Solar-driven photocatalytic hydrogen production thiophene-quinoxaline-based polymer dots with tunable molecular weight

Organic conjugated polymer dots (Pdots) are considered promising photocatalysts for solar-driven hydrogen production. However, the impact of molecular weight on their photocatalytic activity remains unexplored. In this study, four thiophene-quinoxaline (PTQ)-based Pdots (D-A system) with tunable molecular weights were fabricated to elucidate the effects of molecular weight on Pdot photocatalytic activity. These Pdots serve as highly efficient and stable photocatalysts for visible-light-driven hydrogen generation in a solvent-free organic system, which was achieved for the first time. Low-molecular-weight Pdots exhibited minimal aggregation, small particle sizes, uniform morphology, enhanced charge transfer capability, and superior photocatalytic activity with remarkable photostability. Notably, L-PTQ10 and L-PTQ11 demonstrated exceptional hydrogen evolution rates of 15,807 and 10,411 μmol g⁻¹ h⁻¹, respectively, when coupled with a Pt cocatalyst. The findings from our DFT and molecular dynamics (MD) calculations strongly support our hypothesis, highlighting the use of low-molecular-weight PTQ-based Pdots as a promising strategy to develop efficient and stable photocatalysts for solar-driven hydrogen production.