Borophene units split water

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.