Reversing Surface Charge for Highly-Active Organic Photovoltaic Catalysts

Organic photovoltaic materials typically exhibit low charge separation and transfer efficiency and severe exciton/carrier recombination due to high exciton binding energy and short exciton diffusion lengths, limiting the enhancement of photocatalytic hydrogen evolution performance. Here, we introduce a surface charge reversal strategy to regulate the charge character of organic photovoltaic catalyst (OPC). Compared to OPC nanoparticles (NPs) stabilized by an anionic surfactant ((-) NPs), NPs stabilized by a cationic surfactant ((+) NPs) exhibit a raised Fermi level, larger surface band bending and Schottky barrier, thereby enhancing charge separation and transfer efficiency while suppressing charge carrier recombination. As a result, (+) NPs demonstrate better photocatalytic performance than (-) NPs, independent of the chemical structure of OPCs and surfactant molecules. Under the illumination of AM1.5G, 100 mW cm^-2, the PM6: 2FBP-4F NPs stabilized by cationic surfactant (dodecyltrimethylammonium bromide, DTAB) exhibit much higher photocatalytic activity for hydrogen evolution (up to 946.1±15.76 mmol h^-1 g^-1) than that of PM6: 2FBP-4F NPs stabilized by anionic surfactant, among the best results reported so far for photocatalytic hydrogen evolution under simulated sunlight.