Electronic and energy level structural engineering of graphitic carbon nitride nanotubes with B and S co-doping for photocatalytic hydrogen evolution

The ideal photocatalyst used for photocatalytic water splitting requires strong light absorption, fast charge separation/transfer ability and abundant active sites. Heteroatom doping offers a promising and rational approach to optimize the photocatalytic activity. However, achieving high photocatalytic performance remains challenging if just relying on single-element doping. Herein, Boron (B) and sulfur (S) dopants are simultaneously introduced into graphitic carbon nitride (g-C3N4) nanotubes by supramolecular self-assembly strategy. The developed B and S co-doped g-C3N4 nanotubes (B,S-TCN) exhibited an outstanding photocatalytic performance in the conversion of H2O into H-2 (9.321 mmol g(-1)h(-1)), and the corresponding external quantum efficiency (EQE) reached 5.3% under the irradiation of lambda = 420 nm. It is well evidenced by the closely combined experimental and (density functional theory) DFT calculations: (1) the introduction of B dopants can facilitate H2O adsorption and drive interatomic electron transfer, leading to efficient water splitting reaction. (2) S dopants can stretch the VB position to promote the oxidation ability of g-C3N4, which can accelerate the consumption of holes and thus inhibit the recombination with electrons. (3) the simultaneous introduction of B and S can engineer the electronic and energy level structural of g-C3N4 for optimizing interior charge transfer. Finally, the purpose of maximizing photocatalytic performance is achieved.

Automated summary

The ideal photocatalyst for photocatalytic water splitting should have strong light absorption, fast charge separation/transfer ability, and abundant active sites. Heteroatom doping offers a promising approach for optimizing photocatalytic activity. In this study, boron (B) and sulfur (S) dopants were simultaneously introduced into graphitic carbon nitride (g-C3N4) nanotubes using a supramolecular self-assembly strategy. The developed B and S co-doped g-C3N4 nanotubes exhibited outstanding photocatalytic performance, achieving a conversion rate of H2O to H-2 of 9.321 mmol g(-1)h(-1), with an external quantum efficiency of 5.3% under irradiation at λ = 420 nm. The introduction of B dopants facilitated H2O adsorption and interatomic electron transfer, while S dopants promoted the oxidation ability of g-C3N4 and inhibited recombination. Furthermore, the simultaneous introduction of B and S optimized the electronic and energy level structures of g-C3N4 for efficient charge transfer, ultimately maximizing photocatalytic performance.