Operando analysis of water transport in zero-gap CO2 electrolysis cells

Abstract

The movement of water in zero-gap CO₂ electrolysis cells from the anode side to the cathode side may potentially hamper CO₂ transport to the reduction catalyst, ultimately resulting in reduced CO production. To help prevent this, it is desirable to understand where and how water accumulates. Dynamic water transport in zero-gap CO₂ electrolysis cells was visualized by both visible light and X-ray operando imaging. The water breakthrough to the cathode gas channel was visualized by visible light camera observation, while the water seepage through the membrane-electrode assembly was visualized by X-ray radiography. Each frame from the X-ray radiography video was converted to a spatial map of the liquid saturation, and the consecutive frames were used to calculate the liquid flux from the anode to the cathode. This quantitative analysis provides insight into the locations of water accumulation, which tended to occur under the ribs. The flux data showed that, when the water accumulated in the cathode to a certain extent, breakthrough to the cathode flow channel became significant, and water migration from the cathode parts under the ribs to that facing the flow channel also proceeded.