Grafted Groups’ Modification in the Main Chain of Polyfluorene‐Based Conjugated Polyelectrolytes to Greatly Boost Solar Hydrogen Production from Natural Seawater

Hydrogen represents an ideal fuel with environmental-friendly properties and high energy density. It is attractive to directly produce clean hydrogen from inexhaustible solar energy and the most abundant seawater on the earth. Nevertheless, the search for highly efficient and stable photocatalysts remains a big challenge so far because of the dissolved salts in natural seawater, which may result in the decomposition of photocatalysts and undesirable side reactions. Herein, three polyfluorene-based conjugated polyelectrolytes (CPEs) with different grafted groups in the polymer backbone for hydrogen production in natural seawater under solar light illumination are reported. The change in the grafted groups on the main chain of CPEs provides them very similar UV light absorption, but PFNH-Br grafted with H group exhibits significantly improved charge transport and lower emission intensity compared with PFN-Br (grafted with C8H17) and PFPABr (grafted with CH2CH2N(CH3)(3)Br). As a result, PFNH-Br yield the highest hydrogen evolution rate (HER) of 1806 mu mol h(-1) g(-1) without external cocatalysts under simulated solar light, while lower HERs of 356 and 225 mu mol h(-1) g(-1) are found for PFN-Br and PFPABr, respectively. This study shows that grafted group optimization is a powerful strategy to maximize the activity of polyfluorene-based CPEs for direct photocatalytic seawater splitting.