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.