20-Fold Increased Limiting Currents in Oxygen Reduction with Cu-tmpa by Replacing Flow-By with Flow-Through...

Area of Science:

• Electrochemistry
• Green Chemistry
• Catalysis

Background:

• Electrochemical oxygen reduction offers a sustainable route for hydrogen peroxide (H2O2) production.
• Current industrial H2O2 synthesis faces limitations due to O2 solubility and mass transfer issues.
• H2O2 is a key green oxidant with diverse applications in industry and environmental remediation.

Purpose of the Study:

• To investigate the impact of electrode configuration and flow conditions on H2O2 production in electrochemical flow cells.
• To compare flow-by and flow-through reactor designs for H2O2 synthesis.
• To evaluate the suitability of suspension electrodes for electrochemical H2O2 production.

Main Methods:

• Testing flow-by and flow-through electrochemical flow cell configurations.
• Utilizing a homogeneous copper-based catalyst (Cu-tmpa) in a neutral buffer.
• Monitoring H2O2 production and estimating limiting current density via cyclic voltammetry (CV).
• Assessing the role of activated carbon (AC) in suspension electrodes.

Main Results:

• The flow-through configuration demonstrated a 15-20 times higher geometrical limiting current density and enhanced H2O2 production compared to the flow-by setup.
• Suspension electrodes with AC material were found to decompose H2O2, rendering them unsuitable for synthesis.
• While microscale mass transfer was improved in the flow-through system, maintaining current density and Faradaic efficiency (FE) at high production rates presented challenges.

Conclusions:

• Flow-through reactor design significantly enhances H2O2 production and mass transfer compared to flow-by systems.
• Activated carbon is detrimental to H2O2 synthesis due to catalytic decomposition.
• Optimizing reactor design and operating conditions is crucial for scaling up electrochemical H2O2 production while maintaining high FE and current density.