Balancing Activity and Selectivity in Two-Electron Oxygen Reduction through First Coordination Shell Engineering in...

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• The electrochemical two-electron oxygen reduction reaction (2e- ORR) is a promising route for sustainable hydrogen peroxide (H2O2) production.
• Selectivity challenges arise from the competing four-electron ORR pathway, limiting H2O2 yield and requiring high overpotentials.

Purpose of the Study:

• To investigate the effect of modulating the coordination sphere of cobalt single-atom catalysts (Co-N-C) on H2O2 selectivity.
• To understand the relationship between catalyst structure, electronic properties, and the 2e- ORR pathway using DFT calculations and experimental validation.

Main Methods:

• First-principles density functional theory (DFT) calculations to model catalyst active sites (Co-NxOy).
• Synthesis of N-doped carbon-supported catalysts featuring Co-NxOy sites.
• Electrochemical evaluation of catalytic activity and H2O2 selectivity in a flow cell.

Main Results:

• DFT predicted that replacing Co-N with Co-O bonds weakens *OOH adsorption, enhancing 2e- ORR selectivity.
• Experimental validation confirmed that catalysts with Co-NxOy sites improve H2O2 selectivity.
• A trans-Co-N2O2 catalyst demonstrated high activity and selectivity, achieving a production rate of 12.86 and 100-hour stability.

Conclusions:

• Modulating the coordination environment of Co single atoms is crucial for selective H2O2 production.
• The Co-N-O active sites offer a promising strategy to overcome selectivity limitations in 2e- ORR.
• This work provides a pathway towards efficient and stable electrochemical H2O2 synthesis.