The Influence of a Changing Local Environment during Photoinduced CO Dissociation.

Though largely influencing the efficiency of a reaction, the molecular-scale details of the local environment of the reactants are experimentally inaccessible hindering an in-depth understanding of a catalyst's reactivity, a prerequisite to maximizing its efficiency. We introduce a method to follow individual molecules and their largely changing environment during a photochemical reaction. The method is illustrated for a rate-limiting step in a photolytic reaction, the dissociation of CO on two catalytically relevant surfaces, Ag(100) and Cu(111).

Development and Assessment of a Criterion for the Application of Brønsted-Evans-Polanyi Relations for Dissociation Catalytic Reactions at Surfaces.

We propose and assess a criterion for the application of Brønsted-Evans-Polanyi (BEP) relations for dissociation reactions at surfaces. A theory-to-theory comparison with density functional theory calculations is presented on different reactions, metal catalysts, and surface terminations. In particular, the activation energies of CH, CO, and -COOH dissociation reactions on (100), (110), (111), and (211) surfaces of Ni, Cu, Rh, Pd, Ag, and Pt are considered.

A topological model for predicting adsorption energies of polycyclic aromatic hydrocarbons on late-transition metal surfaces.

We introduce and validate by first-principles calculations an analogy between metal coordination chemistry and the adsorption of polycyclic aromatic hydrocarbons (PAHs) at metal surfaces for the derivation of a model for predicting the PAH adsorption energies. We correlate the binding of PAH on the metal surface with the coordination between metal atom and the ligands in the metal complex, where the formation enthalpy of metal complexes is mainly determined by the strength of a single metal-ligand (M-L) bond and by the number of the M-L bonds. This analogy allows estimation of the adsorption energies only on the basis of the structure of the PAHs and of their adsorption configurations.

First-Principles Simulation of Raman Spectra of Adsorbates on Metal Surfaces.

A general method is proposed to simulate the Raman spectra of adsorbates on metal surfaces. This method is based on an electrostatic-corrected cluster model with additional charges to compensate the loss of coordination of metal atoms, and an external field added to simulate the surface dipole and to reproduce the charge distribution obtained from periodic calculations. As a result, it is possible to couple the phonon calculation with the Raman tensors computed by this corrected cluster model to simulate the Raman spectra of the adsorbates on metal surfaces.

Theoretical studies of the work functions of Pd-based bimetallic surfaces.

Work functions of Pd-based bimetallic surfaces, including mainly M/Pd(111), Pd/M, and Pd/M/Pd(111) (M = 4d transition metals, Cu, Au, and Pt), are studied using density functional theory. We find that the work function of these bimetallic surfaces is significantly different from that of parent metals. Careful analysis based on Bader charges and electron density difference indicates that the variation of the work function in bimetallic surfaces can be mainly attributed to two factors: (1) charge transfer between the two different metals as a result of their different intrinsic electronegativity, and (2) the charge redistribution induced by chemical bonding between the top two layers.