Enhanced electron density of the π-conjugated structure and in-plane charge transport to boost photocatalytic H2 evolution of g-C3N4

• Published in: Science China materials 2023-06, Vol.66 (6), p.2274-2282
• Main Authors: Zhang, Yang, Cao, Ning, Liu, Xiaoming, He, Fengting, Zheng, Bin, Zhao, Chaocheng, Wang, Yongqiang
• Format: Article
• Language: English
• Subjects: Ammonium oxalate monohydrate; Carbon nitride; Catalytic activity; Charge transport; Chemistry and Materials Science; Chemistry/Food Science; Condensation polymerization; Electron density; Electron paramagnetic resonance; Heat treatment; Hydrogen evolution; Hydrogen reduction; Materials Science; NMR; Nuclear magnetic resonance; Photocatalysis
• ISSN: 2095-8226; 2199-4501
• DOI: 10.1007/s40843-022-2345-1

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.