Electrode behavior of Si and evolution of SiH4 in molten LiCl-KCl-LiH systems

A novel SiH4 production method using molten salt electrochemical process ha s been proposed. In order to examine the possibility of the method, a poten tial-pH(-) diagram was constructed for the Si-H system in a LiCl-KCl eutect ic melt. The electrode behavior of a single crystal Si electrode was invest igated by cyclic voltammetry in molten LiCl-KCl-LiH(5 mol %) systems at 673 K. The result showed that a passivation film was formed on the electrode b y anodic polarization and that further polarization leads to breakdown of t he passivation film. From the IR absorption spectroscopy of the evolved gas , SiH4 production was confirmed. Fluoride ion addition to the melt was foun d to be effective for promoting the SiH4 production. The current efficiency for the SiH4 evolution was improved to about 20 % by using a lower LiH(0.8 mol %) system, which suggests that SiH4 evolution mainly proceeds by the i ndirect reaction of chlorosilanes.