Study on Photoelectrochemical Properties of Colorful Carbon Nitrides Synthesized in Liquid-Phase

Direct Photoelectric Storage of Solar Energy in C‐Rich Polymeric Carbon Nitride Cell: Mechanism and Performance Improvement

“…In addition, the 1 H NMR liquid-state spectra of the samples show the signals of H 2 O at 4.7 ppm and HN(C) 2 groups at 3.44 ppm as well as the characteristic two peaks for −CH 2 groups in citric acid from the residual reactants (Figure S3b, Supporting Information). The other four peaks assigned to different carbons in citric acid and the resonance at chemical shift of 57.4 ppm attributed to the sp 3 -bonded CN [21] are also visible on the 13 C liquid-state NMR spectra (Figure S3c, Supporting Information). The sp 3 -bonded CN can be the linkage group between heptazine motifs and aromatic nucleus.…”

“…The TEM image of the edge of the "sponge" shows the similar microstructure with the hollow spheres, i.e., thin wall-constructed nanonetworks (Figure 3c), which is highly desirable for energy storage applications. 13 C liquid-state nuclear magnetic resonance (NMR) spectra revealed the heptazine backbone structure of the samples synthesized with the molar ratio of dicyandiamide (C 2 H 4 N 4 ) to citric acid (C 6 H 7 O 8 ) varying from 1:0.15 to 1:1.31 (Figure 4a-g). Planar heptazine nucleus exhibits two characteristic signals.…”

“…The resonance at 164.6 ± 2.0 ppm results from the external heptazine carbons in C(e)N 2 (NH 2 ) groups and the one at 157.9 ± 2.0 ppm corresponds to the internal heptazine carbons (junctional, bonded to central nitrogen, and two nitrogens on the ring periphery) in the C(i)N 3 groups, [17,18] as shown in Figure 4h (right). A bunch of impurity peaks is visible on the 13 C NMR spectra of sample 1:0.15 and sample 1:0.22, resulting from bad polymerization of the samples. With the M C2H4N4 :M C6H8O7 ratio decreasing, the impurity peaks disappeared.…”

“…The 13 C NMR signals for conjugated carbon frameworks exhibit in the chemical shifts ranging from 100 to 150 ppm. [19] The chemical shifts of 121.8 ± 2.0 ppm can be attributed to the edge CH carbons and 137.6 ± 2.0, 129.8 ± 2.0, 126.4 ± 2.0 ppm can be assigned to three quaternary interior carbons, respectively, [20] as shown in Figure 4h (left).…”

“…[11] Meanwhile, we reported a carbon-rich polymeric carbon nitrides (CPCN) with a band gap of 1.74 eV thus strong visible light absorption, which served as the photoelectrode in a photoelectrochemical (PEC) solar cell and successfully demonstrated direct solar-to-electric energy conversion and storage. [12,13] 2D carbon-rich conjugated polymer frameworks have drawn growing research interest as a new generation of multifunctional materials. Typical carbonrich conjugated polymer frameworks are characterized by layerstacked periodic structure with high in-plane π-conjugation.…”