Rutile-Type Co 0.5 Ti 0.5 NbO 4 -Based Cathode with In Situ Exsolved Metal Particles for Direct CO 2 Electrolysis.

Rutile-type Co 0.5 Ti 0.5 NbO 4 (CTO)-based materials doped with Fe 3+ or Ni 2+ were investigated as cathode electrodes to modify their electrical conductivity and electrocatalysis toward CO 2 splitting. Higher electric conductivity was found in Co 0.4 Fe 0.2 Ti 0.4 NbO 4 (CTO-Fe, 0.78 S cm -1 ) and Co 0.25 Ni 0.25 Ti 0.5 NbO 4 (CTO-Ni, 2.10 S cm -1 ) compared to CTO (0.49 S cm -1 ) after the reduction at 800 °C in Ar-5% H 2 . 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 CO 2 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 CO 2 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 CO 2 .