Interfacial manipulation of nanostructured heterojunction photocatalysts to enhance charge separation and transfer is highly desirable to achieve a high photocatalytic activity. In this work, a well-designed non-noblemetal Mo2C@C/g-C3N4 heterostructure is constructed, in which the intercalated carbon nanosheets serve as a binder to form an excellent interfacial contact between Mo2C and g-C3N4. In addition, large quantities of carbon quantum dotsare found to be homogeneously embedded in the carbon nanosheets. The as-obtained Mo2C@C/gC(3)N(4) hybrid exhibits a remarkably improved photocatalytic H-2 evolution rate of 52.1 mu mol h(-1) under visible-light irradiation (lambda >= 420 nm) without co-catalyst, which is up to nearly 260 times higher than that of pristine gC(3)N(4)(0.2 mu mol h(-1)) under the same conditions. The significant increase in photocatalytic activity mainly results from the fast charge migration and separation between Mo2C and g-C3N4 facilitated by the conducing carbon nanosheets as an efficient electron mediator. Moreover, the carbon quantum dots embedded in the carbon support also promotes solar energy utilization. This work highlights a feasible strategy to explore highly efficient photocatalysts via interfacial engineering on heterojunction composites.