Accurate engineering of hexagonal hollow carbon nitride with carbon vacancies: enhanced photocatalytic H2 evolution and its mechanism

Abstract

Vacancy engineering and morphology construction were integrated simultaneously by the self-assembly of melamine (MA) and cyanuric acid (CA) in the presence of P123 and H₂SO₄, which contributed to the hexagonal hollow carbon nitride with carbon vacancies (HHCN). P123 functioned as the structure directing agent and H₂SO₄ acted as the hole-maker and stability-maintainer, the synergistic effect of whom contributed to the hexagonal hollow structure. Meanwhile, the chemical oxidation etching of H₂SO₄ brought about carbon vacancies. Combined with experiments and DFT calculations, it was found that carbon vacancy improved the separation rate of photo-induced carriers as well as the adsorption capacity of reaction substrate (H₂O molecules) and negatively shifted the CB potential. Therefore, HHCN was endowed with the superior photocatalytic hydrogen evolution rate (5140 μmol h⁻¹ g⁻¹), which was 18.3-fold higher than g-C₃N₄. Furthermore, the possible formation mechanism and photocatalytic mechanism were proposed. This work offered an excellent basis for vacancy engineering and morphology construction for the modification of carbon nitride.