The CO₂ electrolysing mechanism in single-phase mixed-conducting cathode of solid oxide cell

Area of Science:

• Electrochemistry
• Materials Science
• Chemical Engineering

Background:

• Solid oxide cells (SOCs) require understanding electrochemical mechanisms in mixed ionic-electronic conducting (MIEC) electrodes.
• Chemical capacitance in MIEC materials can obscure polarization behavior during electrochemical testing.
• Accurate modeling is needed to differentiate capacitive current from Faradaic current in SOCs.

Purpose of the Study:

• To develop a multiphysical model for solid oxide electrolysis cells (SOECs) with MIEC electrodes.
• To accurately replicate current-voltage (IV) curves and separate electrochemical processes.
• To elucidate the interplay between chemical capacitance and reactions in MIEC electrodes.

Main Methods:

• Development of a numerical multiphysical model based on oxygen species transport.
• Combination of scanning IV and electrochemical impedance spectra (EIS) measurements.
• Analysis under various SOEC operating conditions to separate Faradaic and charging currents.

Main Results:

• The model accurately reproduces SOEC IV curves across different scanning rates.
• Separation of Faradaic and charging currents was achieved, validating the model.
• The study quantifies contributions of bulk and surface diffusion of oxygen species.

Conclusions:

• The developed model effectively simulates SOEC performance with MIEC electrodes.
• Understanding chemical capacitance effects is crucial for accurate electrochemical analysis.
• This work provides insights into current generation mechanisms in MIEC electrodes.