Hexagonal molybdenum carbide (Mo₂C) as an effective non-noble cocatalyst is intensively researched in the photocatalytic H₂-evolution field owing to its Pt-like H⁺-adsorption ability and good conductivity. However, hexagonal Mo₂C-modified photocatalysts possess a limited H₂-evolution rate because of the weak H-desorption ability. To further improve the activity, cubic MoC was introduced into Mo₂C to form the carbon-modified MoC-Mo₂C nanoparticles (MoC-Mo₂C@C) by a calcination method. The resultant MoC-Mo₂C@C (ca. 5 nm) was eventually coupled with TiO₂ to acquire high-efficiency TiO₂/MoC-Mo₂C@C by electrostatic self-assembly. The highest H₂-generation rate of TiO₂/MoC-Mo₂C@C reached of 918 μmol·h⁻¹·g⁻¹, which was 91.8, 2.7, and 1.5 times than that of the TiO₂, TiO₂/MoC@C, and TiO₂/Mo₂C@C, respectively. The enhanced rate of TiO₂ attributes to the carbon layer as cocatalyst to transmit electrons and the hetero-phase MoC-Mo₂C as H₂-generation active sites to boost H₂-evolution reaction. This research offers a novel insight to design photocatalytic materials for energy applications.