Backbone Heterojunction Photocatalysts for Efficient Sacrificial Hydrogen Production

Abstract A common strategy to improve the efficiency of organic photocatalysts for hydrogen production from aqueous mixtures is to create bulk heterojunction nanoparticles comprised of intermixed donor and acceptor phases that allow for efficient charge separation after photoexcitation. However, many of these systems possess poor stability due to aggregation of these nanoparticles under operating conditions. Moreover, the use of surfactants, that inhibit aggregation and promote donor–acceptor phase intermixing, can form an insulating barrier that reduces the photocatalytic efficiency of these nanoparticles. Here, these issues are bypassed by preparing a single‐component organic heterojunction‐type polymer, P40 , in which a molecular donor, pyrene, is tethered to poly(fluorene‐ co ‐dibenzo b , d thiophene sulfone), a conjugated polymer acceptor. By tethering the donor and acceptor together, phase intermixing is guaranteed without the need for costly post‐synthesis processing or insulating surfactants. Moreover, the influence of pyrene in P40 is determined to be multifaceted, as it influences the dynamics of the excited state, the aggregate microstructure, and the local solvent environment. P40 is found to have an exceptional external quantum efficiency of 38% at 420 nm in the presence of triethylamine as a hole scavenger, the highest value reported for any linear conjugated polymer to date for sacrificial hydrogen production.