Unassisted photocatalytic H₂O₂ production under visible light by fluorinated polymer-TiO₂ heterojunction

Photocatalytic H₂O₂ production is one of the most promising methods because it is a safe and sustainable technique. However, the inactiveness of inorganic photocatalysts (TiO₂) under visible light irradiation and severe photodecomposition of H₂O₂ on their surfaces result in low performance for solar H₂O₂ production. Here, we report for the first time, a hydrophobic organic/inorganic (polymer/TiO₂) heterojunction photocatalyst, which not only can utilize visible light, but also suppress H₂O₂ decomposition. In the absence of a hole scavenger, the photogenerated H₂O₂ concentration of the poly(9,9-dioctylfluorene-alt-benzothiadiazole) (PFBT)/TiO₂ heterojunction photocatalyst (67 µM) was >70 times higher than that of pristine PFBT polymer. Further, improvement of polymer hydrophobicity by fluorine substitution results in enhanced photogenerated H₂O₂ concentration (110.4 µM) on (Poly(9,9-dioctyl fluorine-alt-difluorobenzothiadiazole) (PF2FBT)/TiO₂). The atomistic simulation studies substantiate that the low adsorption energy of H₂O₂ on the heterojunction and the surface shielding of TiO₂ induced by the hydrophobicity of the fluorinated polymers significantly improve H₂O₂ production.