Role of the Porosity of Carbon Anodes in the Nucleation and Growth of Gas Bubbles

Abstract

During electrolysis, carbon oxide gas is continuously generated in the vicinity of the anode bottom. During their growth, bubbles are fed by the gas by different mechanisms as it was described by the authors earlier. However, the dominating transport mechanism and the principal medium that transfers the gas from the generating sites into the bubbles before detachment are not yet perfectly known. Comparing different bubble growth scenarios, the authors of this paper found that the gas diffusion through a very thin porous layer along the anode bottom can be the most important player in the gas transport. In the present paper, anodes removed from the electrolysis cell under different operating conditions were investigated. The structure of anode bottoms—with and without undergoing electrolysis at the moment of removal—was analyzed to verify whether the earlier theoretical hypothesis about the dominating transport mechanism holds.