Characterization of CuO/YSZ High Temperature Electrolysis Cathode Material Fabricated by High Energy Ball-Milling: 900 °C Reduced by Hydrogen Exposure*

Abstract

Abstract As a more economical cathode material than conventional Ni/YSZ cermet for high temperature electrolysis (HTE) cell, CuO/YSZ composites (40 vol.-% and 60 vol.-% CuO powder with balance YSZ) were successfully fabricated by high energy ball-milling of CuO and YSZ powders, pressing into pellets (Φ 13 mm × 2 mm) and subjecting them to a subsequent reduction-sintering process at 900 °C under purging with a 5 % H2/Ar gas. The Cu/YSZ cermet material thus fabricated was characterized using various analytical methods such as XRD, SEM, and laser diffraction as well as scattering method. Electrical conductivity of reduction-sintered Cu/YSZ cermet pellets thus fabricated was measured both at room temperature and temperature range between 600 °C and 800 °C by using the 4-probe technique for comparison with those of previously published literature conductivity data of Ni/YSZ and Cu/YSZ cermets produced by the same high-energy ball milling of blended elemental metal with YSZ powders. The effect of composite composition on the electrical conductivity was investigated and a slight decrease in electrical conductivity for CuO content of 60 vol.-% was explained by a greater porosity accompanying reduction-sintering of 60 vol.-% CuO/YSZ composite than that with 40 vol.-%. Lastly, CuO/YSZ was used as a HTE cathode of a self-supporting planar unit cell and its electrochemical performance was investigated.