A facile mechanochemical route to a covalently bonded graphitic carbon nitride (g-C3N4) and fullerene hybrid toward enhanced visible light photocatalytic hydrogen production

Graphitic carbon nitride (g-C₃N₄) as an emerging two-dimensional (2D) nanomaterial has been commonly used as a metal-free photocatalyst with potential applications in visible light photocatalytic water-splitting. However, the photocatalytic activity of g-C₃N₄ is quite low due to its relatively large band gap and the existence of contact resistance between the nanosheets. Herein we report for the first time the facile synthesis of a covalently bonded g-C₃N₄/C₆₀ hybrid via a solid-state mechanochemical route and its application in photocatalytic hydrogen production under visible light. The g-C₃N₄/C₆₀ hybrid was synthesized by ball-milling g-C₃N₄ and C₆₀ in the presence of lithium hydroxide (LiOH) as a catalyst. The hybrid nature and conformation of the g-C₃N₄/C₆₀ hybrid were confirmed by a series of spectroscopic and morphological studies, featuring the covalent bonding of C₆₀ onto the edges of g-C₃N₄ nanosheets via a four-membered ring of azetidine, which has never been reported in fullerene chemistry. The g-C₃N₄/C₆₀ hybrid was further applied to metal-free visible light photocatalytic hydrogen production, affording a H₂ production rate of 266 μmol h^-1 g^-1 without using any noble metal cocatalyst such as Pt, which is about 4.0 times higher than that obtained for the pristine g-C₃N₄ photocatalyst.