Molecule Self-Assembly Synthesis of Porous Few-Layer Carbon Nitride for Highly Efficient Photoredox Catalysis

Abstract

Polymeric carbon nitride (C3N4) has emerged as the most promising candidate for metal-free photocatalysts but is plagued by low activity due to the poor quantum efficiency and low specific surface area. Exfoliation of bulk crystals into ultrathin nanosheets has proven to be an effective and widely used strategy for enabling high photocatalytic performances; however, this process is complicated, time-consuming, and costly. Here, we report a simple bottom-up method to synthesize porous few-layer C3N4, which involves molecule self-assembly into layered precursors, alcohol molecules intercalation, and subsequent thermal-induced exfoliation and polycondensation. The as-prepared few-layer C3N4 expose more active sites and greatly enhance the separation of charge carriers, thus exhibiting a 26-fold higher hydrogen evolution activity than bulk counterpart. Furthermore, we find that both the high activity and selectivity for the oxidative coupling of amines to imines can be obtained under visible light that surpass those of other metal-free photocatalysts so far.

Short‐time Thermal Oxidation of Ultrathin and Broadband Carbon Nitride for Efficient Photocatalytic H2 Generation

“…Two diffraction peaks at 13.1° and 27.3° are attributed to the (100) plane for in‐plane repeated units of tri‐s‐triazine and the (002) plane for interlayer packing of CN, respectively . Compared to Bulk CN and BCN, two diffraction peaks of UCN and UBCN both become much weaker, which may be due to the successful exfoliation of ultrathin structure during the second calcination process . Structural information of the synthesized CN samples can be further confirmed by FT‐IR spectra in Figure b, the characteristic absorption bands of all the CN samples show no significant change, demonstrating that the typical CN structure is well maintained .…”

“…[15] Compared to Bulk CN and BCN, two diffraction peaks of UCN and UBCN both become much weaker, which may be due to the successful exfoliation of ultrathin structure during the second calcination process. [13,16] Structural information of the synthesized CN samples can be further confirmed by FT-IR spectra in Figure 3b, the characteristic absorption bands of all the CN samples show no significant change, demonstrating that the typical CN structure is well maintained. [10a,17] Meanwhile, the surface 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 composition and chemical state of UBCN were determined by XPS analysis (Figure 4).…”

“…When compared to Bulk CN and BCN, both UCN and UBCN are exfoliated into ultrathin structure successfully (Figure d, 1e, 1 h and 1i), which indicates that the specific surface areas of UCN and UBCN are larger than that of Bulk CN and BCN. In addition, UBCN retains the highly porous structure of BCN, which is not available for UCN, the highly porous structure can shorten the diffusion path for photogenerated carriers and enhance the absorption of reactants . According to the atomic force microscopy (AFM) images (Figure ), the measured thickness of Bulk CN is about 230 nm, and the thickness of UBCN is exfoliate to about 1.37 nm, revealing that UBCN has a ultrathin structure .…”

“…In addition, UBCN retains the highly porous structure of BCN, which is not available for UCN, the highly porous structure can shorten the diffusion path for photogenerated carriers and enhance the absorption of reactants. [13] According to the atomic force microscopy (AFM) images (Figure 2), the measured thickness of Bulk CN is about 230 nm, and the thickness of UBCN is exfoliate to about 1.37 nm, revealing that UBCN has a ultrathin structure. [14] The larger specific surface area and the abundant porous structure can be further validated by Nitrogen adsorption-desorption isotherms and Pore size distribution curves.…”

Formation of g‐C3N4 Nanotubes towards Superior Photocatalysis Performance

“…Thinning treatment for g‐C 3 N 4 using ultra‐sonication is the first idea to reduce the recombination of photogenerated electrons and holes . Zhu et al.…”