Water Oxidation to Hydrogen Peroxide Over a Super-Aerophilic Graphite Catalyst

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• The two-electron water oxidation reaction (2e-WOR) to produce hydrogen peroxide (H₂O₂) is a promising anode reaction for electrochemical cells, enabling pairing with valuable cathode reactions.
• Development of high-performing and reliable anodic catalysts for 2e-WOR remains a significant challenge.
• Existing graphite catalysts suffer from poor activity and low O₂ binding in electrolyte environments, hindering H₂O₂ generation rates.

Purpose of the Study:

• To rationally design an inexpensive, robust, and selective graphite catalyst electrode for efficient 2e-WOR.
• To investigate strategies for enhancing both the activity and selectivity of graphite-based 2e-WOR catalysts.
• To demonstrate the potential for co-production of valuable chemicals, such as H₂, alongside H₂O₂.

Main Methods:

• Creation of an aerophilic graphite electrode to retain generated O₂ on the surface, shifting intermediate binding towards H₂O₂ production.
• Elemental doping of graphite (N, S, B, P) to improve catalytic activity and selectivity while maintaining O₂ retention.
• Electrochemical characterization and stability testing of the doped graphite catalysts.

Main Results:

• Initial aerophilic graphite showed a seven-fold increase in H₂O₂ selectivity but limited rate improvement.
• Optimized boron-doped graphite catalyst achieved a maximum Faraday efficiency of 60.6 ± 2.6% for H₂O₂ production.
• The B-doped catalyst demonstrated a high production rate (26.7 ± 0.6 µmol min⁻¹ cm⁻²) and excellent stability (>120 h), with simultaneous H₂ co-production FE >90%.

Conclusions:

• A rational design strategy involving aerophilicity and elemental doping effectively enhances graphite catalysts for selective 2e-WOR.
• The developed boron-doped graphite catalyst offers a cost-effective and robust solution for H₂O₂ production.
• This approach highlights the potential for integrated chemical co-production in electrochemical systems.