4,4′,4″-Nitrilotribenzoic Acid/Graphitic Carbon Nitride Type II Heterostructures for Highly Efficient Photocatalytic Hydrogen Evolution from Water Splitting

Abstract

The metal-free polymer semiconductor pristine carbon nitride (CN) has garnered notable interest; however, its poor photocatalytic activity constrains its practical uses. Herein, we synthesize cost-effective, nonhazardous, boron (B)-doped graphitic carbon nitride (BCN) through thermal polymerization. The successful grafting of BCN with 4,4′,4″-nitrilotribenzoic acid (NBA) donor molecules via an amide covalent bond presents the construction of BCN-NBA type II heterostructures. This extended π-conjugated NBA electron donor loaded on BCN exhibits band gap enhancement with wideband optical absorbance in the visible range and augmented efficiency for the spatial charge separation and transport of photogenerated charges owing to the formation of type II heterojunction. The optimal BCN-NBA-3 photocatalyst shows enhanced H₂ production mobility with a rate of 208.67 μmol h^–1 at visible light illumination (λ ≥ 420 nm) with 1% Pt as cocatalyst and a high apparent quantum efficiency (AQE) of 8.16% at 450 nm monochromatic light. Compared with pure CN (10.67 μmol h^–1), about 19.56 folds higher H₂ evolution rate is observed for BCN-NBA-3 at visible light irradiation. Furthermore, the as-prepared photocatalyst displayed robust photocatalytic hydrogen generation for 16 h. This work emphasizes the possibility of using organic covalently functionalized CN to construct highly efficient heterostructured photocatalysts and opens up an avenue for practical applications in hydrogen production.