Efficient exciton dissociation in polymeric photocatalysts for hot-electron-involved photocatalytic performance

  • Recently, research group from University of Science and Technology of China led by Prof. Yi Xie got new progress in excitonic research of polymeric photocatalysts. They found that dramatic hot-carrier generation could be realized in semicrystalline polymeric photocatalysts, undergoing an efficient exciton dissociation process at the order–disorder interfaces, which would dramatically facilitate the hot-carrier-involved photocatalytic reactions. The work has been published as an article in Journal of American Chemical Society (J. Am. Chem. Soc., DOI: 10.1021/jacs.6b12878).

    Photocatalysis, a typical photoexcitation process that has been widely studied for its potential in solving energy crisis and environmental pollution, is traditionally believed to be related to the photogenerated hot carriers, whereas the potential excitonic effects of photocatalysts arising from the Coulomb interactions between photogenerated electrons and holes have rarely been realized. Herein, by taking polymeric heptazine-based melon (nominally, polymeric carbon nitride) as an example, the researchers demonstrate that accelerated exciton dissociation at order–disorder interfaces would be an alternative strategy for achieving promoted hot-carrier-involved photocatalytic performance.

    Theoretical simulations suggest that intriguing charge carrier behavior would accompany with exciton dissociation, where electron-injection towards ordered chains and hole-blocking in disordered chains would selectively facilitate hot-electron harvesting. Experimental results show the lower exciton concentrations and fast exciton decay in semicrystalline samples, suggesting the positive influence of order–disorder interfaces towards exciton dissociation in polymeric catalysts. Moreover, electrochemical tests indicate semicrystalline sample showed a ~7-fold electron concentration promotion and ~5-fold photocurrent enhancement with respect to its pristine counterpart. Benefiting from these notable enhancements, semicrystalline heptazine-based melon exhibits excellent performances in hot electron involved photocatalytic processes, such as superoxide radical production and selective alcohol oxidation.

    This work offers an in-depth understanding on excitonic aspects of photoexcitation process in polymeric photocatalysts, which would provide instructive guidance for improving hot-carrier-involved photocatalytic quantum efficiency.

    (School of Chemistry and Materials Science)

    Publication link: http://pubs.acs.org/doi/abs/10.1021/jacs.6b12878