Co nanoparticles decorated with in-situ exsolved oxygen-storage CeO₂ for an efficient and stable electrolysis of pure CO₂

The valorization of the CO₂ greenhouse gas is important in decarbonization using the renewable energies. Intermediate temperature solid oxide electrolysis cells (SOEC) working at around 800 °C can be useful in activating the strong C⁼O bond (799 kJ mol⁻¹) in CO₂ for the production of CO and decreasing the precious electricity by partially using the heat instead. Ceria/Co doping on the stable chromite is employed to design a composite oxide/metal cathode with a unique ceria decorating Co⁰ for the direct CO₂ electrolysis. The in situ outgrowth of Co0 from the B site activates the ceria exsolution from the A site, or vice versa, producing a well-adhered heterojunction for the activation of CO₂. A high current and stable density above 1 Acm⁻² for 300 h is obtained at a bias of 1.3 V for the CO₂ at a Faraday efficiency close to unity. The higher electrochemical performance of the cell with Ce/Co⁰ codoped cathode is explained by the oxygen storage property of the ceria rather than the direct activation of CO₂ over ceria. This work presents a novel method of constructing metal/oxide cathode for efficient CO₂ analysis and in-depth mechanistic explanation for the metal/oxide hetero-structure in CO₂ activation.