Preparation-Dependent Photocatalytic Hydrogen Evolution by Organic Semiconducting Nanoparticles

The molecular packing, intermixing, and crystallinity of organic semiconductors are crucial in determining the performance of photovoltaic and photocatalytic systems. The effects of these factors on performance have been thoroughly investigated for organic thin-film photovoltaic systems, but not for nanoparticulate organic photocatalytic systems, as the control of molecular packing has been limited and is challenging for nanoparticulate systems. Here, we investigate how the miniemulsion (ME), reprecipitation (RP), and a cold RP method affect molecular packing and, in turn, the photocatalytic performance of nanoparticles (NPs), using the nonfullerene acceptor Y6 alongside conjugated polymer donors P3HT and PIDT-T8BT. RP and cold RP-based neat Y6 NPs exhibit increased performance relative to the ME-based neat Y6 NPs due to greater exciton dissociation. The cold RP-based neat Y6 NPs produce hydrogen at a rate of 8 mmol g^-1 h^-1, which is similar to other previously studied high-performing catalysts, but without the need for a donor material. P3HT:Y6 NPs exhibit low photocatalytic performance, which is likely due to the high miscibility of P3HT and Y6 as well as the low mobility of holes in P3HT domains. In contrast, the PIDT-T8BT:Y6 NPs exhibit significant rates of hydrogen evolution. The RP-based PIDT-T8BT:Y6 NPs outperform the ME and cold RP-based NPs due to a higher degree of intermixing. This work highlights the need to carefully consider the NP preparation method when preparing photocatalytic systems due to its extensive and significant effect on material morphology and, in turn, performance.