The parallel pathways of hydrogen oxidation reaction on high active decorated Ni–YSZ electrode in electrochemical cell with GDC protective layer

Abstract

In this study, we considered the electrochemical behavior of a symmetrical electrochemical cell with a highly conductive supporting La0.88Sr0.12Ga0.82Mg0.18O2.85 electrolyte, a protective Ce0.82Gd0.18O2–δ layer and highly active Ni + Zr0.84Y0.16O1.92 electrodes in H2 + H2O + Ar gas mixtures at constant partial pressure of H2, H2O and constant ratio pH2/pH2O. It is shown that the presence of a protective Ce0.82Gd0.18O2–δ layer makes it possible to significantly increase the electrode activity by about 7 times at 800 °C and about 24 times at 700 °C. After the introduction of highly dispersed particles of cerium oxide into the electrode by the method of solution impregnation, the polarization resistance of electrode was about 0.03 Ω cm2 at 800 °C. It is shown that in the case of decorated electrodes, the mechanism of hydrogen oxidation includes two parallel pathways. One is similar to the hydrogen oxidation route for conventional nickel–ceramic electrodes, and the second includes slow stages of oxygen ions transport both in ceria particles and in the protective Ce0.82Gd0.18O2–δ layer. It is shown for the first time that with an increase in oxygen partial pressure the ratio of the rates of these pathways changes.