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The adsorption and adhesion energies of vapor-deposited Ag on rutile TiO2(100) films have been measured using single-crystal adsorption calorimetry and He+ low-energy ion scattering spectroscopy. A...

Solvent/metal adhesion energies are crucial for understanding solvent effects on adsorption energies, which are, in turn, central to understanding liquid-phase catalysis, electrocatalysis, and many...

The morphology, interfacial bonding energetics, and charge transfer of Ni clusters and nanoparticles on slightly reduced CeO2-x(111) surfaces at 100-300 K have been studied using single-crystal adsorption calorimetry (SCAC), low-energy ion scattering spectroscopy (LEIS), X-ray photoelectron spectroscopy (XPS), low-energy electron diffraction (LEED), and density functional theory (DFT). The initial heat of adsorption of Ni vapor decreased with the extent of pre-reduction (x) of CeO2-x(111), showing that stoichiometric ceria adsorbs Ni more strongly than oxygen vacancies. On CeO1.95(111) at 300 K, the heat dropped quickly with coverage in the first 0.1 ML, attributed to nucleation of Ni clusters on stoichiometric steps, followed by the Ni particles spreading onto less favorable terrace sites. At 100 K, the clusters nucleate on terraces due to slower diffusion. Adsorbed Ni monomers are in the +2 oxidation state, and they bind more strongly by ∼45 kJ/mol to step sites than terraces. The measured heat of adsorption versus average particle size on terraces is favorably compared to DFT calculations. The Ce 3d XPS line shape showed an increase in Ce3+/Ce4+ ratio with Ni coverage, providing the number of electrons donated to ceria per Ni atom. The charge transferred per Ni is initially large but strongly decreases with increasing cluster size for both experiments and DFT, and it shows large differences between clusters at steps versus terraces. This charge is localized on the interfacial Ni and Ce atoms in their atomic layers closest to the interface. This knowledge is crucial to understanding the nature of the active sites on the surface of Ni/CeO2 catalysts, for which metal-oxide interactions play a very important role in the activation of O-H and C-H bonds. The changes in these interactions with Ni particle size (metal loading) and the extent of reduction of ceria help to explain how previously reported catalytic activity and selectivity change with these same structural details. Fil: Mao, Zhongtian. University of Washington; Estados Unidos Fil: Lustemberg, Pablo German. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; Argentina. Consejo Superior de Investigaciones Científicas. Instituto de Catálisis y Petroleoquímica; España Fil: Rumptz, John R.. University of Washington; Estados Unidos Fil: Ganduglia Pirovano, Maria Veronica. Consejo Superior de Investigaciones Científicas. Instituto de Catálisis y Petroleoquímica; España Fil: Campbell, Charles T.. University of Washington; Estados Unidos

The morphology, interfacial bonding energetics and charge transfer of Ni clusters and nanoparticles on slightly-reduced CeO2-x (111) surfaces at 100 to 300 K have been studied using single crystal adsorption calorimetry (SCAC), low-energy ion scattering spectroscopy (LEIS), X-ray photoelectron spectroscopy (XPS), low energy electron diffraction (LEED) and density functional theory (DFT). The initial heat of adsorption of Ni vapor decreased with the extent of pre-reduction (x) of the CeO2-x (111), showing that stoichiometric ceria adsorbs Ni more strongly than oxygen vacancies. On CeO1.95 (111) at 300 K, the heat dropped quickly with coverage in the first 0.1 ML, attributed to nucleation of Ni clusters on stoichiometric steps, followed by the Ni particles spreading onto less favorable terrace sites. At 100 K, the clusters nucleate on terraces dueto slower diffusion. Adsorbed Ni monomers are in the +2 oxidation state, and they bind by ~45 kJ/mol more strongly to step sites than terraces. The measured heat of adsorption versus average particle size on terraces is favorably compared to DFT calculations. The Ce 3d XPS lineshapeshowed an increase in Ce3+/Ce4+ ratio with Ni coverage, providing the number of electrons donated to the ceria per Ni atom. The charge transferred per Ni is initially large but strongly decreases with increasing cluster size for both experiments and DFT, and shows large differences between clusters at steps versus terraces. This charge is localized on the interfacial Ni and Ce atoms in their atomic layers closest to the interface. This knowledge is crucial to understanding the nature of the active sites on the surface of Ni-CeO2 catalysts for which metal-oxide interactions play a very important role in the activation of O−H and C−H bonds. The changes in these interactions with Ni particle size (metal loading) and the extent of reduction of the ceria help to explain how previously reported catalytic activity and selectivity change with these same structural details.

Solar thermochemical ammonia (NH3) synthesis (STAS) is a potential route to produce NH3 from air, water, and concentrated sunlight. This process involves the chemical looping of an active redox pair that cycles between a metal nitride and its complementary metal oxide to yield NH3. To identify promising candidates for STAS cycles, we performed a high-throughput thermodynamic screening of 1,148 metal nitride/metal oxide pairs. This data-driven screening was based on Gibbs energies of crystalline metal oxides and nitrides at elevated temperatures, G(T), calculated using a recently introduced statistically learned descriptor and 0 K DFT formation energies tabulated in the Materials Project database. Using these predicted G(T) values, we assessed the viability of each of the STAS reactions—hydrolysis of the metal nitride, reduction of the metal oxide, and nitrogen fixation to reform the metal nitride—and analyzed a revised cycle that directly converts between metal oxides and nitrides, which alters the thermo...

The Gibbs energy, G, determines the equilibrium conditions of chemical reactions and materials stability. Despite this fundamental and ubiquitous role, G has been tabulated for only a small fraction of known inorganic compounds, impeding a comprehensive perspective on the effects of temperature and composition on materials stability and synthesizability. Here, we use the SISSO (sure independence screening and sparsifying operator) approach to identify a simple and accurate descriptor to predict G for stoichiometric inorganic compounds with ~50 meV atom−1 (~1 kcal mol−1) resolution, and with minimal computational cost, for temperatures ranging from 300–1800 K. We then apply this descriptor to ~30,000 known materials curated from the Inorganic Crystal Structure Database (ICSD). Using the resulting predicted thermochemical data, we generate thousands of temperature-dependent phase diagrams to provide insights into the effects of temperature and composition on materials synthesizability and stability and to establish the temperature-dependent scale of metastability for inorganic compounds., Materials databases currently neglect the temperature effect on compound thermodynamics. Here the authors introduce a Gibbs energy descriptor enabling the high-throughput prediction of temperature-dependent thermodynamics across a wide range of compositions and temperatures for inorganic solids.