Abstract:
The reduced graphene oxide (RGO)-based
composites have attracted intensive attention in research due
to its superior performance as photocatalysts, but still lacking is
the theoretical understanding on the interactions between
constituents, as well as the connection between such interaction
and the enhanced photoactivity. Herein, the interaction between
the g-C3N4 and RGO sheets is systematically explored by using
state-of-the-art hybrid density functional theory. We demonstrate that the O atom plays a crucial role in the RGO-based
composites. Compared to the isolated g-C3N4 monolayer, the
band gap of composites obviously decreases, and at higher O
concentration, the levels in the vicinity of Fermi level are much more dispersive, indicating the smaller effective mass of the
carrier. These changes are nonlinear on the O concentration. Interestingly, appropriate O concentration alters the direct-gap
composite to indirect-gap one. Most importantly, at a higher O concentration, a type-II, staggered band alignment can be
obtained in the g-C3N4-RGO interface, and negatively charged O atoms in the RGO are active sites, leading to the high
hydrogen-evolution activity. Furthermore, the calculated absorption spectra which vary with the O concentration shed light on
different experimental results. The findings pave the way for developing RGO-based composites for photocatalytic applications.
