High Temperature Steam Electrolysis (HTSE) through a solid oxide electrolytic cell (SOEC) has been receiving more and more attention recently because of its high conversion efficiency (45~59%) and its potential usage for large-scale hydrogen production. The main works of this manuscript are NiO-YSZ/YSZ (yttria-stabilized zirconia) metal composite ceramics fabrication technique and its application in cathode/electrolyte system of planar SOEC cathodic performances. The relationship between the microstructure of the composite cathode and its corresponding electrochemical properties were investigated. The effects of operating temperature, steam content, reducing speed and running time on the cathode performance were also studied.
The composite powders NiO-YSZ are usually prepared by mixing NiO and YSZ phases together. Generally, the particle size and distribution of the two phases influence the three phase boundary (TPB) length, which is one of the key factors to determine the performance of SOEC cathode. A situ-precipitation method was used here to prepare NiO-YSZ composite powders. The product has a specific surface area of 10.2m²/g and an average particle size of 0.6μm. NiO-YSZ cathode substrate (NiO-YSZ and flour was mixed in the weight ratio of 5:1) was manufactured by dry-pressing method, then YSZ electrode and YSZ-La_0.8Sr_0.2MnO₃ (LSM) anode were screen-printed on the NiO-YSZ substrate. When the Ni/YSZ cathode was feed with 50% H₂O + 50% H₂at a rate of 25 ml/min, a current density of −0.8A/cm²was obtained at 1.5V and 900℃ , which was two times higher than that of NiO-YSZ powders prepared by conventional co-precipitation method.