(599a) Boron Nanoparticle Synthesis and Application in Hydrogen Generation

Hydrogen is the most abundant element on earth. However, it does not exist naturally in its molecular form and it must be produced from other resources. Water splitting is a potential method to produce hydrogen, but direct thermolysis of water requires temperatures above 2500 K. Chemical water splitting, by reacting water with a metal to produce a metal oxide is an attractive method of splitting water at much lower temperature. Among all inorganic solids, elemental boron is particularly interesting for this approach. Boron has a high gravimetric hydrogen production potential (277 g H₂/kg material), which is even higher than silicon and aluminum (140 and 110 g H₂/kg material, respectively). Few studies of water splitting by reaction with boron have been published, but these have used very high reaction temperatures.  We produced highly pure amorphous boron nanoparticles (BNPs) and facilitated boron hydrolysis at room temperature by addition of alkali metals that can catalyze the reaction.  BNPs were prepared in a single step gas phase process via CO₂ laser-induced pyrolysis of B₂H₆ and SF₆ mixtures. The BNPs are spherical with a primary particle diameter of 10-15 nm, narrow size distribution and specific surface areas exceeding 200 m²/g. In addition to the hydrogen generation process that is the focus of the present effort, these have obvious potential as fuel additives and in related applications that take advantage of the extremely high gravimetric and volumetric heats of combustion of boron.