Electrochemical Behavior of (Fe,Ni)Ox-Based Anodes for Solid-Oxide Fuel Cells in Methane-Containing Atmospheres

Abstract

The work is devoted to investigation of the electrochemical behavior of (Fe,Ni)Ox-based composite anodes in the hydrogen- and methane-containing fuel. Among the studied composites, the optimum electrochemical characteristics were observed for anodes with Fe : Ni ratio approaching 2. In particular, for the electrodes with initial composition 50 vol % Fe0.67Ni0.33Oх–50 vol % Zr0.85Y0.15O1.93 the anode overpotential equals 20–30 mV at a current density of 50–80 mA/cm2 in 10% Н2–Ar–H2O at relatively low temperatures (873–923 K). Increasing current leads to further activation, presumably due to a partial oxidation of metallic particles located at the anode surface. However, the microstructure degradation of the anode layers still represents a significant problem for their utilization. Testing of the electrocatalytic activity of the anodes fabricated from Ni, Zr0.83Sc0.17O1.92 (ScSZ) and Ce0.9Gd0.1 O2 – δ (GDC) revealed a high activity toward catalytic partial methane oxidation with the subsequent electrochemical oxidation of the conversion products, as well as formation of carbonaceous deposits at the nickel surface. The methane conversion degree on Ni-anode comes to 60–90% and decreases with time and on cooling. The doping of nickel oxide with iron lowers the conversion degree and promotes the carbon poisoning, supposedly, because of the lowering of the anodic current density resulting from the worsening of the electrochemical activity.