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Abstract
Carbon nitride semiconductors are strong candidates for visible light photocatalysts, but the increased Coulombic forces of the singlet Frenkel excitons lead to a narrowed bandgap and weakened exciton dissociation. We overcome this contradiction by co-injecting π-rich electronic domains and polarizable hydroxyl units into mesoporous carbon nitride, achieved through solution thermal shock. The embedded delocalized π-conjugated aromatic domains derived from non-conjugated macromolecules lower the conduction band edge and facilitate spatial separation of photogenerated electrons in the lowest unoccupied molecular orbital and holes in the highest occupied molecular orbital. Meanwhile, the polarizable hydroxyls can induce different electrons to flow from the triazine backbone to peripheral positions, enhancing water adsorption and proton reduction capability. Consequently, the polymeric carbon nitride exhibits an enhanced hydrogen evolution rate, 17.5 times higher than that of urea thermally treated through traditional strategies. These results suggest that our strategy can inject different functional motifs into carbon nitride, thereby improving photocatalytic activity.
Key Points of the Full Text
Point One: This article reports on the solution thermal shock method that suppresses irreversible phase separation between monomers with lattice mismatches and different starting/platform pyrolysis temperatures, effectively injecting π-rich electronic motifs into carbon nitride based on non-conjugated molecules. The prepared carbon nitride also features mesoporous ultrathin nanosheets with abundant folds and polarizable hydroxyls.
Point Two: The chemical composition and geometric features of carbon nitride give it a wide optical absorption range, extending into the near-infrared region, enhancing charge separation capability and improving hydrophilicity, thereby overcoming the limitations of low exciton dissociation due to increased Coulombic forces from a smaller bandgap. Therefore, under visible light irradiation (λ>420 nm), the prepared carbon nitride exhibits significant photocatalytic hydrogen evolution activity, with a hydrogen production rate more than 17.5 times higher than that of urea thermally treated products prepared by traditional methods.
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DOI: 10.1021/acsnano.2c0864
Proofread by: Liu Pingping