Suppressing Hydrogen Evolution by Aqueous Silicon Powder Dispersions Through the Introduction of an Additional Cathodic Reaction

Abstract

Silicon powder reacts with water liberating hydrogen gas that poses an explosion risk.Adding metal ions with a high reduction potential suppresses hydrogen generation. Copper (II) ions are particularly effective in this regard. In their presence the reaction featured three distinct stages. In the initial phase copper is deposited on the silicon surface concomitant with a rapid drop in the solution pH. Most of the hydrogen evolves during a second active stage with the pH showing a slight upward drift. Finally, in the third stage, the silicon surface passivates and hydrogen evolution comes to a halt. A comparison of this method and two other methods previously reported i.e. controlled air oxidation of the silicon powder before slurrying and adding organic corrosion inhibitors, shows that silane surface modification of silicon is the most effective method for suppression of hydrogen evolution while maintaining or even improving silicon reactivity in a typical pyrotechnic composition.

Review of Gasless Pyrotechnic Time Delays

“…This process does, therefore, lengthen the life of more reactive materials, including Al, Zn and Mg [37]. Chemical treatment has also been used to prevent hydrogen evolution form fuels during wet mixing of compositions [49].…”

An assessment of the viability of hydrogen generation from the reaction of silicon powder and sodium hydroxide solution for portable applications

“…The rate of reaction of an untreated silicon powder with water is thus negligible unless some method of removing the oxide layer is employed. The overall reaction of silicon with water has been described in previous work by Tichapondwa et al [18,19] and is represented by Equations (1) and (2).…”