Characterization of solid oxide fuel cells based on solid electrolytes or mixed ionic electronic conductors

摘要

The relation between cell voltage (V_(Cell)), applied chemical potential difference (Δμ(O_2)) and cell current (I_t) for solid oxide fuel cells (SOFC) based on mixed ionic electronic conductors is derived by considering also the effect of electrode impedance. Four-probe measurements, combined with current interruption analysis, are considered to yield the relation between ionic current (I_i) and overpotential (η). The theoretical relations are used to analyze experiments on fuel cells with Ce_(0.8)Sm_(0.2)O_(1.9) and Ce_(0.8)Gd_(0.2)O_(1.9) electrolytes with La_(0.8)Sr_(0.16)CoO_3 or Pt as the cathode and Ni/Ce_(0.9)Ca_(0.1)O_(1.9-x) or Pt as the anode. The electrode overpotentials of these cells, determined by current interruption measurements, are discussed assuming different models including impeded mass transport in the gas phase for molecular and monoatomic oxygen and Butler-Volmer type charge transfer overpotential.