The greatest promotion for the oxidation of EG was observed on Pd 28 Cu 72 /C (7 times faster), for PG was on Pd 11 Cu 89 /C (12 times), and for G was on Pd 63 Cu 37 /C (14 times). We observe a decrease in density of states near the Fermi level with increasing amount of Cu and a shift of the d-band center away from the Fermi energy. This surface electronic perturbation could be one of the factors affecting the oxidation of the polyalcohols. A second factor could be the bi-functional effect as we also observe an increase in hydroxyl adsorption at lower potentials on all PdCu/C compared to Pd/C. Therefore, we suggest that the combination of both of these effects, electronic and bifunctional, contributes to the promotion of the oxidation of these polyalcohols. Furthermore, the ratio of Cu to Pd appears to play an important role in the oxidation rate.

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Palladium is an efficient monoatomic catalyst for the electrochemical oxidation of polyalcohols in alkaline media, yet the oxidation rate is still slow compared to other smaller molecules. In order to improve the oxidation rate, Ni was mixed with Pd for synthesis of PdNi/C nanoparticles. The oxidation rates of ethylene glycol (EG), propylene glycol (PG), and glycerol (G) on Pd/C were compared to the oxidation rates on Pd16Ni84/C, Pd53Ni47/C, and Pd68Ni32/C. The oxidation rate of PG was enhanced by the presence of Ni as much as 14 times (Pd53Ni47/C). The oxidation rate of EG was enhanced 2.3 times on Pd68Ni32/C, and G was improved 2.9 times on Pd53Ni47/C. A significant shift in d‐band center was also observed (as high as +0.11 eV in Pd53Ni47/C) on each PdNi/C catalyst compared to that of Pd/C due to the presence of Ni. The correlation between increased oxidation rate and shift in d‐band center is indicative of the presence of an electronic effect, which is particularly strong for PG.

For over a century, vibrational spectroscopy has enhanced the study of materials. Yet, assignment of particular molecular motions to vibrational excitations has relied on indirect methods. Here, we demonstrate that applying group theoretical methods to the dynamic pair distribution function analysis of neutron scattering data provides direct access to the individual atomic displacements responsible for these excitations. Applied to the molecule-based frustrated magnet with a potential magnetic valence-bond state, LiZn2Mo3O8, this approach allows direct assignment of the constrained rotational mode of Mo3O13 clusters and internal modes of MoO6 polyhedra. We anticipate that coupling this well known data analysis technique with dynamic pair distribution function analysis will have broad application in connecting structural dynamics to physical properties in a wide range of molecular and solid state systems.

Combining neutron diffraction with pair distribution function analysis, we have uncovered hidden reduced symmetry in the correlated metallic d 1 perovskite, SrVO3. Specifically, we show that both the local and global structures are better described using a GdFeO3 distorted (orthorhombic) model as opposed to the ideal cubic ABO3 perovskite type. Recent reports of imaginary phonon frequencies in the density functional theory (DFT)-calculated phonon dispersion for cubic SrVO3 suggest a possible origin of this observed non-cubicity. Namely, the imaginary frequencies computed could indicate that the cubic crystal structure is unstable at T = 0 K. However, our DFT calculations provide compelling evidence that point defects in the form of oxygen vacancies, and not an observable symmetry breaking associated with calculated imaginary frequencies, primarily result in the observed non-cubicity of SrVO3. These experimental and computational results are broadly impactful because they reach into the thin-film and theoretical communities who have shown that SrVO3 is a technologically viable transparent conducting oxide material and have used SrVO3 to develop theoretical methods, respectively.

Emphanisis, or the appearance out of nothing, has been used to describe the phenomena of spontaneous atom off-centering and dipole formation at elevated temperatures in lead chalcogenides. Here, we provide spectroscopic evidence of spontaneous formation of metal-metal bonds above T ~ 50 K in the layered metal KNi2Se2. These bonds form zig-zag chains that lower the local symmetry from tetragonal to monoclinic. Energy-resolved pair distribution function measurements exclude a pure phonon origin of our observations, and instead imply the existence of extra, slowly fluctuating, Ni-Ni bonds above T = 50 K. Density functional theory calculations support this lower symmetry configuration as an instability of tetragonal KNi2Se2. We thus demonstrate that the phenomena of emphansis is not limited to local electric dipole formation, but can also be driven by the formation of metal-metal bonds.

Ba2CaMoO6 was synthesized by solid state method. The crystal structure adopts cubic Fm-3m space group at room temperature with lattice parameters of 8.378231(5) Å. Upon cooling, Ba2CaMoO6 was determined to have a structural phase transition to tetragonal I4/m (a=5.905763(6) Å and c=8.38817(1) Å) around 200 K. The phase transition was probed structurally by synchrotron and neutron diffraction and thermodynamically by specific heat and differential scanning calorimetry measurement. This structural phase transition will deepens our understanding of the perovskite family especially the formation of perovskites that break corner sharing networks.

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