Incorporating p-Phenylene as an Electron-Donating Group into Graphitic Carbon Nitride for Efficient Charge Separation.

Low charge-separation transport efficiency resulting from structural defects largely limits photocatalytic hydrogen production over polymeric graphitic carbon nitride (PCN) photocatalyst. Herein, an electron-donating group, namely p-phenylene, is incorporated into PCN by a polycondensation reaction between carbon nitride and p-phenylenediamine (or p-benzoquinone) to repair the structural defects. The p-phenylene-modified PCN exhibits an almost fivefold increase in H ₂ evolution, a threefold increase in photocurrent density, and higher nonradiative rate (0.285 ns ^-1 ). Spectroscopic studies confirm that p-phenylene tends to bridge the heptazine-based oligomers through a polycondensation reaction. Theoretical calculations reveal that anchoring of the heptazine units by p-phenylene induces localization of h ⁺ and e ^- on the phenylene and melem moieties, respectively, which effectively separates the charge carriers. This strategy provides an opportunity to overcome structural defects in carbon nitride for efficient photocatalytic solar energy conversion.
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