The design and development of noble metal-free, low-cost and stable co-catalyst are of great significance to the practical application of photocatalysts. In this work, the Mo incorporated Ni nanosheets (MoNi NSs) are successfully prepared and loaded onto g-C3N4 via a simple and controllable method. The controlled loading of MoNi NSs with an optimal Mo intake can greatly enhance the photocatalytic H-2-evolution property of g-C3N4 (Mo0.25Ni0.75/CN5). Specifically, the Mo0.25Ni0.25/CN5 exhibits the highest photocatalytic H-2-evolution rate of 273.2 mu mol (5464 mu mol which is the highest rate under one-solar light in the g-C3N4 systems coupled with noble-metal-free co-catalysts. The greatly enhanced photocatalytic H-2-evolution activity of MoNi/g-C3N4 is attributed to the role of MoNi as an outstanding co-catalyst to promote the carriers' separation and transfer, and accelerate the surface H-2 evolution reaction (HER). (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved. The design and development of noble metal-free, low-cost and stable co-catalyst are of great significance to the practical application of photocatalysts. In this work, the Mo incorporated Ni nanosheets (MoNi NSs) are successfully prepared and loaded onto g-C3N4 via a simple and controllable method. The controlled loading of MoNi NSs with an optimal Mo intake can greatly enhance the photocatalytic H-2-evolution property of g-C3N4 (Mo0.25Ni0.75/CN5). Specifically, the Mo0.25Ni0.25/CN5 exhibits the highest photocatalytic H-2-evolution rate of 273.2 mu mol (5464 mu mol which is the highest rate under one- solar light in the g-C3N4 systems coupled with noble-metal-free co-catalysts. The greatly enhanced photocatalytic H-2-evolution activity of MoNi/g-C3N4 is attributed to the role of MoNi as an outstanding co-catalyst to promote the carriers' separation and transfer, and accelerate the surface H-2 evolution reaction (HER). (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.