Chongbei Wu,Guanhang Yu,Yue Yin,Yuze Wang,Li Chen,Qing Han,Junwang Tang,Bo Wang
Conjugated polymers are promising light harvesters for water reduction/oxidation due to their simple synthesis and adjustable bandgap. Herein, both cyanamide and triazole functional groups are first incorporated into a heptazine-based carbon nitride (CN) polymer, resulting in a mesoporous conjugated cyanamide-triazole-heptazine polymer (CTHP) with different compositions by increasing the quantity of cyanamide/triazole units in the CN backbone. Varying the compositions of CTHP modulates its electronic structures, mesoporous morphologies, and redox energies, resulting in a significantly improved photocatalytic performance for both H 2 and O 2 evolution under visible light irradiation. A remarkable H 2 evolution rate of 12723 µmol h −1 g −1 is observed, resulting in a high apparent quantum yield of 11.97% at 400 nm. In parallel, the optimized photocatalyst also exhibits an O 2 evolution rate of 221 µmol h −1 g −1 , 9.6 times higher than the CN counterpart, with the value being the highest among the reported CN-based bifunctional photocatalysts. This work provides an efficient molecular engineering approach for the rational design of functional polymeric photocatalysts.
Graphite carbon nitride (g-C 3 N 4 ) has become an emerging metal-free photocatalyst and attracted the attention of researchers. However, pure g-C 3 N 4 (PCN) prepared by traditional thermal condensation polymerization has a low polymerization of heptazine ring chains and a large number of charge recombination centers, which hinder in-plane charge transport, leading to undesirable photocatalytic performance. Herein, PCN fabrication by thermal treatment with ammonium oxalate monohydrate was performed to produce highly dispersed porous g-C 3 N 4 nanosheets, and the integrity of their in-plane heptazine ring chains was successfully improved without introducing heteroatoms. Electron paramagnetic resonance and 13 C nuclear magnetic resonance analyses revealed significantly increased electron density and delocalization of the π-conjugated structure. The obtained samples exhibited acceptable stability and photocatalytic activity, and the hydrogen reduction rates without and with the Pt co-catalyst were 11.2 and 5.3 times that of PCN.
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