Catalytic mechanisms of Au₁₁ and Au₁₁-nPt n (n=1-2) clusters: a DFT investigation on the oxidation of CO by O₂

Single atom alloy catalyst for SO3 decomposition: enhancement of platinum catalyst's performance by Ag atom embedding

Recently, single atom alloy catalysts (SAA) have shown improved catalytic activity in numerous catalytic reactions. However, to date, single atom alloy (SAA) catalyst is not available for SO3 decomposition reaction, which is a key reactions in the hydrogen economy. Using state of the art density functional theory, we report a novel single Ag atom alloy Pt catalyst in the sub-nanometer length scale (AgPt9@Al2O3) showing superior catalytic behavior for SO3 decomposition. It was found that alloying the alumina-supported platinum nanocluster with a single Ag atom lowers the activation barrier for S-O bond breaking by more than 50% in comparison with the pristine platinum counterpart. Activation barrier for AgPt9@Al2O3 catalyst is 0.52 eV, which is the lowest of any platinum based catalyst reported so far. At variance with pure Pt10@Al2O3, which tries to detach from the support during decomposition reaction, single atom alloy (SAA) nanocluster AgPt9@Al2O3 enhances binding with support, thus strengthening sintering resistance. Notably, influence of single Ag atom is also observed at larger length scale, i.e., at Pt(111) slab, where single Ag atom substituted surface Ag1Pt(111) shows ∼30% reduction in activation barrier in contrast to a pristine surface. Single Ag atom works in bifunctional mode as it not only reduces the activation barrier, but also simultaneously weakly adsorbs the reaction product SO2, signifying relatively easier desorption and better recyclability. Deeper location of silver d-electrons and lesser electronegativity of silver is responsible for the better performance of single Ag atom alloyed Pt catalyst. We strongly believe that these remarkable results will open new avenues for future designing and fabrication of cost-effective catalysts for SO3 decomposition.

CO oxidation on inverse Ce6O12/Cu(111) catalyst: role of copper-ceria interactions

The surface structures, O₂ adsorption, and CO oxidation reaction properties of Ce₆O₁₂/Cu(111) have been investigated using density functional theory including on-site Coulomb corrections (DFT + U). Results show that the supported ceria nanoparticles would gain electrons from the Cu(111) surface, and the Ce⁴⁺ are reduced to Ce³⁺. In addition, the oxygens at the interface have been largely activated, resulting in much low formation energy of O vacancies. For the CO oxidation reaction, two possible pathways are investigated, CO reacts with the O₂ molecule adsorbed on Ce³⁺ and the lattice O at the interface, respectively. It has been found that CO reacting with the lattice O atom gives a lower reaction barrier than that of adsorbed O₂ on Ce³⁺. These results are important for further understanding of the role of different active sites on the inverse CeO_x/Cu(111) surface structure.

Density Functional Study of Trimetallic AuxPdyPtz (x + y + z = 7) Clusters and Their Interactions with the O2 Molecule

Density functional theory calculations were performed to investigate the structural and energetic properties of trimetallic Au_xPd_yPt_z clusters with x + y + z = 7. The possible stable geometrical configurations with their electronic states are determined. We analyze the chemical order, binding energies, vertical ionization potential, electron affinity, and HOMO-LUMO gaps as a function of the whole concentration range. The affinity of Au_xPd_yPt_z clusters toward one O₂ molecule is also evaluated in terms of the changes in geometry, adsorption energy, and charge transfer.