4,4′,4″-Nitrilotribenzoic\nAcid/Graphitic\nCarbon Nitride Type II Heterostructures for Highly Efficient Photocatalytic\nHydrogen Evolution from Water Splitting

The metal-free polymer semiconductor\npristine carbon nitride (CN)\nhas garnered notable interest; however, its poor photocatalytic activity\nconstrains its practical uses. Herein, we synthesize cost-effective,\nnonhazardous, boron (B)-doped graphitic carbon nitride (BCN) through\nthermal polymerization. The successful grafting of BCN with 4,4′,4″-nitrilotribenzoic acid (NBA) donor\nmolecules via an amide covalent bond presents the construction of\nBCN-NBA type II heterostructures. This extended π-conjugated\nNBA electron donor loaded on BCN exhibits band gap enhancement with\nwideband optical absorbance in the visible range and augmented efficiency\nfor the spatial charge separation and transport of photogenerated\ncharges owing to the formation of type II heterojunction. The optimal\nBCN-NBA-3 photocatalyst shows enhanced H<sub>2</sub> production mobility\nwith a rate of 208.67 μmol h<sup>–1</sup> at visible\nlight illumination (λ ≥ 420 nm) with 1% Pt as cocatalyst\nand a high apparent quantum efficiency (AQE) of 8.16% at 450 nm monochromatic\nlight. Compared with pure CN (10.67 μmol h<sup>–1</sup>), about 19.56 folds higher H<sub>2</sub> evolution rate is observed\nfor BCN-NBA-3 at visible light irradiation. Furthermore, the as-prepared\nphotocatalyst displayed robust photocatalytic hydrogen generation\nfor 16 h. This work emphasizes the possibility of using organic covalently\nfunctionalized CN to construct highly efficient heterostructured photocatalysts\nand opens up an avenue for practical applications in hydrogen production.