Detailed analysis of electrochemical behavior of high–performance solid oxide fuel cell using DRT technique

The study of anodic and cathodic reactions separately in a fuel cell with a thin electrolyte is difficult due to the problem in manufacturing a reference electrode because the potential of the reference electrode will depend on the potential of the anode and cathode. This paper presents the results of tests of five types of electrochemical cells. Three of the cells were fuel cells with a supporting nickel–ceramic anode. Two cells were with a supporting electrolyte and symmetrical electrodes similar to the cathode of a fuel cell. A detailed analysis of the impedance spectra of fuel cells using the distribution of relaxation times (DRT) technique, comparison of the obtained data with the DRT functions of symmetrical cells, as well as the use of simple oxides with high electrochemical activity for electrodes impregnation, made it possible to determine separately the polarization resistance of the cathode and anode of the fuel cell and to determine the reasons limiting the power of the cells. It was found that in the case of a high–performance fuel cell (power density more than 2 W cm−2 at 900 °C) its performance was mainly limited by gas diffusion in the pores of the anode.