Highly Efficient CO₂ Electrolysis on Cathodes with Exsolved Alkaline Earth Oxide Nanostructures

The solid oxide CO₂ electrolyzer has the potential to provide storage solutions for intermittent renewable energy sources as well as to reduce greenhouse gas emissions. One of the key challenges remains the poor adsorption and activity toward CO₂ reduction on the electrolyzer cathode at typical operating conditions. Here, we show a novel approach in tailoring a perovskite titanate (La, Sr)TiO_3+δ cathode surface, by the in situ growing of SrO nanoislands from the host material through the control of perovskite nonstoichiometry. These nanoislands provide very enhanced CO₂ adsorption and activation, with stability up to 800 °C, which is shown to be in an intermediate form between carbonate ions and molecular CO₂. The activation of adsorbed CO₂ molecules results from the interaction of exsolved SrO nanoislands and the defected titanate surface as revealed by DFT calculations. These cathode surface modifications result in an exceptionally high direct CO₂ electrolysis performance with current efficiencies near 100%.