Initial Quenching Efficiency Determines Light-Driven H2 Evolution of [Mo3S13]2- in Lipid Bilayers

Nature uses reactive components embedded in biological membranes to perform light-driven photosynthesis. Here, a model artificial photosynthetic system for light-driven hydrogen (H-2) evolution is reported. The system is based on liposomes where amphiphilic ruthenium trisbipyridine based photosensitizer (RuC9) and the H-2 evolution reaction (HER) catalyst [Mo3S13](2-) are embedded in biomimetic phospholipid membranes. When DMPC was used as the main lipid of these light-active liposomes, increased catalytic activity (TONCAT similar to 200) was observed compared to purely aqueous conditions. Although all tested lipid matrixes, including DMPC, DOPG, DPPC and DOPG liposomes provided similar liposomal structures according to TEM analysis, only DMPC yielded high H-2 amounts. In situ scanning electrochemical microscopy (SECM) measurements using Pd microsensors revealed an induction period of around 26 minutes prior to H-2 evolution, indicating an activation mechanism which might be induced by the fluid-gel phase transition of DMPC at room temperature. Stern-Volmer-type quenching studies revealed that electron transfer dynamics from the excited state photosensitizer are most efficient in the DMPC lipid environment giving insight for design of artificial photosynthetic systems using lipid bilayer membranes.

Automated summary

Nature utilizes reactive components in biological membranes for light-driven photosynthesis. A model artificial photosynthetic system for light-driven hydrogen (H-2) evolution based on liposomes has been developed, with DMPC showing increased catalytic activity compared to other lipid matrixes. In situ scanning electrochemical microscopy measurements reveal an activation mechanism induced by the fluid-gel phase transition of DMPC.