Carboxyl functionalized graphite carbon nitride for remarkably enhanced photocatalytic hydrogen evolution

Graphitic carbon nitride (g-C3N4) has recently emerged as a promising candidate for photocatalytic hydrogen evolution, but only showed limited activity owing to its sluggish photogenerated carriers separation and migration. Herein, the carboxyl-functionalized g-C3N4 (OCN) was synthesized by a grafting post-treatment method to alleviate the negative influences from this intrinsic drawback. As a result, the surface carboxyl groups greatly improve charge carrier dynamics to suppress carriers recombination via the driving force originated from its electron-withdrawing effects. The resultant OCN exhibits 52 times higher hydrogen evolution rate than the pristine, and possesses a high apparent quantum yield (AQY) of 15.7 % at 420 ± 15 nm. This work deepens the understanding of the surface group related modifications for photocatalytic materials, further providing a promising approach for rational design of photocatalysts with highly efficient solar energy conversion.