Ammonia-induced robust photocatalytic hydrogen evolution of graphitic carbon nitride

Abstract

We report a new and effective method to prepare high activity graphitic carbon nitride (g-C3N4) by a simple ammonia etching treatment. The obtained g-C3N4 displays a high BET surface area and enhanced electron/hole separation efficiency. The hydrogen evolution rates improved from 52 μmol h(-1) to 316.7 μmol h(-1) under visible light.

Reduced Oxygenated g‐C3N4 with Abundant Nitrogen Vacancies for Visible‐Light Photocatalytic Applications

“…Accordingly, the effective separation of photogenerated carriers should benefit the photocatalytic performance of RCNO and possibly lead to a higher photocatalytic activity with respect to the degradation of AO7. The time‐resolved PL spectra was used to examine the lifetime of photogenerated charge carriers (Figure b). Accordingly, RCNO and g ‐C 3 N 4 exhibited biexponential decay characteristics, of which the fluorescent decay of RCNO was obviously slower than that of raw g ‐C 3 N 4 .…”

“…Accordingly,t he effective separation of photogenerated carriers should benefitt he photocatalytic performance of RCNO and possibly lead to ah igher photocatalytic activity with respectt ot he degradation of AO7. The time-resolved PL spectra was used to examine the lifetime of photogenerated chargec arriers [37] (Figure 6b). Accordingly, RCNO and g-C 3 N 4 exhibited biexponential decay characteristics, of whicht he fluorescentd ecay of RCNO was obviously slower than that of raw g-C 3 N 4 .Ass hown in Figure 6b,t he fluorescent lifetimes t 1 and t 2 increased from 1.16 and 4.91 ns for g-C 3 N 4 to 1.32 and 5.91 ns for RCNO, whereas the relative contribution of the slower decay component (I 2 )i ncreasedf rom 56 to 64 %.…”

Defective graphitic carbon nitride synthesized by controllable co-polymerization with enhanced visible light photocatalytic hydrogen evolution

“…As shown in Figure 6b, with the increasing size of capping groups, the bandgap gradually changes from 2.73 to 2.66 eV. The narrowing of optical absorption can be ascribed to the appearance of nitrogen vacancies, 21 especially for CN-DPT. Our present work is similar to the previous report on black TiO 2 , which concluded that the shrinking of band gap was resulted from the substantial oxygen vacancies introduced by hydrogen treatment.…”

“…Not surprisingly that CN-DPT exhibits the highest hydrogen evolution rate of about 69.9 μmol h −1 , which is 10 times higher than g-C 3 N 4 (about 7.00 μmol h −1 ), and more efficient than former described defective g-C 3 N 4 produced by H 2 or NH 3 treatment. 20,21 Figure S6 shows that the effects of different ratio on the photocatalytic activities of these monomers. When the proportion of these monomers is at 1 to 10, all modified g-C 3 N 4 (CN-DT, CN-DMT, and CN-DPT) show the best photocatalytic activities.…”

“…19,20 In another recent study, Yang reported a NH 3 etching treatment to produce defective g-C 3 N 4 with high specific surface and porous, the hydrogen evolution increased 6 times under visible light. 21 However, these methods usually involve relatively complicated and unsafe processes, and the product yields are rather low as well.…”