Photocatalytic water splitting for hydrogen evolution is one of the most promising methods to mitigate environmental and energyrelated issues. In this study, manganese cadmium sulfide (Mn x Cd 1x S) solid solution is used to construct a p-n heterostructure with NiCo 2 O 4 through a hydrothermal method. The Mn 0.25 Cd 0.75 S/ NiCo 2 O 4 composites are used for photocatalytic hydrogen evolution reaction, and the optimal hydrogen rate with 40 mg of Mn 0.25 Cd 0.75 S/NiCo 2 O 4 40 mg (MCS/NCO 40) is 61159 μmol g À 1 h À 1 , which is about 16.3 times than that of pure Mn 0.25 Cd 0.75 S. After combining with NiCo 2 O 4 , the light absorption scale, the separation efficiency of photogenerated carriers, and the reaction kinetics are enhanced. Moreover, the band offset of MCS/NCO composites is calculated by the core level alignment method, demonstrating the formation of a p-n heterostructure. The built-in electric field from the p-n heterostructure drives charge transfer and enhances separation efficiency, which results in improved photocatalytic performance.