Decouple H₂O₂ Electrosynthesis From Microenvironmental Decomposition via Atomic Site Density Engineering

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Electrocatalytic hydrogen peroxide (H₂O₂) production via two-electron oxygen reduction (2e⁻-ORR) is vital for decentralized synthesis and water purification.
• Low Faradaic efficiency in H₂O₂ production is often caused by competing H₂O₂ reduction and disproportionation reactions.
• Controlling catalyst active site density is crucial for managing microenvironmental losses and maximizing H₂O₂ yield.

Purpose of the Study:

• To investigate the impact of active atomic density on microenvironmental losses in electrocatalytic H₂O₂ production.
• To develop a strategy for suppressing side reactions and enhancing net H₂O₂ output using single-atom catalysts (SACs).
• To optimize catalyst design for improved H₂O₂ selectivity and stability in practical applications.

Main Methods:

• Synthesis of defect-rich Cobalt-Nitrogen-Oxygen (Co-N₂O₂) single-atom catalysts (SACs) with varying Co loadings.
• Characterization of catalyst properties, including electronic structure and active site distribution.
• Electrochemical evaluation of H₂O₂ production efficiency, Faradaic efficiency, and selectivity.
• Integration of the optimized catalyst into a flow-through bilayer electrified membrane reactor for pollutant degradation.

Main Results:

• Closely spaced Co-N₂O₂ sites led to inter-site electronic coupling, broadening the d-band and promoting H₂O₂ side reactions.
• Optimal Co loading (0.84 wt.%) in Co/NOC-0.8 significantly suppressed H₂O₂ reduction and disproportionation by increasing the barrier for OH*/O* formation.
• The optimized catalyst reduced secondary H₂O₂ consumption by up to 79%, achieving a practical Faradaic efficiency of 78.7% (vs. 86.5% intrinsic selectivity).
• The electrified membrane reactor with the optimized catalyst demonstrated over 90% single-pass aniline removal for more than 72 hours.

Conclusions:

• Active atomic density engineering is a key principle for controlling microenvironmental losses in SACs for H₂O₂ production.
• Optimized site isolation effectively preserves H₂O₂ from secondary consumption, bridging the gap between intrinsic selectivity and practical efficiency.
• The developed catalyst and reactor system show promise for efficient and stable decentralized chemical synthesis and environmental remediation.