Lanthanum-Based Compounds: Electronic Band-Gap-Dependent Electrocatalytic Materials for Oxygen Reduction Reaction

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• The electronic energy levels of lanthanum compounds significantly influence their performance in the oxygen reduction reaction (ORR).
• Understanding these electronic properties is crucial for designing efficient electrocatalysts.

Purpose of the Study:

• To synthesize and evaluate three lanthanum compounds (LaOHCO₃, La₂ O₂ CO₃, and La₂ O₃) as electrocatalysts for ORR.
• To investigate the correlation between the electronic energy levels and the ORR electrocatalytic activity.

Main Methods:

• In situ urea hydrolysis method for synthesizing lanthanum compounds.
• Annealing at different temperatures to tune material properties.
• Electrochemical measurements in 0.1 M KOH solution to assess ORR performance.

Main Results:

• Layer-structured La₂ O₂ CO₃ exhibited the smallest band gap and optimal conduction band (CB) and valence band (VB) energy levels.
• La₂ O₂ CO₃ demonstrated superior electrocatalytic activity, with minimal hydrogen peroxide (H₂ O₂) production and enhanced durability for ORR.
• The electronic structure of La₂ O₂ CO₃ facilitates electron transfer and strengthens oxygen adsorption during ORR.

Conclusions:

• The electronic energy level is directly correlated with the electrocatalytic ORR activity of lanthanum compounds.
• La₂ O₂ CO₃ is a highly promising electrocatalyst for ORR, owing to its favorable electronic structure and catalytic mechanisms.
• The material's ability to chemically disproportionate hydrogen peroxide further enhances its efficiency for ORR.