Electrochemical Characterization of Ni/Y_2O_3-ZrO_2 Hydrogen Electrode for Water Splitting in Solid Oxide Electrolysis Cells

摘要

Ni/Y_2O_3 stabilized ZrO_2 (Ni/YSZ) cermet is a widely used hydrogen electrode for solid oxide fuel cells (SOECs), but detailed studies regarding the water splitting processes are scarce. Here we report the preliminary results on the variation of electrocatalytic activity of Ni/YSZ hydrogen electrodes as a function of operating temperature, water concentration and dc bias. The electrode activity for the water splitting reaction is strongly influenced by varying the water concentration and dc bias. The electrochemical performance for the water splitting reaction decreases with the increase of water concentration. The electrode polarization resistance increases gradually with the increase of dc bias regardless of the H_2O content. The decrease of activity is particularly pronounced in the low frequency impedance process related to the H_2O dissociative adsorption and diffusion processes. This study clearly demonstrates the reaction mechanism and kinetics of the H_2O dissociation reaction.