Barium- and Phosphorus-Codoped g-C₃N₄ Microtubes with Efficient Photocatalytic H₂ Evolution under Visible Light Irradiation

Abstract

Graphitic carbon nitride (CN) is a fascinating metal-free photocatalyst used to generate hydrogen utilizing solar energy directly, and its performance can be improved by tuning the electronic structure, enhancing the visible light absorbance via element doping, and increasing the surface active sites via nanostructure formation. Herein, porous Ba–P-codoped g-C3N4 microtubes (Ba–P–CN) with a large specific surface area are synthesized by calcined melamine, barium chloride, and hypophoaphoeous acid via a hydrothermal method. Ba–P-codoped g-C3N4 microtubes increase the specific surface area and visible light harvesting and narrow the band gap. Ba–P–CN exhibits enhanced photocatalytic performance, reaching H2 evolution rate up to 12.3 μmol/h under light λ > 420 nm, which is 13.2 times as high as that of CN. Experimental verification and theoretical calculation indicate that Ba and P doping increases the delocalized density of states distribution of highest occupied molecular orbitals and lowest unoccupied molecular orbitals and narrowed the band gap, and the formation of microtube structures augments the large specific surface area, in addition to improving the photocatalytic performance of g-C3N4.

Polymeric Carbon Nitride‐Derived Photocatalysts for Water Splitting and Nitrogen Fixation

“…Table 1 summarized the recent work on the PCN‐based photocatalysts, including their design strategies, applications, and properties. [ 57,114–156 ]…”

Recent Advances in g‐C3N4‐Based Photocatalysts for Pollutant Degradation and Bacterial Disinfection: Design Strategies, Mechanisms, and Applications

“…Reproduced with permission. [39] Copyright 2020, American Chemical Society. Reproduced with permission.…”

Graphitic carbon nitride nanotubes: a new material for emerging applications

“…A similar approach was applied to synthesize barium-and phosphorus-co-doped GCNTs starting from melamine and hypophosphorous acid. 140 A scrolling event stimulated by an ammonia ow through the melamine upon thermal condensation was suggested to be responsible for the formation of GCNTs during the calcination of close-packed melamine. 141 The melamine packing was achieved by shaking the crucible with a vibrator prior to the calcination, the latter yielding GCNT bunches with an inner tube diameter of 18 nm and a wall thickness of 15 nm.…”

“…The Ba-and P-co-doped GCNTs produced by scrolling were reported to be around 14 times more efficient photocatalysts of water splitting as compared to bulk GCN. 140 DFT calculations showed both dopants to contribute to the bandgap narrowing as well as to a higher delocalization of the GCN LUMO (Lowest Occupied Molecular Orbital) state thus increasing the efficiency of spatial separation of the photogenerated electrons and holes. 140 The GCNTs produced by shock-freezing induced rolling and modied by bimetallic Ag-Cu NCs 130 or Pt NCs 136 revealed a high photocatalytic activity in hydrogen evolution from aqueous solutions of sacricial donors (triethylamine, TEA, methanol), the efficiency of this process correlating with the oxidation potential of electron donors used.…”

“…140 DFT calculations showed both dopants to contribute to the bandgap narrowing as well as to a higher delocalization of the GCN LUMO (Lowest Occupied Molecular Orbital) state thus increasing the efficiency of spatial separation of the photogenerated electrons and holes. 140 The GCNTs produced by shock-freezing induced rolling and modied by bimetallic Ag-Cu NCs 130 or Pt NCs 136 revealed a high photocatalytic activity in hydrogen evolution from aqueous solutions of sacricial donors (triethylamine, TEA, methanol), the efficiency of this process correlating with the oxidation potential of electron donors used. 130 The photocatalytic water splitting process can be combined with the photocatalytic degradation of potentially dangerous water phenolic pollutants in systems based on GCNTs modied with Pt NCs.…”