Second-Shell N Dopants Regulate Acidic O₂ Reduction Pathways on Isolated Pt Sites

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Platinum (Pt) is a benchmark catalyst for the acidic oxygen reduction reaction (ORR), essential for energy conversion.
• Controlling the ORR pathway in single-atom catalysts (SACs) is challenging due to complex coordination environments.

Purpose of the Study:

• To investigate how neighboring nitrogen (N) dopants influence the electronic structure of Pt single atoms.
• To demonstrate the tuning of ORR selectivity (O2-to-H2O vs. O2-to-H2O2) in Pt-N-C SACs.

Main Methods:

• Synthesis of carbon nanotube supported Pt-N-C single-atom catalysts.
• Utilized X-ray-radiated spectroscopy and shell-isolated nanoparticle-enhanced Raman spectroscopy.
• Employed theoretical modeling for comprehensive analysis.

Main Results:

• Achieved tunable O2-to-H2O2 selectivity from 10% to 85% at 0.3 V by altering N dopant coordination.
• Pyridinic- and pyrrolic-N coordination favored the 4-electron ORR pathway.
• Second-shell graphitic-N introduction weakened *OOH binding, promoting the 2-electron ORR pathway.

Conclusions:

• The local chemical environment, specifically N dopant coordination, is critical for steering ORR selectivity in Pt SACs.
• Demonstrated a strategy to precisely control electrochemical performance by manipulating the coordination sphere of single-atom catalysts.