinetics with spectroscopic features and thermal stability indicates that these are distinct species with different electronic structures, which might relate to the different roles of silver in oxidation reactions.

Structure and morphology of spinel MFe2O4 (M=Fe, Co, Ni) nanoparticles chemically synthesized from heterometallic complexes.

We synthesized magnetic spinel ferrites from trimetallic single-source precursors. Fe(II), Co(II), and Ni(II) ferrite nanoparticles in the range of 9-25 nm were synthesized by solvothermal decomposition of trimetallic acetate complex precursors in benzyl ether in the presence of oleic acid and oleylamine, using 1,2-dodecanediol as the reducing agent. For comparison, spinel ferrite nanoparticles were synthesized by stoichiometric mixtures of metal acetate or acetylacetonate salts.

Chemical synthesis and structural characterization of highly disordered N colloidal nanoparticles.

This work focuses on synthetic methods to produce monodisperse Ni colloidal nanoparticles (NPs), in the 4-16 nm size range, and their structural characterization. Narrow size distribution nanoparticles were obtained by high-temperature reduction of a nickel salt and the production of tunable sizes of the Ni NPs was improved compared to other methods previously described. The as-synthesized nanoparticles exhibited spherical shape and highly disordered structure, as it could be assigned by X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM).

Growth aspects of photochemically synthesized silver triangular nanoplates.

Aspects of the growth mechanism of silver triangular nanoplates by photochemical synthesis were addressed by detailed characterization using ultraviolet-visible spectroscopy, electron microscopies, and atomic force microscopy. The quantitative characterization of their size and thickness during the reaction showed that both increase with time as well as the aspect ratio. Samples irradiated by different wavelengths showed that the size of the nanoplates can be controlled by the incident wavelength and it is responsible for the increase of the aspect ratio, but the thickness seems to be determined by the conditions of the initial seeds.