Breathing air into water: dual-pathway H2O2 synthesis via aerating amphiphilic supramolecular films

Abstract

Dual-pathway photosynthesis offers a sustainable method for producing hydrogen peroxide (H2O2) from air and water. The main efficiency-limiting step in existing photocatalytic systems is the simultaneous triphasic enrichment and activation of gaseous air and liquid water at the solid catalyst interface. In this work, utilizing the amphiphilic molecular design and hierarchical self-assembly of asymmetric perylene diimide molecules (PDIOH), we developed an O2-permeable 2D organic supramolecular film for dual-pathway H2O2 production. The resulting supramolecular films amplify the amphiphilic characteristics of PDIOH molecules, featuring Janus wettability on both sides, which anisotropically enrich and activate O2 and H2O molecules. Specifically, non-polar O2 is enriched on the hydrophobic surface of the PDIOH films and then photo-reduced to the polar ·O2- species, which subsequently detaches and enters the aqueous phase, mimicking the process of "breathing air into water." Simply placing PDIOH films at the static air-water interface achieves a high H2O2 yield of 3046.15 µmol·g-1·h-1 without the need for stirring, O2 bubbling or small molecule sacrificial agents. This setup allows for the continuous flow synthesis of H2O2 with a stable efflux concentration of at least ~800 µM.