Optimally Miscible\nPolymer Bulk-Heterojunction-Particles\nfor Nonsurfactant Photocatalytic Hydrogen Evolution

Mini-emulsion and\nnanoprecipitation techniques relied\non large\namounts of surfactants, and unresolved miscibility issues of heterojunction\nmaterials limited their efficiency and applicability in the past.\nThrough our molecular design and developed surfactant-free precipitation\nmethod, we successfully fabricated the best miscible bulk-heterojunction-particles\n(BHJP) ever achieved, using donor (<b>PS</b>) and acceptor (<b>PSOS</b>) polymers. The structural similarity ensures optimal\nmiscibility, as supported by the interaction parameter of the <b>PS</b>/<b>PSOS</b> blend is positioned very close to the\nbinodal curve. Experimental studies and molecular dynamics simulations\nfurther revealed that surfactants hinder electron output sites and\nreduce the concentration of sacrificial agents at the interface, slowing\npolaron formation. Multiscale experiments verified that these BHJP,\napproximately 12 nm in diameter, further form cross-linked fractal\nnetworks of several hundred nanometers. Transient absorption spectroscopy\nshowed that BHJP facilitates polaron formation and electron transfer.\nOur BHJP demonstrated a superior hydrogen evolution rate (HER) compared\nto traditional methods. The most active BHJP achieved an HER of 251.2\nmmol h<sup>–1</sup> g<sup>–1</sup> and an apparent quantum\nyield of 26.2% at 500 nm. This work not only introduces a practical\nmethod for preparing BHJP but also offers a new direction for the\ndevelopment of heterojunction materials.