Manipulating the oxygen reduction reaction pathway on Pt-coordinated motifs

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Electrochemical oxygen reduction can yield either water (4e pathway) for energy conversion or hydrogen peroxide (2e pathway) for production.
• Platinum (Pt) is a key catalyst for oxygen reduction, but selectivity control in single-atom catalysts remains challenging.
• Understanding the local coordination environment of Pt is crucial for directing the oxygen reduction reaction pathway.

Purpose of the Study:

• To investigate how the coordination environment of carbon-supported platinum single-atom catalysts affects oxygen reduction selectivity.
• To control the production of hydrogen peroxide versus water during electrochemical oxygen reduction.
• To establish structure-activity relationships for tuning the oxygen reduction reaction pathway.

Main Methods:

• Synthesis of a series of carbon-supported Pt single-atom catalysts with varied neighboring dopants (e.g., C, N, S).
• Electrochemical characterization to determine product selectivity (H2O2 vs. H2O) and catalytic activity.
• Computational energetic analysis to elucidate reaction mechanisms and intermediate pathways.

Main Results:

• Modifying the Pt coordination environment from Pt-C to Pt-N-C and Pt-S-C successfully tuned H2O2 selectivity from 23.3% to 81.4%.
• The turnover frequency ratio of H2O2/H2O was significantly altered, ranging from 0.30 to 2.67 at 0.4 V vs. RHE.
• Increasing Pt site density on Pt-N-C catalysts decreased H2O2 selectivity from 70% to 20%, indicating a controllable branching pathway.

Conclusions:

• The local coordination environment of Pt single-atom catalysts is a critical factor in controlling the oxygen reduction pathway.
• Pt-N-C and Pt-S-C motifs favor H2O2 production, while Pt-C favors H2O formation, via different *OOH intermediate reactions.
• This study provides insights for designing catalysts with tailored selectivity for specific electrochemical applications, such as H2O2 production or efficient energy conversion.