Segmented Structure Design of Carbon Ring In-Plane Embedded in g-C 3 N 4 Nanotubes for Ultra-High Hydrogen Production.

The photocatalytic water splitting capability of metal-free graphitic carbon nitride (g-C 3 N 4 ) photocatalyst is determined by its microstructure and photoexcited electrons transfer. Herein, a segmented structure was developed, consisting of alternant g-C 3 N 4 nanotubes and graphitic carbon rings (denoted as C r -CN-NT). The C r -CN-NT showed ordered structure and ultralong length/diameter ratio of 150 nm in diameter and a few microns in lengths, which promoted electron transport kinetics and elongated photocarrier diffusion length and lifetime. Meanwhile, the local in-plane π-conjugation was formed and extended in C r -CN-NT, which could improve charge carrier density and prohibit electron-hole recombination. Accordingly, the average hydrogen evolution rate of C r -CN-NT reached 9245 μmol h -1  g -1 , which was 61.6 times that of pristine CN, and the remarkable apparent quantum efficiency (AQE) of C r -CN-NT reached up to 12.86 % at 420 nm. This work may provide a pathway for simultaneous morphology regulation and in-plane modification of high-performance photocatalysts.