CdS quantum dots (QDs) were decorated onto phosphorus-doped hexagonal g-C3N4 tube (P-CNT) to form a novel high-preformance photocatalyst (CdS QDs/P-CNT) via an in-situ oil bath approach. The ultra-small CdS QDs with the average diameter of similar to 9 nm are homogeneously anchored on the both external and internal surface of P-CNT hollow channel (similar to 25 mu m), yielding a type of zero-dimensional (0D)/one-dimensional (1D) heterojunction. The CdS QDs/P-CNT-1 exhibits the maximum photocatalytic H-2 evolution rate of 1579 mu mol h(-1) g(-1) under visible-light irradiation, which is 31.6, 6.8, 4.7 and 3.1 times higher than P-CNT, CdS, CdS/BCN and CdS/CNT, respectively. The improved photocatalytic activity of CdS QDs/P-CNT is primarily attributed to large surface area, P doping and formed 0D/1D heterojunction, which can broaden the light absorption, narrow the band gap, activate the H2O molecule and promote the spatial charge separation. Moreover, the DFT calculation coupled with experiment (Mott-Schottky curves) illustrates the electron transfer behavior of CdS QDs/P-CNT, showing that the Cd-1 site should be the main active center and P doping is beneficial to increase H-2 production. This work provides a new strategy to design of highly active 0D/1D photocatalyst for photocatalytic H-2 production. (C) 2020 Elsevier Inc. All rights reserved.