Country for PR: Japan
Contributor: Kyodo News JBN
Wednesday, March 25 2020 - 17:00
WPI-MANA Discovers New Insights into Structure of Layered Hydrogen Borides
TSUKUBA, Japan, Mar. 25, 2020 /Kyodo JBN-AsiaNet/ --

A team at the International Center for Materials Nanoarchitectonics (WPI-MANA), 
a unit of the National Institute for Materials Science (NIMS), has determined 
the structure of a layered hydrogen boride synthesized via a soft chemical 
route. The team found that the structure consists of B-H-B bridging bonds and 
B-H terminal bonds, and the local structure induces macroscopic amorphous 
nature by "geometrical frustration." Since the layered hydrogen boride is 
electrically conductive, the finding points the way toward new applications.


The team determined atomic arrangements in the layered hydrogen boride by using 
pair-distribution functions (that is, the probability of finding two atoms 
separated by a certain distance in the material). It found that the material 
mostly consisted of a corrugated B network decorated with three-center, 
two-electron B-H-B bridging bonds, as well as ordinary two-center, two-electron 
B-H terminal bonds. It was locally ordered but amorphous by diffractometry.

The team accounted for this discrepancy by positing geometrical frustration, 
caused by the positions of terminal B-H bonds located on one of two equivalent 
B atoms in the B-H-B bridging bonds. This geometrical frustration accounts for 
the amorphous state of the layered HB and the team dubbed this structure 
"frustrated hydrogen boride" (f-HB).

Local B-H chemical bonds in f-HB appear to govern its macroscopic structure as 
well as its conductivity upon adsorption of molecules. The material is 
electrically conductive rather than ion-conductive, and its B-H-B bonds are 
cleaved by the adsorption of molecules.

Because f-HB is an electrically conductive solid-state material with local 
functional groups that respond to chemical adsorption, these findings could 
open up unique functionalities of HB materials, such as HB nanosheets as 
potential sensing materials and catalysts.

This research was carried out by Satoshi Tominaka (Senior Researcher, Soft 
Chemistry Group, MANA, NIMS) and his collaborators.

"Geometrical Frustration of B-H Bonds in Layered Hydrogen Borides Accessible by 
Soft Chemistry"
Satoshi Tominaka et al., Chem (February 13, 2020);
DOI: 10.1016/j.chempr.2019.11.006


International Center for Materials Nanoarchitectonics (WPI-MANA), National 
Institute for Materials Science (NIMS)