Steam electrolysis in a solid oxide electrolysis cell fabricated by the phase-inversion tape casting method

• Dual-layer Ni–YSZ cathode was prepared by the phase-inversion tape casting method.
• Pore formation mechanism of the phase-inversion tape casting process was explained.
• 3D microstructure of the dual-layer Ni–YSZ cathode was first investigated.
• Current density of 2.3 A cm− 2 was achieved at 800 °C, 1.5 V and 33% AH.

In this study, an asymmetric NiO–yttria-stabilized zirconia (YSZ) cathode substrate has been successfully fabricated by the phase-inversion tape casting method. 3-dimensional X-ray microscopy and subsequent analysis demonstrate that the NiO–YSZ substrates exhibit dual-layer structure: a thin sponge-like pore layer is supported on a thick finger-like macro-void layer. The electrochemical performance of the Ni–YSZ/YSZ/YSZ–LSM electrolyzer with this novel dual-layer cathode has been significantly enhanced. The electrolyzer exhibits an excellent current density of 2.3 A cm− 2 and a high H2 production rate of 958 mL cm− 2 h− 1 at 800 °C and 1.5 V, and a polarization resistance of 0.25 Ωcm2 at the open circuit voltage when the cathode and anode are exposed to 33 vol.% H2O–67 vol.% H2 and ambient air, respectively, demonstrating that the thin sponge-like pore layer in the dual-layer cathode can provide sufficient electrochemical reaction sites for H2O reduction, while the thick finger-like macro-void layer can serve as the support for the electrolyzer and facilitate H2/H2O transport in the cathode, reducing the cathode polarization resistance and enhancing the cell performance.