Photosensitized Hydrogen Evolution on a Floating Electrocatalyst Coupled to Electrochemical Recycling.

Photoexcited protonated tetrathiafulvalene (HTTF+) was found to act as a photosensitizer, injecting electrons into Pt microparticles (floating electrocatalysts) to produce H2 and TTF•+ in acidic acetonitrile. In addition, TTF•+ was electrochemically reduced back to TTF on a carbon electrode, to be further protonated to continuously produce H2 photochemically. The onset potential for the electrochemical recycling of TTF•+ on carbon was set at a potential 500 mV more positive than the potential required for the direct reduction of protons. HTTF+ showed no signs of decomposition after 51 h of continuous recycling and photoinduced production of H2, proving stability and reversibility.