Hydrogen bonds facilitate spontaneous exciton dissociation
The researchers developed a supramolecular photocatalyst in which hydrogen bonds bridge the electron donor, a perylene diimide supramolecule, and the electron acceptor, an aminated fullerene. These hydrogen bonds create a strongly charge-polarized microenvironment that enhances dielectric screening and weakens the Coulombic attraction between electrons and holes. Further analysis revealed that the hydrogen bonds provide directional bridges for exciton delocalization. By transforming tightly bound excitons into weakly bound charge-transfer excitons and lowering the exciton binding energy, the system enables spontaneous exciton dissociation and more efficient utilization of photogenerated charges.
Enhanced internal electric field boosts charge migration
Compared with conventional supramolecular assemblies built from single-component molecular units, the hydrogen-bond-engineered interface and the strong donor-acceptor interactions in this composite generate a much stronger internal electric field. This enhanced field drives directional and faster charge migration within the photocatalyst. The researchers found that, after charge extraction and recombination, the effective surface hole population was increased by 6-fold compared with the non-hydrogen-bonded system. As a result, substantially more holes reach the catalyst surface, where they can directly participate in the water oxidation reaction, leading to markedly improved solar-to-oxygen conversion.
Breakthrough in oxygen evolution performance
The hydrogen-bonded photocatalyst delivers an exceptional oxygen evolution rate of 63.9 mmol g −1 h −1 under visible light, along with record apparent quantum efficiencies of 11.83% at 420 nm and 4.08% at even 650 nm. While most hydrogen-bond-based photocatalysts have focused on hydrogen evolution, hydrogen peroxide production, or CO 2 reduction, progress in the oxygen evolution reaction, the kinetically rate-determining step of overall water splitting, has remained limited. By achieving state-of-the-art oxygen evolution performance, this work identifies a promising hole-dominated semiconductor platform for constructing efficient overall water-splitting systems.
National Science Review
Experimental study