In a recent decade, graphitic carbon nitride has emerged as a promising engineered nanomaterial with excellent visible light photoreactivity, outstanding stability, remarkable biocompatibility, and affordable costs. Graphitic carbon nitride has found broad applications in environmental remediation, energy storage, sensing, biomedical engineering and membrane separation. With potential commercialization and increasing usage in the future, graphitic carbon nitride can pollute the environment during manufacturing, in applications, and after inappropriate disposal. Knowledge about the transformation of graphitic carbon nitride in engineering settings, and natural or built environments is essential to assess material robustness in use and environmental risks. Only hydroxyl radicals were believed to be responsible for graphitic carbon nitride decomposition before, but our recent study has demonstrated that photoinduced holes on the material significantly enhance material decomposition under hydroxyl radicals attack, by using an integrated experimental and simulation approach. In the dark, hydroxyl radicals only break a limited amount of C-N bonds connecting edge-site heptazine units and tear heptazine units apart from edges of the graphitic carbon nitride nanosheet, resulting in peripheral etching and slow degradation. In contrast, photoinduced holes decrease the activation energy barrier of C-N bond breaking between heptazines, and hydroxyl radicals thus oxidize graphitic carbon nitride and release heptazine units from the entire nanosheet. The degradation pathway shifts to bulk fragmentation, leading to much faster degradation. This discovery not only provides guidelines for designing safe and robust nanomaterials but also sheds light on understanding the unique environmental transformation and fate of emerging photoreactive nanomaterials.

Radical-driven decomposition of graphitic carbon nitride: light exposure matters

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.