Initial Quenching Efficiency Determines Light-Driven H₂ Evolution of [Mo₃ S₁₃ ]^2- in Lipid Bilayers

Area of Science:

• Artificial photosynthesis
• Biomimetic systems
• Catalysis

Background:

• Nature utilizes membrane-embedded components for photosynthesis.
• Artificial systems aim to mimic natural light-driven processes.
• Hydrogen (H₂) evolution is a key target for sustainable energy.

Purpose of the Study:

• To develop a model artificial photosynthetic system for light-driven H₂ evolution.
• To investigate the role of lipid membranes in enhancing catalytic activity.
• To understand the mechanism of H₂ evolution in liposomal systems.

Main Methods:

• Fabrication of liposomes embedding a ruthenium photosensitizer (RuC₉) and a H₂ evolution reaction (HER) catalyst ([Mo₃ S₁₃]^2-).
• Utilizing DMPC, DOPG, and DPPC as lipid matrixes.
• In situ scanning electrochemical microscopy (SECM) for H₂ evolution monitoring.
• Stern-Volmer quenching studies for electron transfer dynamics.

Main Results:

• DMPC-based liposomes showed significantly increased catalytic activity (TON_CAT ~200) for H₂ evolution compared to aqueous solutions.
• Lipid matrixes provided similar structures, but only DMPC yielded high H₂ yields.
• SECM revealed a ~26-minute induction period, suggesting a DMPC-dependent activation mechanism possibly linked to its phase transition.
• Efficient electron transfer from the photosensitizer was observed in the DMPC lipid environment.

Conclusions:

• Lipid bilayer membranes, particularly DMPC, can enhance artificial photosynthesis for H₂ evolution.
• The fluid-gel phase transition of DMPC may play a role in activating the catalytic process.
• Optimized electron transfer dynamics within the lipid environment are crucial for efficient artificial photosynthesis.