Anthraquinone Redox Relay for Dye-Sensitized Photo-electrochemical H₂ O₂ Production

Anthraquinone (AQ) redox mediators are introduced to metal-free organic dye sensitized photo-electrochemical cells (DSPECs) for the generation of H₂ O₂ . Instead of directly reducing O₂ to produce H₂ O₂ , visible-light-driven AQ reduction occurs in the DSPEC and the following autooxidation with O₂ allows H₂ O₂ accumulation and AQ regeneration. In an aqueous electrolyte, under 1 sun conditions, a water-soluble AQ salt is employed with the highest photocurrent of up to 0.4 mA cm^-2 and near-quantitative faradaic efficiency for producing H₂ O₂ . In a non-aqueous electrolyte, under 1 sun illumination, an organic-soluble AQ is applied and the photocurrent reaches 1.8 mA cm^-2 with faradaic efficiency up to 95 % for H₂ O₂ production. This AQ-relay DSPEC exhibits the highest photocurrent so far in non-aqueous electrolytes for H₂ O₂ production and excellent acid stability in aqueous electrolytes, thus providing a practical and efficient strategy for visible-light-driven H₂ O₂ production.