Proton-coupled electron transfer at SOFC electrodes.

Area of Science:

• Electrochemistry
• Materials Science
• Quantum Mechanics

Background:

• Solid oxide fuel cell (SOFC) electrode efficiency is limited by charge transfer processes.
• Current models often use classical transition state theory, which may not fully capture reaction mechanisms.

Purpose of the Study:

• To develop a novel theoretical framework for charge transfer kinetics at SOFC electrodes.
• To unify electrostatic surface potential with proton-coupled electron transfer.
• To accurately model the hydrogen oxidation/water electrolysis reaction.

Main Methods:

• Derivation of a reaction rate framework incorporating electrostatic potential, dipole moment, electronic structure, and vibronic states.
• Application of the theory to analyze current-voltage characteristics of Ni/gadolinium-doped ceria electrodes.
• Quantification of solvent reorganization energy for SOFC materials.

Main Results:

• The novel model shows excellent agreement with experimental current-voltage data.
• Identified concerted electron and proton tunneling as crucial for the reaction mechanism.
• Provided the first quantification of solvent reorganization energy in SOFCs.

Conclusions:

• The developed theory provides a more accurate description of charge transfer at SOFC electrodes.
• Quantum tunneling plays a significant role in the hydrogen oxidation/water electrolysis reaction.
• The three-phase boundary mechanism is confirmed as dominant for charge transfer in cermet electrodes.