Boron in Functional Materials: from clusters and catalytic surfaces to ultra-hard alloys
DIPC Seminars
- Speaker
-
Prof. Anastassia Alexandrova, Department of Chemistry and Biochemistry, University of California, Los Angeles (U.C.L.A.) and California NanoSystems Institute
- When
-
2016/12/15
13:00 - Place
- Donostia International Physics Center
- Add to calendar
-
iCal
**Abstract:**
This talk aims to convince you that metal-boron bonds are most unusual and
versatile that the Periodic Table has to offer. Boron being a metalloid, can
be covalent and metallic, cationic, anionic, and neutral, and flux from one
face to another, when bound to metals in equilibrium and during vibrational
motion. As a result, many exciting properties arise. I will show how boration
can promote selectivity of metal surface catalysts for Fischer-Tropsch
synthesis,1 and Pt cluster-based catalyst for dehydrogenation.2,3 This was
first predicted by theory, on the basis of understanding the chemical bonding
in these surfaces and clusters, and then realized experimentally. Metal-boron
bonding also explains the hardness of recently discovered ultra-hard borides.4
The materials are highly valuable, because they free of these limitations of
the hardest materials known, diamond and cubic boron nitride, such as high
price and complications with processing. However, as we will show, the
previously proposed mechanism of their hardness was incomplete. The electronic
structure insight shows that M-B bonds and their promiscuous nature explain
such properties as anisotropic response to stress in WB,5 and the mechanism of
mixed valency in the topological Kondo insulator, SmB6, (which has been an
enigma since the 60s).6 Finally, our pursuit led us to find a new class of
possible 2D materials, which are metallic and in some cases magnetic.7 This is
a theory talk, but the parallel experimental effort will be presented too.
** **
**References:**
1\. Nandula, Trinh, Saeys, Alexandrova, **2015** , _Angew Chem, 54,_ 5312\.
2\. Dadras, Jimenez-Izal, Alexandrova, **2015** , _ACS Catal_., _5_ ,
5719-5727 ** __**
3\. Ha, Baxer, Anderson, Alexandrova, **2016** , in preparation.
4\. Cumberland, R. W.; Weinberger, M. B.; Gilman, J. J.; Clark, S. M.;
Tolbert, S. H.; Kaner, R. B. _J. Am. Chem. Soc._ **2005** , _127_ , 7264-7265.
Chung, H.-Y.; Weinberger, M. B.; Levine, J. B.; Kavner, A.; Yang, J.-M.;
Tolbert, S. H.; Kaner, R. B. _Science_ , **2007** , _316_ , 436-439.
5\. Robinson, Tolber, Kaner, Alexandrova, **2016** , in preparation.
6\. Robinson, Zhang, McQeen, Bowen, Alexandrova, **2016** , under review in
_PNAS_.
7\. Jimenez-Izal, Saeys, Alexandrova, **2016** , _JPC C, 120,_ DOI:
10.1021/acs.jpca.6b07612 __