First Principle Study on Structural, Electronic, Magnetic, and Optical Properties of Co-Doped Middle Size Silver Clusters.

The structural, electronic, magnetic, and optical properties of Co-doped 10-20-atom silver clusters are investigated by GGA/PBE via the density functional theory. The Ag-Co clusters form core-shell structures with a Co atom in the center. Co atom doping modulates electronic properties like energy gap, molecular softness, global hardness, electronegativity, and electrophilicity index. For the optical spectra of the Ag-Co clusters, the energy of their spectra overall exhibits little change with increasing numbers of atoms; the strongest peaks are roughly distributed at 3.5 eV, and the intensity of their spectra overall is strengthened. Raman and vibrational spectra reflect structural changes with Co atom addition. The addition of the Co atom alters magnetic moments of specific Ag-Co clusters, while others remain unchanged.

Understanding the selection of catalytic pathway on graphene-supported nitrogen coordinated Ru-atom by ab initio molecular dynamics simulation.

CONTEXT: In the paper, the ORR/OER on graphene-supported nitrogen coordinated Ru-atom (Ru-N-C) is simulated. We discuss nitrogen coordination influences electronic properties, adsorption energies, and catalytic activity in a single-atom Ru active site. The over potentials on Ru-N-C are 1.12 eV/1.00 eV for ORR/OER. We calculate Gibbs-free energy (ΔG) for every reaction step in ORR/OER process. In order to gain a deeper understanding of the catalytic process on the surface of single atom catalysts, the ab initio molecular dynamics (AIMD) simulations show that Ru-N-C has a structural stability at 300 K and that ORR/OER on Ru-N-C can occur along a typical four-electron process of reaction. AIMD simulations of catalytic processes provide detailed information about atom interactions. METHODS: In this paper, we use density functional theory (DFT) with PBE functional to study the electronic properties and adsorption properties of graphene-supported nitrogen coordinated Ru-atom (Ru-N-C) Gibbs-free energy and Gibbs-free energy for very reaction step. The structural optimization and all the calculations are carried out by Dmol3 package, adopting the PNT basis set and DFT semicore pseudopotential. Ab initio molecular dynamics simulations (AIMD) were run for 10 ps. The canonical (NVT) ensemble, massive GGM thermostat, and a temperature of 300 K are taken into account. The functional of B3LYP and the DNP basis set are chosen for AIMD.

Facile hydrothermal synthesis of layered 1T' MoTe2 nanotubes as robust hydrogen evolution electrocatalysts.

Layered transition metal dichalcogenides (TMDs), such as molybdenum ditelluride (MoTe2), have attracted much attention because of their novel structure-related physicochemical properties. In particular, semi-metallic-phase MoTe2 (1T') is considered as a competitive candidate for low-cost electrocatalysts for water splitting. However, there are few reports on the simple hydrothermal synthesis of MoTe2 nanostructures compared with other layered TMDs. In this study, a facile one-step hydrothermal process was developed for the fabrication of layered MoTe2, in which uniform nanotubes with a few layers of 1T' MoTe2 were fabricated at a lower temperature for the first time. The as-obtained MoTe2 nanotubes were fully characterized using different techniques, which revealed their structure and indicated the presence of layered 1T' nanocrystals. The efficient activity of MoTe2 nanotubes for the electrocatalytic hydrogen evolution reaction (HER) in 0.5 M H2SO4 was demonstrated by the small Tafel slope of 54 mV/dec-1 and endurable ability, which is attributed to the abundant active sites and remarkable conductivity of 1T' MoTe2 with a few-layer feature. This provides a facile method for the design and construction of efficient layered MoTe2 based electrocatalysts.

Self-driven microstructural evolution of Au@Pd core-shell nanoparticles for greatly enhanced catalytic performance during methanol electrooxidation.

The lack of direct insight into the microstructural evolution of catalytic materials under electrochemical polarization has inhibited the development of heterogeneous catalysts. By investigating a typical Au@Pd core-shell nanostructure, the present study discloses the microstructural evolution of heterogeneous catalytic materials during the methanol electrooxidation reaction (MOR). The electrocatalytic activity of the as-prepared Au@Pd_core-shell nanoparticles continuously increased during the first 100 successive voltammetry cycles of the MOR. Microstructural characterization studies revealed that during the MOR, an Au/Pd mixed bimetallic shell was formed by the self-driven microstructural evolution of the Au@Pd_core-shell nanoparticles. Both the experimental and calculation results indicated that the Au/Pd mixed bimetallic shell reduced the binding strength of OH- and CO on the catalyst surface. The exposed Au atoms in the shell region also produced large-scale reactive ˙OH radicals that facilitated the oxidative removal of the adsorbed carbonaceous species from the adjacent Pd active sites.