Conductivity-Dependent Completion of Oxygen Reduction on Oxide Catalysts

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• The oxygen reduction reaction (ORR) is crucial for energy conversion technologies.
• Understanding factors influencing the number of electrons transferred in ORR is key to improving efficiency.
• Intensive properties like electron transfer are typically not considered conductivity-dependent.

Purpose of the Study:

• To investigate the dependence of electron transfer on electric conductivity during the oxygen reduction reaction.
• To explore how catalyst conductivity and carbon content affect the ORR pathway.
• To provide a model explaining the observed conductivity dependency.

Main Methods:

• Investigated four perovskite oxide catalysts with varying conductivities and carbon contents.
• Analyzed the number of electrons transferred during the oxygen reduction reaction.
• Employed a microscopic ohmic polarization model to describe experimental observations.

Main Results:

• Increased conductivity, from both catalysts and carbon additives, promoted a higher number of electrons transferred.
• This resulted in a more complete 4-electron reduction of oxygen.
• The rate-determining step shifted from a two-step 2-electron process to a single-step 1-electron process.

Conclusions:

• Electric conductivity significantly influences the electron transfer number in the oxygen reduction reaction.
• Enhanced conductivity creates more favorable conditions for a complete 4e ORR pathway.
• The microscopic ohmic polarization model effectively explains the experimental findings.