GRACIANI ALONSO , Jesús

The stability and structural properties of titanium oxynitrides, TiN1-x Ox, of different compositions are theoretically analyzed by means of first-principles periodic density-functional calculations. We show that at x=0.55-0.6 there is a change in the preferred structure from that of NaCl type to the α-TiO arrangement. For the NaCl-type...

Many transition-metal monoxides formally having an fcc rock-salt structure exhibit a relatively high degree of vacancies, in particular, the most stable structure of stoichiometric titanium monoxide corresponds to a monoclinic phase, α-TiO, showing 15% vacancies. The role of such vacancies on the stability of the solid has been the subject of...

Experimental techniques and DFT calculations have been combined to study and compare the effect of the metal-substrate interaction in Cu/TiO2(110) and Cu/CeOx/TiO2(110) catalysts for the water-gas shift (WGS) reaction. Experiments and theory show that CeOx nanoparticles affect the dispersion of copper on titania, and on the formed copper-ceria...

This work presents a detailed experimental and theoretical study of the oxidation of TiN(001) using a combination of synchrotron-based photoemission and density functional theory (DFT). Experimentally, the adsorption of O2 on TiN(001) was investigated at temperatures between 250 and 450K. At the lowest temperature, there was chemisorption of...

Nanostructured RuOx/TiO2(110) catalysts have a remarkable catalytic activity for CO oxidation at temperatures in the range of 350-375 K. On the other hand, the RuO2(110) surface has no activity. The state-of-the-art DFT calculations indicate that the main reasons for such an impressive improvement in the catalytic activity are: (i) a decrease...

The electronic properties of N-doped rutile TiO2(110) have been investigated using synchrotron-based photoemission and density-functional calculations. The doping via N+2 ion bombardment leads to the implantation of N atoms (∼5% saturation concentration) that coexist with O vacancies. Ti 2p core level spectra show the formation of Ti3+ and a...

The structural and electronic properties of CeOx species supported on the rutile TiO2 110 surface have been examined by means of periodic density-functional calculations that use a generalized gradient approximation functional including a Hubbard-like type correction. Deposition of Ce atoms leads in a first step to Ce3+ ions bound to the...

Ceria‐titania interfaces play a crucial role in different chemical processes but are especially promising for the photocatalytic splitting of water using light in the visible wavelength region when Pt is added to the system. However, the complexity of this hierarchical structure hampers the study of the origin of its outstanding properties. In...

The addition of potassium atoms to Cu(111) and Cu/TiO2(110) surfaces substantially enhances the rate for water dissociation and the production of hydrogen through the water-gas shift reaction (WGS, CO + H2O → H2 + CO2). In the range of temperatures investigated, 550-625 K, Cu/K/TiO2(110) exhibits a WGS activity substantially higher than those...

Inverse oxide/metal catalysts have shown to be excellent systems for studying the role of the oxide and oxide-metal interface in catalytic reactions. These systems can have special structural and catalytic properties due to strong oxide-metal interactions difficult to attain when depositing a metal on a regular oxide support. Oxide phases that...

The adsorption and dissociation of CO2 on TiO2(110), CeOx/TiO2(110) and Pt/CeOx/TiO2(110) surfaces has been examined using Ambient Pressure X-ray Photoelectron Spectroscopy (AP-XPS). The substrates under study exhibited different degrees of complexity which were tested for the binding of the adsorbate and the cleavage of C-O bonds. The surfaces...

Mixed-metal oxides play a very important role in many areas of chemistry, physics, materials science, and geochemistry. Recently, there has been a strong interest in understanding phenomena associated with the deposition of oxide nanoparticles on the surface of a second (host) oxide. Here, scanning tunneling microscopy, photoemission, and...

Potassium deposition on TiO2(110) results in reduction of the substrate and formation of loosely bound potassium species that can move easily on the oxide surface to promote catalytic activity. The results of density functional calculations predict a large adsorption energy (∼3.2 eV) with a small barrier (∼0.25 eV) for diffusion on the oxide...

The immobilization of miniscule quantities of RuO2 (∼0.1%) onto one-dimensional (1D) TiO2 nanorods (NRs) allows H2 evolution from water under visible light irradiation. Rod-like rutile TiO2 structures, exposing preferentially (110) surfaces, are shown to be critical for the deposition of RuO2 to enable photocatalytic activity in the visible...

Capture and recycling of CO2 into valuable chemicals such as alcohols could help mitigate its emissions into the atmosphere. Due to its inert nature, the activation of CO2 is a critical step in improving the overall reaction kinetics during its chemical conversion. Although pure gold is an inert noble metal and cannot catalyze hydrogenation...