Studies of perfluorocarbon formation on anodes in cryolite melts

Abstract

The aluminium industry is today the primary source of perfluorocarbon (PFC) to the atmosphere. These gases have a lifespan of several thousand years, and a greenhouse warming potential (GWP) 6500-10000 times that of CO2. It is therefore of essential to understand, and reduce, the PFC emissions. Controlled potential electrolysis with gas analysis was utilized to study the PFC production in a laboratory cell during regular electrolysis conditions, and during anode effects. A 3-electrode setup with an Al reference electrode was utilized to monitor the anodic voltage. The combination of Mass Spectrometry (MS) and Fourier Transformed Infrared Spectroscopy (FTIR) was used to characterize the off gas. Traces of CF4 were found in the anode gases at anodic voltages as low as 2.9 V VS the Al reference electrode, confirming that the PFC production can occur unrelated to the anode effect. However C2F6 was only detected during anode effects.