Enduring CO Electrolysis with Ampere-Level Reaction Rates Using Nickel-Doped Iridium Catalysts

CO₂/CO electrolysis offers a scalable pathway for electrosynthesis of multicarbon fuels and chemicals. However, current systems face challenges such as low energy and carbon efficiencies when operated at industrially relevant reaction rates. Our preliminary analysis revealed that the combination of high reaction rates and product crossover-induced pH reduction accelerates anode dissolution, leading to cathode poisoning and, ultimately, performance degradation. Here, we report a strategy to mitigate these challenges by dispersing a low concentration of nickel in an iridium oxide host to promote the stability of iridium species while inhibiting the oxidation of nickel sites. We synthesize a low-valence-nickel in iridium oxide anode material that exhibits high activity and stability for oxygen evolution, while remaining inactive for the oxidation of liquid products migrating from the cathode. In situ soft X-ray photoemission spectroscopy reveals the presence of active sites comprising Ni²⁺ and Ir⁴⁺ species. By incorporating this catalyst into an membrane electrode assembly setup, we achieve CO electroreduction on copper with a full-cell energy efficiency of 32% and a carbon efficiency of 73% at 1000 mA per square centimeter, alongside sustained stability over 1000 h of continuous operation.