Efficient conversion of CO2 in solid oxide electrolytic cells with Pd doped perovskite cathode on ceria nanofilm interlayer

•CO2 conversion into dry CO and syngas in the symmetrical tubular Solid Oxide Electrolysis Cells.•No additional reducing gas required.•50 h of operation using cyclic load without significant degradation.•Voltage (overpotential) losses in the electrodes were only 200 mV at 350 mA cm−2 current density.•Scalable and modular cells and reactor design.

The conversion of CO2 into high energy density fuels and chemicals using electricity generated from renewable sources in High Temperature Solid Oxide Electrolysers is one of the emerging energy storage technologies. By utilising waste heat from industrial processes or solar concentrators or nuclear reactors, HT-SOE devices can reduce the electrical energy input up to 30%. Thus such devices are attractive for utilising CO2 as a renewable energy storage media when coupled with Solar Concentrator Photovoltaic systems. Application of traditional solid oxide fuel cell electrodes such as Ni-YSZ restricts the operation of the electrolyser to using CO2 mixed with reducing gases such as hydrogen or CO to prevent re-oxidation of metallic Ni to NiO in the presence of CO2. Furthermore carbon deposition can occur at high current densities in dry CO2. New redox stable ceramic cathodes (CO2 electrode) are promising alternatives to Ni-YSZ electrodes. In this work, we report electrochemical performance of Palladium (Pd) doped La0.6Sr0.4Co0.2Fe0.8O3−ᵹ (LSCF-Pd) as potential cathode for these devices. Using LSCF-Pd as both anode and cathode, with nanocrystalline thin film doped ceria as an interlayer between the cathode and the electrolyte, current densities in excess of 360 mA cm−2 were obtained at 800 °C in electrolyte supported tubular cells with high CO2 and steam conversion to syngas. The electrochemical performance of the electrode was found to be stable during the 50 h testing of the cell on cyclic load. The cells and reactors used are modular and scalable.

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