We report an air and water stable electride Y5Si3 and its catalytic activity for direct ammonia synthesis. It crystallizes in the Mn5Si3-type structure and confines 0.79/f.u. anionic electrons in the quasi-one-dimensional holes. These anionic electrons strongly hybridize with yttrium 4d electrons, giving rise to improved chemical stability. The ammonia synthesis rate using Ru(7.8 wt %)-loaded Y5Si3 was as high as 1.9 mmol/g/h under 0.1 MPa and at 400 °C with activation energy of ∼50 kJ/mol. Its strong electron-donating ability to Ru metal of Y5Si3 is considered to enhance nitrogen dissociation and reduce the activation energy of ammonia synthesis reaction. Catalytic activity was not suppressed even after Y5Si3, once dipped into water, was used as the catalyst promoter. These findings provide novel insights into the design of simple catalysts for ammonia synthesis.

Electrides are ionic crystals in which the anionic electrons are confined to interstitial subnanometer-sized spaces. At present, the reported electrides only consist of main-group elements. Here, we report a layeredstructure transition-metal hypocarbide electride, Y 2 C, with quasi-two-dimensional (quasi-2D) anionic electrons confined in the interlayer space. Physical properties measurements reveal polycrystalline Y 2 C exhibits semimetallic behavior, and paramagnetism with an effective magnetic moment of ∼0.6 μ B / Y, because of the existence of localized d-electrons. Photoelectron spectroscopy measurements illustrate the work function of polycrystalline Y 2 C is 2.9 eV, lower than Y metal, revealing the loosely bound nature of the anionic electrons. Density functional theory calculations indicate the density of states at the Fermi level originates from the states at interstitial sites and the Y 4d-orbitals, supporting the confinement of anionic electrons within the interlayer space. These results demonstrate that Y 2 C is a quasi-2D electride in term of [Y 2 C] 1.8+ •1.8e − , and the coexistence of the anionic electrons and the Y 4d-electrons leads to the semimetallic behavior.

This work reports on the bulk properties of the quaternary Heusler alloy Co 2 Mn 1−x Fe x Si with the Fe concentration x =. All samples, which were prepared by arc melting, exhibit L2 1 long range order over the complete range of Fe concentration. Structural and magnetic properties of Co 2 Mn 1−x Fe x Si Heusler alloys were investigated by means of X-ray diffraction, high and low temperature magnetometry, Mößbauer spectroscopy, and differential scanning calorimetry. The electronic structure was explored by means of high energy photo emission spectroscopy at about 8 keV photon energy. This ensures true bulk sensitivity of the measurements. The magnetization of the Fe doped Heusler alloys is in agreement with the values of the magnetic moments expected for a Slater-Pauling like behavior of half-metallic ferromagnets. The experimental findings are discussed on the hand of self-consistent calculations of the electronic and magnetic structure. To achieve good agreement with experiment, the calculations indicate that on-site electron-electron correlation must be taken into account, even at low Fe concentration. The present investigation focuses on searching for the quaternary compound where the half-metallic behavior is stable against outside influences. Overall, the results suggest that the best candidate may be found at an iron concentration of about 50%.