Volume 95 Issue 30 | p. 8 | Concentrates
Issue Date: July 24, 2017

Borophene units split water

Graphenelike groupings of boron atoms in molybdenum diboride actively catalyze hydrogen evolution reaction
Department: Science & Technology
Keywords: Hydrogen power, water splitting, catalyst, hydrogen, hydrogen evolution
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Alpha-MoB2, an active water-splitting catalyst, consists of 2-D borophene units (yellow) inserted into a metallic 3-D molybdenum framework (blue). (Mo–Mo bonds not shown in full model.).
Credit: J. Am. Chem. Soc.
These three models show the structure of the alpha-phase of MoB2.
 
Alpha-MoB2, an active water-splitting catalyst, consists of 2-D borophene units (yellow) inserted into a metallic 3-D molybdenum framework (blue). (Mo–Mo bonds not shown in full model.).
Credit: J. Am. Chem. Soc.

A molybdenum-boron material functions as a highly active catalyst for the hydrogen evolution reaction, one of the key steps in liberating hydrogen from water (J. Am. Chem. Soc. 2017, DOI: 10.1021/jacs.7b06337). The promise of a practically limitless supply of clean-burning hydrogen fuel from water spurs scientists to find catalysts that split water into hydrogen and oxygen. Platinum works well, but it’s expensive. MoS2 is a low-cost substitute, but it tends to work best at current densities such as 10 mA/cm2 that are too low for large-scale industrial applications. Tewodros Asefa of Rutgers University, Xiaoxin Zou of Jilin University, and coworkers have come up with a precious-metal-free, high-performing alternative: the α phase of MoB2. The material consists of two-dimensional graphenelike boron structures—borophene units—inserted into a metallic 3-D molybdenum framework. The team reports that α-MoB2 outperforms MoS2 and even outperforms Pt-C reference catalysts, readily delivering current densities on the order of 1,000 mA/cm2. The team attributes α-MoB2’s catalytic prowess to its high electronic conductivity, high density of catalytic sites, and good mass-transport properties.

 
Chemical & Engineering News
ISSN 0009-2347
Copyright © American Chemical Society

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