Photoemission study of electronic structures of disordered Ni-Pt and Cu-Pt alloys

Thermally Robust Porous Bimetallic (Ni xPt1- x) Alloy Mesocrystals within Carbon Framework: High-Performance Catalysts for Oxygen Reduction and Hydrogenation Reactions

Thermally stable porous bimetallic (Ni _xPt_{1- x}) alloy mesocrystals within a carbon framework are produced via an aerosol-assisted process for high-performance catalysts for the oxygen reduction reaction (ORR) and hydrogenation. The porous Ni _xPt_{1- x} alloy has a robust composite of alloy nanoparticles with an adjustable composition and a porous carbon skeleton. Porous Ni _xPt_{1- x} alloys exhibit high thermal stability, retaining their crystalline structure and morphology at 550 °C for 6 h, as observed in thermal treatment tests under various conditions (time, temperature, and atmosphere). The porous Ni _xPt_{1- x} alloy as a catalyst for the hydrogenation of propylene has high conversion efficiency (>80%) and low activation energy ( E_a < 20 kJ/mol) at ≥80 °C through the suitable control of the element composition and a pore structure. As a catalyst for the ORR, the catalytic activity of the porous Ni _xPt_{1- x} alloy is superior to that of conventional Pt/C (0.115 mA) (0.853 mA/cm_Pt² at 0.9 V/cm_Pt²). This is attributed to the homogeneous alloying of the metal components (Ni and Pt) and the increased accessibility of the reactants to the catalyst, resulting from the unique morphology of the porous Ni _xPt_{1- x} alloy, i.e., hierarchical structure with high porosity.

The quasiparticle band structures of ordered NixPt1-x

The quasiparticle band structures of the ordered L1₂ and L1₀ phases of Ni_xPt_1-x (x = 0.25, 0.5, and 0.75) have been calculated and compared to the band structures obtained using density functional theory. For each alloy, an increase in the curvature of the band structure is generally seen when the quasiparticle correction is made. Non-dispersive regions are shown to include a dispersive component under the quasiparticle correction. The quasiparticle weights are k-dependent and greater towards the Γ point. Non-linear analytical modelling of the quasiparticle correction is shown to be complex.

Cooper minima in the photoemission spectra of solids

Variations of the photoionization cross section of valence states as a function of interatomic distance are studied by means of atomic and solid-state density functional approaches and compared with photoemission data. In contrast to the free atom case, a series of Cooper minima is found for 4d, 5d, and 5f states in Pd, Ag, Au, and U metals. The discovered fundamental phenomenon is of high importance for the correct interpretation of photoemission data.