g-C3N4 nanorods modified with N defects via the molten salt method: efficient photocatalysts for hydrogen production

Abstract

Owing to the intrinsic limitations of g-C₃N₄, its photocatalytic performance is less than optimal. To overcome this, the modification process of g-C₃N₄ was designed through a molten salt method to achieve a nanorod morphology and introduce N defects (CN-PS, CN-PC, and CN-SS). During the process, the alkali metal salt not only promoted the introduction of N1 vacancies at a low synthesis temperature as a solid solvent and introduced an additional cyano group (–CN) into the CN-SS but also acted as a morphology guide agent to transform the modified catalyst into a nanorod morphology. The nanorod morphology provided a one-dimensional pathway for charge migration, and the N defect enhanced the photocatalytic activity while regulating the band structure. The morphological control and defect engineering endowed modified catalysts with enhanced hydrogen evolution performance. Notably, the CN-SS nanorods with N1 vacancy and –CN exhibited an excellent photocatalytic H₂ evolution rate of 0.74 mmol g⁻¹ h⁻¹ for photocatalytic water splitting (PWS), and it increased up to 3.51 mmol g⁻¹ h⁻¹ upon addition of 0.5 vol% TEOA as a sacrificial agent under visible light. This study proves the positive influence of morphology control and defect engineering on improving the catalytic performance of g-C₃N₄.