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.

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), Xray 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 due to 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 lineshape showed an increase in Ce 3+ /Ce 4+ 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.

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 other technologies such as adsorption-based separations and chemical sensors. Differences in reactant adsorption energies in different solvents are dominated by differences in their solvent/metal adhesion energies. Here, the adhesion energies of five liquid solvents to clean Pt(111) and Ni(111) surfaces have been estimated using ultrahigh vacuum calorimetric measurements of heats of adsorption versus coverage integrated from zero coverage up to thick (bulk-like) multilayer solid films. The adhesion energies are found to vary from 0.15 to 0.60 J/m2, increasing in the trend CH3OH < HCOOH < H2O < benzene ≈ phenol. This trend indicates that solvents with higher heats of adsorption per unit area in the first adsorbed layer have higher adhesion energies to a given metal surface. The adhesion energies to Ni(111) are generally larger than to Pt(111) (on average by 0.09 J/m2). This is due to the 24% higher number of metal atoms per unit area on Ni(111) than on Pt(111) and, with oxygen-containing solvents, the greater oxophilicity of Ni compared to that of Pt.

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 thermodynamics of the STAS cycle. For all 1148 redox pairs analyzed and each of the STAS-relevant reactions, we implemented a Gibbs energy minimization scheme to predict the equilibrium composition and yields of the STAS cycle, which reveals new active materials based on B, V, Fe, and Ce that warrant further investigation for their potential to mediate the STAS cycle. This work details a high-throughput approach to assessing the relevant temperature-dependent thermodynamics of thermochemical redox processes that leverages the wealth of publicly available temperature-independent thermodynamic data calculated using DFT. This approach is readily adaptable to discovering optimal materials for targeted thermochemical applications and enabling the predictive synthesis of new compounds using thermally controlled solid-state reactions.

Interest in the use of carbon supports for late transition metal nanoparticle catalysts has expanded rapidly due to the increasing importance of electrocatalysts for clean energy and environmental technologies and the use and storage of renewable electricity. Compared to oxide supports, almost nothing is known about the effect of metal nanoparticle size on the energies of the metal atoms within carbon-supported nanoparticles, yet these energies are crucial for understanding their surface reactivity and sintering kinetics. Here, the growth morphology and adsorption energetics of vapor-deposited Ag onto clean graphene/Ni(111) surfaces have been studied using a combination of single-crystal adsorption calorimetry (SCAC) and He+ low-energy ion scattering (LEIS). The differential heat of Ag adsorption is 207 kJ/mol for making ∼30 atom Ag particles on graphene terraces at 100 K and 16 kJ/mol higher for making ∼9 atom Ag clusters at defect sites at the same temperature. The heat of adsorption increases rapidly with Ag coverage as 3D Ag nanoparticles nucleate and grow in size, asymptotically reaching within 5 kJ/mol of the bulk Ag sublimation enthalpy (285 kJ/mol) by 2 ML. The heats of adsorption and Ag nanoparticle densities from LEIS (∼1016/m2) were combined to provide the Ag/graphene adhesion energy (E adh = 1.8 J/m2 in the large-particle limit) and the Ag chemical potential (μ) versus effective particle diameter (D). The Ag chemical potential was well-fitted by μ­(D) = (3γv/M – E adh)­(1 + (1.5 nm)/D)­(2V m/D), where γv/M is the surface energy of bulk Ag and V m is its molar volume. The same equation is known to fit similar data for late transition metals on clean surfaces of metal oxide single crystals. The adhesion energy of Ag measured here on graphene falls within the wide range measured for Ag on those oxide surfaces and is almost as large as on the oxide that binds Ag particles most strongly, namely CeO2(111), which is well-known to be very effective at resisting catalyst deactivation by metal sintering. These results imply that carbon supports will be effective at resisting sintering and that Ag particles smaller than 6 nm on graphene will bind small adsorbed reaction intermediates more weakly than supports with weaker adhesion to Ag, like MgO(100).