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A facile and universal route for synthesizing transition metal borides has been developed by reaction of boron triiodide (BI 3 ) with elemental transition metals. This method employs relatively low synthesis temperatures to afford single-phase samples of various binary and ternary metal borides, such as Fe 2 B, Co 2 B, Ni 3 B, TiB 2 , VB 2 , CrB 2 , and Ni 2 CoB. This synthesis protocol can be utilized for the topotactic transformation of metal shapes into their respective borides, as exemplified by transformation of Ni foam to Ni 3 B foam. In situ powder X-ray diffraction studies of the Ni–BI 3 system showed that the crystalline nickel borides, Ni 4 B 3 and Ni 2 B, start to form at temperatures as low as 700 K and 877 K, respectively, which is significantly lower than the typical synthesis temperatures required to produce these borides. Ni 3 B synthesized by this method was tested as a supporting material for oxygen evolution reaction (OER) in acidic media. Composite electrocatalysts of IrO 2 /Ni 3 B with only 50% of IrO 2 exhibit current densities and stability similar to pure IrO 2 at mass loadings lower than 0.5 mg cm −2 , indicating Ni 3 B could be a promising supporting material for acidic OER.
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Lithium nickel borides: evolution of [NiB] layers driven by Li pressure
Here we show the effect of Li chemical pressure on the structure of layered polymorphs with LiNiB composition: RT -LiNiB (room temperature polymorph) and HT -LiNiB (high temperature polymorph), resulting in stabilization of the novel RT -Li 1+x NiB ( x ∼ 0.17) and HT -Li 1+y NiB ( y ∼ 0.06) phases. Depending on the synthesis temperature and initial Li content, precisely controlled via hydride route synthesis, [NiB] layers undergo structural deformations, allowing for extra Li atoms to be accommodated between the layers. In situ variable temperature synchrotron and time-dependent laboratory powder X-ray diffraction studies suggest Li step-wise deintercalation processes: RT- Li 1+x NiB → RT- LiNiB (high temp.) → LiNi 3 B 1.8 → binary Ni borides and HT -Li 1+y NiB → HT -LiNiB (high temp.) → LiNi 3 B 1.8 → binary Ni borides. Quantum chemistry calculations and solid state 7 Li and 11 B NMR spectroscopy shed light on the complexity of real superstructures of these compounds determined from high resolution synchrotron powder diffraction data.
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- PAR ID:
- 10211044
- Date Published:
- Journal Name:
- Inorganic Chemistry Frontiers
- ISSN:
- 2052-1553
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/D0QI01150A
