H₂O₂ Synthesis with Molecular Electrocatalysts Enables Substantial Current Densities in a Flow Cell Using Gas...

Area of Science:

• Electrochemistry
• Catalysis
• Materials Science

Background:

• Molecular catalysts for the two-electron oxygen reduction reaction (ORR) producing hydrogen peroxide (H2O2) are of significant interest.
• Previous studies were limited to rotating disk electrode (RDE) setups, hindering evaluation in industrially relevant configurations.
• Mass transport limitations in RDEs restrict the assessment of true catalytic currents for molecular ORR catalysts.

Purpose of the Study:

• To evaluate the performance of a copper-based molecular ORR catalyst, Cu-(tmpa), in a gas diffusion electrode (GDE) cell configuration.
• To identify factors influencing catalytic current and H2O2 generation in a GDE setup.
• To assess the potential of molecular catalysts in industrially relevant reactor configurations.

Main Methods:

• Utilized a readily assembled GDE cell to test the Cu-(tmpa) catalyst.
• Investigated the impact of buffer concentration, catalyst concentration, and GDE composition on catalytic current.
• Operated the Cu-(tmpa) catalyst in a GDE flow cell for extended periods.

Main Results:

• Cu-(tmpa) demonstrated sustained H2O2 generation over multiple hours in the GDE flow cell.
• Achieved a Faradaic efficiency of 50% and a production rate of 0.11 mmol cm⁻² h⁻¹ at -20 mA/cm².
• GDE configuration increased current density by nearly 10 times compared to RDE, with altered selectivity trends favoring H2O2 at higher currents.

Conclusions:

• The GDE setup enables a comprehensive assessment of molecular ORR catalyst potential beyond idealized RDE conditions.
• Cu-(tmpa) shows promise as an H2O2-generating catalyst in a GDE configuration, suitable for practical applications.
• Well-defined active sites of molecular catalysts can be effectively utilized in emerging H2O2 production technologies.