Unveiling the origin of boosted photocatalytic hydrogen evolution in simultaneously (S, P, O)-Codoped and exfoliated ultrathin g-C3N4 nanosheets

• Published in: Applied catalysis. B, Environmental Vol. 248; pp. 84 - 94
• Main Authors: Liu, Qinqin, Shen, Jiyou, Yu, Xiaohui, Yang, Xiaofei, Liu, Wei, Yang, Juan, Tang, Hua, Xu, Hui, Li, Huaming, Li, Youyong, Xu, Jingsan
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 05.07.2019; Elsevier BV
• Subjects: 2D materials; Atomic properties; Carbon nitride; Catalysis; Charge transfer; Conduction; Conduction bands; Doping; Electromagnetic absorption; First principles; g-C3N4; Hydrogen; Hydrogen evolution; Hydrogen production; Light; Nanosheets; Nanostructure; Nonmetal co-doping; Photocatalysis; Photocatalytic hydrogen evolution; Thickness; Water splitting; g-C3N4; Photocatalytic hydrogen evolution; Nonmetal co-doping; 2D materials
• ISSN: 0926-3373; 1873-3883
• DOI: 10.1016/j.apcatb.2019.02.020

[Display omitted] •S,P,O-codoped ultrathin 2D g-C3N4 nanosheets were successfully fabricated.•The 2D g-C3N4 photocatalyst demonstrates highly improved HER performance.•2D nanosheet structure and efficient charge transfer accelerate HER efficiency.•DFT reveals heteroatom doping boosts the charge separation and transport in g-C3N4 framework. Recently, metal-free graphitic carbon nitride (g-C3N4) has been recognized as a potential candidate for high-performance photocatalytic hydrogen production while challenges still remain due to poor electronic properties and limited surface active sites. We demonstrate that g-C3N4 can be simultaneously co-doped with S, P and O nonmetal-atoms and exfoliated into ultrathin 2D nanosheets with a thickness of ∼3 nm by a simple, sequential thermal synthesis. The multi-atoms doping and nanostructure modulation remarkably enhanced the photocatalytic hydrogen production under illumination, with the optimal H2 evolution rate reaching 2480 μmol g−1 h−1. First-principle calculations and experimental evidences suggest that, upon elemental doping within the g-C3N4 framework, S atoms occupied the interstitial sites and P and O atoms replaced the C and N atoms, respectively. Consequently, photo-induced charge transfer and separation significantly improved owing to the construction of a more favorable charge transfer pathway. Furthermore, introducing heteroatoms into the structure of g-C3N4 narrowed the bandgap and negatively shifted the conduction band edge, leading to extended visible-light absorption and stronger electron reducibility for subsequent H2 production. Importantly, the in-situ generated 2D g-C3N4 nanosheets exhibited more catalytic surface sites, which was highly beneficial to the photocatalytic water splitting.