Performance of Ni/Y2O3-Stabilized ZrO2 Cermet Cathode Prepared by Mechanical Alloying for High-Temperature Electrolysis of Water Vapor

Abstract

A Ni/Y2O3-stabilized ZrO2 composite cathode was fabricated by high-energy ball milling of Ni and Y2O3-stabilized ZrO2 powders for high-temperature electrolysis (HTE) of water vapor. The composite powder composition, time and rotation speed of ball milling were optimized by trial and error for suitable performance with the maximum efficiency of the fabricated cathode in high-temperature electrolysis of water vapor (steam) at 800 °C. Thus-synthesized composite powders were characterized using various analytical tools, such as X-ray diffraction (XRD), scanning electron microscopy (SEM), and particle size analysis (PSA), and a self-supporting planar unit cell was prepared with a Ni/Y2O3-stabilized ZrO2 composite cathode and a Pt paste anode screen-printed on each side of a Y2O3-stabilized ZrO2 electrolyte disc (30 mm in diameter) and then sintered at 1450 °C for high-temperature electrolysis. XRD and PSA results showed that ball milling parameters, such as ball milling time and rotation speed, affect the crystallinity, average particle size, and particle size distribution of ball-milled Ni/Y2O3-stabilized ZrO2 composites. The effects of cathode and Y2O3-stabilized ZrO2 electrolyte thicknesses on the efficiency of hydrogen production were investigated using a self-supporting planar HTE unit cell operating at 800 °C. The engineering significance of high-energy ball milling (HEBM) is evident: HEBM is approximately equivalent to 60 µm screen printing over the Y2O3-stabilized ZrO2 electrolyte and could obviate a tedious and time-consuming screen-printing process in the fabrication of a cathode.