Electrodeposition of Silicon with a Liquid Gallium Cathode in Molten Salts

Abstract

Further development of solar power depends largely on the availability of inexpensive solar grade silicon. Electrodeposition is a candidate method to produce high purity silicon at a reasonable cost. A new approach using a liquid gallium cathode was used to study deposition of silicon from molten salt electrolytes containing K2SiF6. Electrochemical studies and electrolysis to deposit silicon from molten eutectic KCl–KF with additions of K2SiF6 were carried out at 650 oC. Silver wire and glassy carbon rod were used as working electrodes, while glassy carbon rod or silver wire were counter electrodes. A silicon plate reference electrode was used. Liquid gallium in a small alumina tube with tungsten lead was the cathode during electrolysis while glassy carbon or silicon was the anode. Silicon was found to deposit inside a liquid gallium cathode during electrolysis. The current efficiency was found to be quite high, and consistently above 80 %.