Applied Catalysis B: Environmental, Vol.248, 84-94, 2019
Unveiling the origin of boosted photocatalytic hydrogen evolution in simultaneously (S, P, O)-Codoped and exfoliated ultrathin g-C3N4 nanosheets
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-C(3)N(4)can be simultaneously co-doped with S, P and O nonmetal-atoms and exfoliated into ultrathin 2D nanosheets with a thickness of similar to 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 H-2 evolution rate reaching 2480 mu mol g(-1) h(-1). First-principle calculations and experimental evidences suggest that, upon elemental doping within the g-C(3)N(4 )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 H-2 production. Importantly, the in-situ generated 2D g-C3N4 nanosheets exhibited more catalytic surface sites, which was highly beneficial to the photocatalytic water splitting.