Polarized N⁺-Mediated Charge-Transfer State Drives Two-Electron Water Oxidation.

Area of Science:

• Materials Science
• Photocatalysis
• Surface Chemistry

Background:

• Selective two-electron water oxidation (2e- WOR) for hydrogen peroxide (H2O2) synthesis is crucial for artificial photosynthesis but challenged by competing four-electron oxygen evolution (4e- OER).
• The *OOH intermediate's instability leads to side reactions, favoring the less selective 4e- OER pathway.

Purpose of the Study:

• To engineer a photocatalyst surface for precise control over interfacial water oxidation pathways.
• To stabilize the *OOH intermediate and promote selective 2e- WOR for H2O2 production.

Main Methods:

• Surface engineering of ZnCdS2 photocatalyst with polarized N⁺ surfactants.
• Utilizing charge-transfer (C-T) excited states to modulate surface electronic states.
• Investigating molecular-scale polarization effects on hole potentials and intermediate stabilization.

Main Results:

• Achieved molecular-level control over water oxidation pathways via C-T excited states.
• Demonstrated precise modulation of hole potentials and stabilization of the *OOH intermediate.
• Obtained a H2O2 production rate of 2.37 mmol·g-1·h-1 (20.26 times pristine ZnCdS2) without sacrificial reagents.
• Reached a scalable H2O2 concentration of 1.61 mM in a micro-batch flow reactor.

Conclusions:

• Surface-engineered ZnCdS2 with N⁺ surfactants enables selective 2e- WOR by controlling interfacial charge transfer.
• This strategy stabilizes key intermediates and promotes efficient H2O2 synthesis.
• Highlights the potential of C-T excited states in surface engineering for selective multi-electron photocatalysis.