An efficient ternary Mn0.2Cd0.8S/MoS2/Co3O4 heterojunction was prepared and displayed excellent photocatalytic performance. The ternary Mn0.2Cd0.8S/MoS2/Co3O4 heterojunction with 0.62 wt% of MoS2 and 1.51 wt% of Co3O4 achieved the highest H-2 evolution activity (16.45 mmol g(-1) h(-1)), which was well above Mn0.2Cd0.8S (2.72 mmol g(-1) h(-1)). The improved H-2 evolution activity was ascribed to the synergistic effect of the Mn0.2Cd0.8S/Co3O4 p-n heterojunction and the modification of MoS2 as a co-catalyst. This work can offer a new perspective for the application of MnxCd1-xS-based ternary heterojunction towards solar energy conversion. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.