Template-free preparation of carbon nitride hollow spheres with adjustable sizes for photocatalytic hydrogen generation.

ABSTRACT

Carbon nitride hollow spheres (CNHS) with adjustable sizes were successfully fabricated via a template-free supramolecular pre-assembly strategy, in which melamine-cyanuric acid (MCA) hollow spheres were constructed through hydrogen bonds. A feasible formation mechanism was proposed, which coupled an inside-out Ostwald ripening with the supramolecular pre-assembly process. Interestingly, the sizes of MCA could be manipulated by changing the pre-assembly temperature. Consequently, the sizes of CNHS were adjustable. The optimal CNHS exhibited excellent photocatalytic hydrogen evolution rate (98.6 µmol/h) in the visible-light region, which was approximately 11 times higher than that of bulk carbon nitride calcined by melamine. The significantly improved performance was due to the contributions including the unique architectures with remarkable light absorption ability, high electrical conductivity, relatively narrowed band gap, fast charge separation. This work provides a facile template-free supramolecular pre-assembly strategy to fabricate carbon nitride hollow spheres with adjustable sizes for the first time.