Fragmented phosphorus-doped graphitic carbon nitride nanoflakes with broad sub-bandgap absorption for highly efficient visible-light photocatalytic hydrogen evolution

• Published in: Applied catalysis. B, Environmental Environmental, 2018-06, Vol.225, p.397-405
• Main Authors: Fang, Hua-Bin, Zhang, Xiao-Hong, Wu, Jiaojiao, Li, Nan, Zheng, Yan-Zhen, Tao, Xia
• Format: Article
• Language: English
• Subjects: Absorption; Carbon nitride; Catalytic activity; Charge transfer; Doping; Electromagnetic absorption; Energy conversion; Fragmentation; Fragmented nanoflakes; g-C3N4; Hydrogen; Hydrogen evolution; Hydrogen production; Hydrogen storage; Migration; Phosphorus; Phosphorus doping; Photocatalysis; Phytic acid; Recombination; Solar energy; Sub-bandgap; Surface area; Surface charge; Surface chemistry; Synergistic effect; Urea; Valence band; Visible-light-driven H2 evolution
• ISSN: 0926-3373; 1873-3883
• DOI: 10.1016/j.apcatb.2017.11.080

[Display omitted] •Fragmented P-doped g-C3N4 nanoflakes are prepared by a facile two-step processing.•PCNNFs show broad sub-bandgap absorption extending light absorption up to 800 nm.•The resultant PCNNFs show much enlarged surface area.•PCNNFs are demonstrated to be highly efficient in charge transfer and separation.•PCNNFs exhibit remarkable visible light photocatalytic H2 production activity. Graphitic carbon nitride (g-C3N4) has shown great promise in photocatalytic solar-energy conversion. However, photocatalytic activity of pristine g-C3N4 still remains restricted owing to its low surface area, insufficient visible-light harvesting, and ready charge recombination. Here, fragmented P-doped g-C3N4 nanoflakes (PCNNFs), which are prepared by a facile two-step processing combining P-doping via using phytic acid biomass as P source and urea as g-C3N4 precursor and nanostructure tailoring via a smart post-treatment, are reported. Particularly, PCNNFs exhibit narrowed sub-bandgap from valence band to the midgap states, extending light absorption up to 800 nm. The resultant PCNNFs sample shows a surface area of 223.2 m2 g−1, a highest value of P-doped g-C3N4 reported. The fragmented nanoflakes structure renders PCNNFs much shortened charge-to-surface migration distance in both vertical-plane and in-plane direction. Such PCNNFs are demonstrated to be highly efficient in charge transfer and separation. Attributed to the synergistic effect of P-doping and fragmented nanoflakes structure, PCNNFs exhibit a remarkable visible-light (>420 nm) photocatalytic H2 production rate of 15921 μmol h−1 g−1 and quantum efficiencies of 6.74% at 420 nm and 0.24% at 600 nm. Moreover, even under long wavelength light (>470 nm), PCNNFs still exhibit high H2 production rate of 9546 μmol h−1 g−1, over 62 times the rate of pure g-C3N4.