Red-Light-Mediated Photocatalytic Hydrogen Evolution by Hole Transfer from Non-Fullerene Acceptor Y6

Abstract

One of the highest performing materials in organic photovoltaics is a blend of the polymer donor PM6 and non-fullerene acceptor (NFA) Y6. We report the use of 1:1 PM6:Y6 blend nanoparticles (NPs) prepared by the miniemulsion method for the photocatalytic production of hydrogen under sacrificial conditions, with a 2% mass loading of Pt co-catalyst. When pre- pared using TEBS, a thiophene-containing surfactant, these blend NPs have a desirable inter- mixed morphology. Under ≈1-sun illumination from 400 to 900 nm, hydrogen is produced at a rate of 8000 ± 400 μmol h−1 g−1, which is among the highest reported for organic photocata- lysts under similar conditions. Remarkably, this rate remains high at 5200 ± 300 μmol h−1 g−1 under 650 −900 nm excitation, where Y6 is exclusively excited, generating free charges by hole transfer from Y6 to PM6. The rate drops to 2400 ± 200 μmol h−1 g−1 at 400 −600 nm excitation, where PM6 is preferentially excited and free charges are generated from the conventional electron transfer mechanism. Additionally, external quantum efficiencies of 0.27 ± 0.08% at 405nm, 0.19 ± 0.04% at 565nm, and 0.22 ± 0.02% at 780nm were measured, indicating that this photocatalyst uses a broad region of solar spectrum to yield hydrogen from excitation of both the donor and the acceptor. Transient absorption spectroscopy results show that both hole transfer and electron transfer occur following the excitation of Y6 and PM6, respectively. This work is the first study to show that free charge generation via hole transfer is the dominant mechanism of hydrogen evolution in a donor:NFA blend. This work also highlights the potential that other donor:NFA blends may have for highly efficient green hydrogen production.