Water Spillover to Expedite Two-Electron Oxygen Reduction.

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• The activity-selectivity trade-off limits electrochemical small molecule activation at high current densities.
• Two-electron oxygen reduction (2e- ORR) offers a sustainable pathway for hydrogen peroxide (H2O2) production.
• Existing catalysts struggle to maintain efficiency at industrially relevant current densities.

Purpose of the Study:

• To develop a catalyst that circumvents the activity-selectivity trade-off for 2e- ORR.
• To investigate the mechanism of enhanced 2e- ORR in a fluorine-bridged copper metal-organic framework.
• To demonstrate the scalability and economic viability of H2O2 production using the developed catalyst.

Main Methods:

• Synthesis of a fluorine-bridged copper metal-organic framework.
• Operando spectroscopies (e.g., X-ray absorption spectroscopy, Raman spectroscopy) for in-situ characterization.
• Kinetic studies and theoretical calculations (e.g., Density Functional Theory) to elucidate reaction mechanisms.
• Electrochemical testing across a range of current densities (0.1–2.0 A cm-2).
• Scale-up studies using a 25 cm2 unit module cell.
• Techno-economic analysis for H2O2 production cost.

Main Results:

• The fluorine-bridged copper metal-organic framework catalyst facilitates 2e- ORR via a water spillover effect.
• Water spillover enhances water dissociation and stabilizes the *OOH intermediate under neutral conditions.
• High Faradaic efficiencies (99–84.9%) and H2O2 yield rates (63.17–1082.26 mg h-1 cm-2) were achieved at current densities from 0.1 to 2.0 A cm-2.
• Scalable H2O2 production was demonstrated in a 25 cm2 cell.
• The lowest H2O2 production cost of $0.50 kg-1 was achieved at 2.0 A cm-2.

Conclusions:

• The developed catalyst effectively overcomes the activity-selectivity trade-off in 2e- ORR.
• Water spillover is a key mechanism for enhancing catalytic performance and H2O2 production.
• The system shows significant potential for cost-effective, large-scale H2O2 manufacturing.
• This work offers a new strategy for electrochemical small molecule activation beyond traditional limitations.