All-Polymer Heterojunction Nanoparticles Enable Reproducible and Enhanced Hydrogen Evolution Photocatalysis

Abstract

Organic semiconducting nanoparticle blends represent a promising platform for renewable photocatalytic hydrogen generation. Their performance strongly depends on microstructure and particle size. Here, we demonstrate the fabrication and characterization of heterojunction nanoparticles made from the donor polymer PM6 and the polymeric acceptor PJ1-R, a polymer analogue of a benchmark small-molecule acceptor Y6. The all-polymer PM6:PJ1-R system exhibited significantly improved photocatalytic performance compared to PM6:Y6 nanoparticles, with an optimal hydrogen evolution rate of 24.89 mmol cm -2 h -1 in the presence of ascorbic acid as a sacrificial oxidant, representing a 2.5-fold increase at optimal blend ratios.Preparation of the all-polymer PM6:PJ1-R nanoparticles was highly reproducible, yielding consistent size distributions (80-120 nm) without aggregation, even after extended storage (12 months), as well as consistent batch-to-batch hydrogen evolution rates. Morphological characterization using transmission electron microscopy revealed beneficial intermixed morphologies with local lamellar ordering, while extensive photophysical analysis (UV-Vis, photoluminescence, timeresolved photoluminescence, and transient absorption spectroscopy) confirmed efficient and complementary charge transfer between PM6 and PJ1-R, with high photoluminescence quenching efficiencies (83.6% for donor, 85.7% for acceptor). These results underline the potential of all-polymer blends in organic semiconductor photocatalysts.