This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.High temperature solid oxide cells are attractive electrochemical reactors to perform simultaneous reduction of steam and CO 2 into syngas with the possibility of delivering a tailored composition to downstream processes. The main thermodynamic considerations, performance and impedance curves of electrolyte supported cells in co-electrolysis are shown as a function of temperature and pressure. In dynamic operation, the thermal changes that the reactor undergoes appear stronger in co-electrolysis mode than in steam electrolysis and should be considered in the development of operating strategies.

Lanthanum strontium chromite (LSC) perovskite partially doped with 15% of Ni on the B-site as reducible transition metal was investigated with the aim to perform in situ exsolution under reducing conditions. A-site deficient compounds were formulated to enhance the exsolution of the electrocatalyst. Single phase is achieved with the formulation La0.65Sr0.3Cr0.85Ni0.15O3-δ (L65SCN) and has been characterized by X-ray diffraction (XRD), Rietveld refinement and scanning electron microscopy (SEM). Exsolution was investigated under reducing conditions in which Ni exsolution was confirmed. Such electrocatalyst was implemented into an electrolyte-supported-cell (ESC) for early electrochemical investigation. Cells were manufactured by screen printing of composite L65SCN/CGO as fuel electrode and La0.58Sr0.4Fe0.8Co0.2O3-δ (LSCF) as air electrode on CGO-3YSZ-CGO substrates. These cells were characterized in steam electrolysis at 930°C by Electrochemical Impedance Spectroscopy (EIS). Further microstructural engineering and fine tuning of the manufacturing parameters are essential for a practical use of this electroctalyst for H2O/CO2 co-electrolysis operation.

Solid oxide electrolysis presents the unique feature to allow simultaneous reduction of steam and CO2 into a highly valuable CO+H2 syngas mixture. Both mainstream solid oxide cell architectures, namely anode supported cells (ASCs) and electrolyte supported cells were investigated in co-electrolysis operation. It is found that, ASCs suffer from microstructural instability of the fuel electrode characterized by a migration of nickel away from the interface with the electrolyte as in steam electrolysis. This holds especially true when operated at high temperature, large steam content and large overpotential. Microstructural optimization may be required to enhance durability. Moreover, the thermodynamic of CO2 reduction that differs from the one of steam, is found to induce stronger thermal effects, when operated in dynamic operation. This requires the development of an operational strategy to minimize potential temperature gradient within the stack when dynamic operation is considered.

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