Colloidal quantum dots (QDs) have demonstrated great promise in artificial photosynthesis. However, the ultrasmall size hinders its controllable and effective interaction with cocatalysts. To improve the poor interparticle electronic communication between free QD and cocatalyst, we design here a self-assembled architecture of nanoparticles, QDs and Pt nanoparticles, simply jointed together by molecular polyacrylate to greatly enhance the rate and efficiency of interfacial electron transfer (ET). The enhanced interparticle electronic communication is confirmed by femtosecond transient absorption spectroscopy and X-ray transient absorption. Taking advantage of the enhanced interparticle ET with a time scale of ∼65 ps, 5.0 mL of assembled CdSe/CdS QDs/cocatalysts solution produces 94 ± 1.5 mL (4183 ± 67 μmol) of molecular H2 in 8 h, giving rise to an internal quantum yield of ∼65% in the first 30 min and a total turnover number of >1.64 × 107 per Pt nanoparticle. This study demonstrates that self-assembly is a promising way to improve the sluggish kinetics of the interparticle ET process, which is the key step for advanced H2 photosynthesis.