Degradation of stainless steel anode catalyst in zero-gap CO2 electrolysis

To date, low temperature CO 2 electrolyzers commonly employ Ir-based catalysts on the anode side. However, Ir is expensive and classified as critical raw material. Thereby, it significantly influences the electrolyzer cost and poses supply chain risks. This study assesses the applicability of stainless steel electrodes as a low-cost alternative to Ir as oxygen evolution reaction catalyst in zero-gap CO 2 electrolysis. Cells with stainless steel electrodes show only 0.25 V higher cell voltage compared to IrO 2 -based cells and significantly higher stability compared to Ni-based cells at an application-relevant current density of 300 mA cm −2 . However, 100 h measurements at 300 mA cm −2 , reveal higher cell voltage degradation (6 mV h −1 vs. 3 mV h −1 ) and a more rapid decrease in faradaic efficiency towards CO. Leaching of Cr and subsequent migration to the cathode is identified as the main cause for the performance degradation. Even though stainless steel does not reach the performance and stability of IrO 2 yet, it could become a low-cost alternative to Ir after further optimization.