Graphitic Carbon Nitride Modified with 1,3-Benzothiazole-2-carbaldehyde for Enhancement of Visible Light Hydrogen Production Activity

The utilization of clean energy is being explored to address energy and environmental challenges, with hydrogen emerging as a promising next-generation energy source. Research efforts are focused on hydrogen production through water splitting using graphitic carbon nitride (g-C₃N₄), a polymer semiconductor photocatalyst. In this process, a photocatalyst-dispersed aqueous solution is irradiated with light to generate hydrogen. g-C₃N₄ is characterized by its non-toxic nature, thermal and physical stability, and favorable bandgap [1]. However, its low specific surface area, limited light absorption range, and high photogenerated electron--hole recombination rate hinder its photocatalytic efficiency [2]. In this study, 1,3-benzothiazole-2-carbaldehyde is introduced into g-C₃N₄ to enhance the intramolecular charge transfer, thereby improving hydrogen production activity.

The photocatalyst was synthesized by the triple calcination of dicyanodiamide and 1,3-benzothiazole-2-carbaldehyde. Photocatalytic activity was evaluated by adding triethanolamine (sacrificial agent) and hexachloroplatinic acid to the catalyst in an aqueous solution, purging with nitrogen, and irradiating with visible light (λ ≥ 420 nm) for 6 h. Hydrogen production was quantified by gas chromatography (GC/TCD). The crystal structure, morphology, surface state, and optical properties of the photocatalysts were also characterized.

The optimized g-C₃N₄ modified with 1,3-benzothiazole-2-carbaldehyde demonstrated a hydrogen generation rate of 690 µmol h-1 g-1 through photocatalysis. This rate was roughly 14 times higher than that observed for unmodified g-C₃N₄. The characterization results showed that the benzothiazole-doped g-C₃N₄ exhibited exfoliation of the nanosheets and changes in surface structure. Additionally, a low fluorescence intensity and an extended visible light absorption range were observed. These effects were attributed to the introduction of 1,3-benzothiazole-2-carbaldehyde, which formed a donor--acceptor structure, enhancing the separation and transfer of photogenerated carriers. Consequently, the number of reactive electrons increased, leading to improved hydrogen production activity.

REFERENCES

[1] X. Zhang, F. Wu, G. Li, L. Wang, J. Huang, A. Song, A. Meng, Z. Li, Journal of Colloid and Interface Science, 655, 2024, 439-450

[2] F. Zhou, X. Chen, Y. Zhao, J. Cheng, G. Xu, Journal of Photochemistry & Photobiology, A: Chemistry, 449, 2024, 115378.