Carbon corrosion in low-temperature CO2 electrolysis systems

Carbon corrosion has been widely documented in electrochemical systems such as fuel cells and water electrolyzers. In these systems, CO2 is neither a reactant or a product, and CO2 produced from carbon corrosion can be directly measured and attributed to the carbon corrosion process. In CO2 electrolysis, the CO2 feed masks the detection of CO2 produced from anodic carbon corrosion, making the quantification of carbon corrosion difficult. Additionally, current CO2 electrolysis systems operate in a different chemical environment than fuel cells and water electrolysis systems, often employing a carbonate-based anolyte. Understanding and quantifying failure modes is critical for the commercialization of CO2 electrolysis, where a durability of multiple years is required. However, at present, many published studies employ carbon-based materials on the anode. These carbon-based anodes may corrode and deteriorate under the oxidative potentials present on the anode under normal CO2 electrolysis operation. Carbon corrosion at the anode may also be convoluted with other common degradation mechanisms, making quantification of specific degradation pathways more challenging. Here, we have developed an ex situ carbon corrosion test for CO2 electrolysis that allows for the quantification of mass loss from carbon corrosion. Using this test, significant carbon corrosion has been quantified at realistic anodic voltages experienced in operating CO2 electrolysis cells. Based on these results, and informed from the past experiences in the development of fuel cell and water electrolysis systems, we provide a perspective on the use of carbon-based materials on the anode of CO2 electrolysis systems. The CO2 utilization community would benefit from rapidly transitioning away from the use of carbon-based materials on the anode of CO2 electrolysis systems. If carbon materials are used on the anode in CO2 electrolysis systems, it is only appropriate for short-term (<100 h) experiments.