Rutile-Type Co_0.5Ti_0.5NbO₄-Based Cathode with In Situ Exsolved Metal Particles for Direct CO₂ Electrolysis

Rutile-type Co_0.5Ti_0.5NbO₄ (CTO)-based materials doped with Fe³⁺ or Ni²⁺ were investigated as cathode electrodes to modify their electrical conductivity and electrocatalysis toward CO₂ splitting. Higher electric conductivity was found in Co_0.4Fe_0.2Ti_0.4NbO₄ (CTO-Fe, 0.78 S cm^-1) and Co_0.25Ni_0.25Ti_0.5NbO₄ (CTO-Ni, 2.10 S cm^-1) compared to CTO (0.49 S cm^-1) after the reduction at 800 °C in Ar-5% H₂. Co and Co-Ni particles exsolved in situ from the surface of CTO, CTO-Fe, and CTO-Ni after reduction. CTO-Ni and CTO-Fe cathodes did better in the CO₂ electrolysis at 800 °C than the CTO one, but the CTO-Ni cell was unstable after 10 h of operation due to the carbon deposition that blocked the electrode. The cell with CTO-Fe demonstrated a good stability for CO₂ splitting in 100 h. This work demonstrates that rutile-type CTO-based cathodes are promising to provide an efficient and candidate oxide cathode for the electrolysis of CO₂.