Novel carbon dots (CDs)/graphitic carbon nitride (g-C3N4) hybrids were fabricated via an in situ thermal polymerization of the precursors, urea and glucose. This heterojunction catalyst exhibited enhanced photocatalytic H-2 evolution activity under visible-light ( lambda > 420). A sample of CDs/g-C3N4 hybrids, CN/G0.5, which was prepared from 0.5 mg of glucose in 6.0 g of urea (8.3 x 10(-3) wt% glucose), exhibited the best photocatalytic performance for hydrogen production from water under visible light irradiation, which is about 4.55 times of that of the bulk g-C3N4 (BCN). The improvement of photocatalytic activity was mainly attributed to the construction of built-in electric field at the interface of CDs and g-C3N4, which could improve the separation of photogenerated electron-hole pair. Moreover, the tight connection of CDs with g-C3N4 would serve as a well electron transport channel, which could promote the photocatalytic H-2 evolution ability. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.