Evaluation of the polarization resistance of protonic ceramic electrolysis cells with a triple-component composite electrode

Abstract

Steam-electrolysis performance of protonic ceramics cells with Ni-cermet and triple-component composite electrodes composed of protonic ceramics, mixed proton–electron conductor, and catalysts was evaluated under different operating atmospheres at 500 °C to determine the effects of the catalysts on the electrode performance and electrochemical reaction mechanisms of steam splitting and hydrogen evolution. Here, Ba(Ce0.3Zr0.5Y0.1Yb0.1)O3-δ, (Ba0.95La0.05) (Fe0.8Zn0.2)O3-δ, and La0.8Sr0.2CoO3-δ were used as the protonic ceramics, mixed proton–electron conductor, and catalyst, respectively. Under a fuel-cell atmosphere, the steam vapor pressure (pH2O) at the airside and hydrogen partial pressure (pH2) at the fuel side were held constant at equal levels. In contrast, pH2O was higher and pH2 was lower under the electrolysis atmosphere. The higher pH2O at the airside decreased the air electrode impedance, but the lower pH2 at the fuel side significantly increased the fuel electrode impedance. The La0.8Sr0.2CoO3-δ catalyst facilitated the adsorption and dissociation of steam. Based on the study results, the mechanisms for steam splitting/dissociation at the triple-component composite electrode and hydrogen evolution at the Ni-cermet electrode are suggested.