Electroreduction of CO₂ to fuels using renewable energy can significantly help in reducing emissions and dependence on fossil fuels. Electrochemical reduction of CO₂ to hydrocarbon fuels (CH_x) is energy inefficient owing to the multistep-multielectron transfer process, which possesses many kinetic limitations. The selective conversion of CO₂ to CO is energy efficient. CO as product can be directly used as a fuel or converted to hydrocarbon fuels by using green hydrogen via Fischer-Tropsch reactions. We have used Ni(M)_x/YSZ based electrodes to study electroreduction of CO₂ on solid oxide cells at high temperature (~800^∘C). Electrodes were developed on commercial standard YSZ supports using Ni(M)_x/YSZ mixtures for cathode and LSM/YSZ mixtures for the anode. Electron microscopy and X-ray diffraction were used to characterize the electrode architecture and material.

The electrodes were tested using online mass spectroscopy and operando Raman spectroscopy. Ni/YSZ electrodes showed sustained performance only when H₂ was added to the fuel mixture, and the reaction proceeded through a reverse water gas shift reaction (RWGS) (CO₂ + H₂ → CO + H₂O) in conjunction with water electrolysis with the CO originating from non-electrochemical RWGS reaction.

The reactions were also analyzed using electrochemical impedance spectroscopy. The pure Ni/YSZ cathodes showed deactivation under a pure CO₂ atmosphere with the formation of NiO_x species with the catastrophic breakdown at high current densities around 400 mA/cm². The behaviour could be verified using both mass spectroscopy and operando Raman Spectroscopy. The electrochemical performance of various electrodes was compared using a 3-electrode geometry. Mixed metal oxide electrodes such as Ni(M) showed improved kinetics, with significant improvement seen in the charge transfer resistance measured.