Periodic density functional theory (DFT) calculations and microkinetic modeling are used to investigate the electrochemical oxidation of H2 fuel on the (001) surface of Sr2Fe1.5Mo0.5O6 (SFMO) perovskite under anodic solid oxide fuel cell conditions. Three surface models with different Fe/Mo ratios in the topmost layer-identified by ab initio thermodynamic analysis-are used to investigate the H2 oxidation mechanism. A microkinetic analysis that considers the effects of anode bias potential suggests that a higher Mo concentration in the surface increases the activity of the surface toward H2 oxidation. At operating voltage and anodic SOFC conditions, the model predicts that water desorption is rate-controlling and that stabilizing the oxygen vacancy structure increases the overall rate for H2 oxidation. Although we find that Mo plays a crucial role in improving catalytic activity of SFMO, under fuel cell operating conditions, the Mo content in the surface layer tends to be very low. On the basis of these results and in agreement with previous experimental observations, a strategy for improving the overall electrochemical performance of SFMO is increasing the Mo content or adding small amounts of an active transition metal, such as Ni, to the surface to lower the oxygen vacancy formation energy of the SFMO surface.

It is shown that the effect of water on the bonding characteristics of transition metal surfaces with adsorbates is short-ranged. As a result, adsorption energies in water can be evaluated by a combination of plane-wave density functional theory calculations in vacuum and properly chosen cluster model calculations with and without an implicit solvation model. The scheme is demonstrated for a model C−C cleavage reaction on Pt (111) and for predicting CO frequency shifts on Pd and Pt due to water. We conclude that these shifts originate from water−metal interactions and can be explained by changes in π back-donation. Overall, the results demonstrate that the proposed methodology represents a highly efficient computational approach for approximating the effect of solvents on elementary reaction steps occurring at solid−liquid interfaces of heterogeneous catalysts.

The transport of intercalated Li cations in oxide materials comprises two aspects, ion diffusion and migration of an associated small polaron. We examined computationally these two aspects of Li transport in vanadium pentoxide (V 2 O 5 ) cathode material in a consistent fashion, using a DFT+U approach. Exploring various migration scenarios at low Li concentrations, we determined barriers of ∼0.3 eV, mostly due to polaron migration. In consequence, intercalating Li atoms, at low concentrations, migrate in the interlayer region of V 2 O 5 as quasi-particles where Li cations remain closely associated with their valence electrons, where a small polaron structure forms around the reduced vanadium center.

Mechanisms and properties of the electron transport at the V2O5 cathode of Li-ion batteries were studied by means of first-principles computations.

We utilized first-principles plane-wave calculations to obtain insight into the role of Sn-doping on the behavior of Li intercalation in V2O5 cathode materials used in Li-ion batteries. Density functional theory (DFT+U) calculations were carried out to study microscopic structures and electronic structures of a Sn-doped V2O5 system. We find that the bonding interaction between Sn and the V2O5 lattice displays mixed ionic/covalent character in which Sn donates two of its four valence electrons to the nearby V centers and shares the other two valence electrons with the surrounding lattice. The extra electrons originated from Sn insertion increase the number of charge carriers which could improve electronic conductivity of the material. In addition, Sn insertion induces structural distortion in the V2O5 lattice which in turn affects thermodynamic and kinetic properties of Li intercalation. The calculated insertion energies and diffusion barriers describe how Li intercalates into the V2O5 structure in the presence of Sn. Although the inserted Sn atom may block and trap Li ion, most diffusion paths exhibit lower lying energy levels than those in the pure V2O5, suggesting that Sn-doping facilitates Li intercalation in V2O5-based cathode materials.

The effects of different exchanging ions including Ag, Cu, and Sn on enhancing the photocatalytic activity of KNbTeO6 are investigated by means of experiments and calculations.

Formation of native point defects in semiconductor and their behaviors play a crucial role in material properties. Although native defects of V2O5 include vacancies, self-interstitials, and antisites, only oxygen vacancy...

Because of the interesting activities and relatively high stability, Bi2WO6 photocatalyst has been widely investigated. Several strategies have been proven effective in improving its performance. Here, we investigate the enhancement...