Ruthenium boride

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Structure of orthorhombic RuB2. Green atoms are Ru, pink - boron OsB2structure.JPG
Structure of orthorhombic RuB2. Green atoms are Ru, pink - boron

Ruthenium borides are compounds of ruthenium and boron. Their most remarkable property is potentially high hardness. Vickers hardness HV = 50 GPa was reported for thin films composed of RuB2 and Ru2B3 phases. [1] This value is significantly higher than those of bulk RuB2 or Ru2B3, but it has to be confirmed independently, as measurements on superhard materials are intrinsically difficult. For example, note that the initial report on extreme hardness of related material rhenium diboride [2] was probably too optimistic. [3]

Structure

Ruthenium diboride was first thought to have a hexagonal structure, [4] as in rhenium diboride, but it was later tentatively determined to possess an orthorhombic structure. [5]

For the crystal structure of RuB2, it was found that the boron atoms were arranged in puckered layers with the "boat" configuration, which formed 2D sheets within a 3D network of metallic bondings of ruthenium atoms. Additionally, such a "boat" configuration was found to be critical in promoting the activity and stability of RuB2 in the hydrogen evolution reaction (HER). [6]

References

  1. ↑ J.V. Rau et al. "Deposition and characterization of superhard biphasic ruthenium boride films" Acta Materialia 57 (2009) 673
  2. ↑ Chung, Hsiu-Ying; et al. (April 20, 2007). "Synthesis of Ultra-Incompressible Superhard Rhenium Diboride at Ambient Pressure". Science. 316 (5823): 436–9. Bibcode:2007Sci...316..436C. doi:10.1126/science.1139322. PMID   17446399. S2CID   10395879.
  3. ↑ J. Qin et al. "Is Rhenium Diboride a Superhard Material?" Adv. Mater. 20 (2008) 4780
  4. ↑ C. P. Kempter and R. J. Fries "Crystallography of the Ru-B and Os-B Systems" J. Chem. Phys. 34, 1994 (1961)
  5. ↑ R. B. Roof, Jr. and C. P. Kempter "New Orthorhombic Phase in the Ru-B and Os-B Systems" J. Chem. Phys. 37, 1473 (1962)
  6. ↑ Chen, Hui; et al. (2020). "Intermetallic borides: structures, synthesis and applications in electrocatalysis". Inorg. Chem. Front. 7: 2248–2264. doi:10.1039/d0qi00146e.
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