Photocurrent generation based on a light-driven proton pump in an artificial liquid membrane

Area of Science:

• Artificial photosynthesis
• Bio-inspired energy systems
• Molecular electronics

Background:

• Biological proton pumps harness light to create proton gradients across membranes.
• Photochromic spiropyrans interconvert between forms with different acidities (pKa values).
• Spiropyrans have not previously been utilized for light-driven proton pumping or electrical current generation.

Purpose of the Study:

• To engineer an artificial light-harvesting system capable of generating a proton flux and electrical current.
• To investigate the potential of spiropyran-based systems for light-driven energy conversion.

Main Methods:

• Fabrication of a supported liquid membrane doped with a spiropyran photochromic compound.
• Utilizing ultraviolet (UV) and visible light irradiation to induce reversible spiropyran-to-merocyanine conversion.
• Asymmetric illumination of the membrane to drive proton transport and generate a proton gradient.

Main Results:

• Demonstrated a light-induced proton flux across the membrane.
• Achieved an electrical current with approximately 0.12% efficiency.
• Measured an open-circuit voltage of ~210 mV and a membrane proton gradient of ~3.6 ΔpH units.
• Showcased alternating current generation by alternating light exposure sides.

Conclusions:

• An artificial light-harvesting system based on spiropyran can effectively function as a light-driven proton pump.
• The system efficiently converts light energy into proton flux and electrical current.
• This technology holds promise for novel energy conversion and storage applications.