Preparation-Dependent\nPhotocatalytic Hydrogen Evolution\nby Organic Semiconducting Nanoparticles

The molecular packing, intermixing,\nand crystallinity of organic\nsemiconductors are crucial in determining the performance of photovoltaic\nand photocatalytic systems. The effects of these factors on performance\nhave been thoroughly investigated for organic thin-film photovoltaic\nsystems, but not for nanoparticulate organic photocatalytic systems,\nas the control of molecular packing has been limited and is challenging\nfor nanoparticulate systems. Here, we investigate how the miniemulsion\n(ME), reprecipitation (RP), and a cold RP method affect molecular\npacking and, in turn, the photocatalytic performance of nanoparticles\n(NPs), using the nonfullerene acceptor Y6 alongside conjugated polymer\ndonors P3HT and PIDT-T8BT. RP and cold RP-based neat Y6 NPs exhibit\nincreased performance relative to the ME-based neat Y6 NPs due to\ngreater exciton dissociation. The cold RP-based neat Y6 NPs produce\nhydrogen at a rate of 8 mmol g<sup>–1</sup> h<sup>–1</sup>, which is similar to other previously studied high-performing catalysts,\nbut without the need for a donor material. P3HT:Y6 NPs exhibit low\nphotocatalytic performance, which is likely due to the high miscibility\nof P3HT and Y6 as well as the low mobility of holes in P3HT domains.\nIn contrast, the PIDT-T8BT:Y6 NPs exhibit significant rates of hydrogen\nevolution. The RP-based PIDT-T8BT:Y6 NPs outperform the ME and cold\nRP-based NPs due to a higher degree of intermixing. This work highlights\nthe need to carefully consider the NP preparation method when preparing\nphotocatalytic systems due to its extensive and significant effect\non material morphology and, in turn, performance.