Dynamic Valence-State-Adaptive Ta Single-Atom Sites for Artificial H₂O₂ Photosynthesis

Area of Science:

• Photocatalysis
• Green Chemistry
• Materials Science

Background:

• The synthesis of hydrogen peroxide (H₂O₂) via the two-electron oxygen reduction reaction (2e^- ORR) is crucial for sustainable chemical production.
• Understanding the atomic-scale mechanisms of excited-state electron behavior and *in situ* oxygen activation in photocatalysis is essential but remains challenging.

Purpose of the Study:

• To identify optimal single-atom catalysts for H₂O₂ photosynthesis.
• To elucidate the dynamic interplay between active sites, excited-state electrons, and *in situ* O₂ activation at the atomic level.

Main Methods:

• Mechanism-guided integrated strategy combining theoretical screening and experimental construction.
• Utilizing *in situ* characterization techniques (e.g., spectroscopy) and theoretical calculations.
• Identifying tantalum (Ta) single-atom sites on carbon nitride as active centers.

Main Results:

• Achieved an apparent quantum yield of 14.53% at 420 nm and 1.12% solar-to-chemical efficiency for H₂O₂ production in pure water.
• Demonstrated dynamic valence-state evolution of Ta single-atom sites (+4.16 → +4.37 → +3.14) facilitating O₂ adsorption and activation.
• Revealed Ta 5d-O 2p orbital coupling driving end-on O₂ activation and *OOH-mediated H₂O₂ formation.

Conclusions:

• Tantalum single-atom sites are optimal 5d metal centers on carbon nitride for H₂O₂ photosynthesis.
• Dynamic active site adaptation is key to efficient photocatalytic H₂O₂ synthesis.
• Established a framework for designing adaptive single-atom catalysts for artificial photosynthesis.