Embedded carbon in a carbon nitride hollow sphere for enhanced charge separation and photocatalytic water splitting.

Surface modification and morphological engineering are two important approaches to improve photocatalysis through enhancing photoabsorption and retarding charge recombination. Herein, a graphitic carbon integrated graphitic carbon nitride (C3N4) hollow sphere has been prepared via the modified shape-selective templating method in order to enchance light absorption and promote charge seperation under visible-light irradiation. MCM-41 that underwent carbonization at different temperatures in an inert atmosphere but not the conventional soft-template elimination was utilized as the sacrificial template. The resultant materials achieved an excellent photocatalytic performance with their hydrogen evolution rate reaching 718.1 μmol g-1 h-1, approximately 15 times higher than that of the bulk graphitic C3N4, resulting in 1.54% apparent quantum yield at 420 nm. The efficient photocatalysis was mainly attributed to the synergy of the vesicle morphology and carbon modification. The advantageous vesicle structure enhanced photoabsorption via the light scattering effect, while further carbon modification provided an efficient pathway to promote charge speration and transfer, which demonstrated that the carbon derived from the organic template residues (hexadecyl trimethyl ammonium bromide) was a facile yet effective medium to optimize the photocatalysis of C3N4.