The challenge in electrocatalysis lies in finding stable and efficient catalysts for hydrogen evolution, especially those based on non-noble metals. Herein, the Mo5O14-Y(OH)3-CoMoO4/CF (CF stands for cobalt foam) catalyst rich in ternary heterostructures have been successfully synthesized. The catalyst is composed of cumin-like nanoparticles randomly dispersed on microcolumns. This unique structure ensures both its electrocatalytic activity and structural stability. Electrochemical tests demonstrate exceptional water splitting capabilities, with overpotentials of just 40 mV at 10 mA cm−2 (j10) and 219 mV at 1000 mA cm−2 (j1000). Furthermore, the catalyst shows minimal performance degradation after long-term testing, maintaining stable electrochemical performance for 60 h at j10 and 18 h at j800. Surface energy calculations and scanning electron microscopy (SEM) indicate that yttrium(Y) promotes the formation of cumin-like nanoparticles. Density functional theory (DFT) analysis, along with in situ Raman spectroscopy, suggests that the interaction among the three metals forms Mo5O14-Y(OH)3-CoMoO4 ternary heterostructures, effectively reducing the energy barrier for the hydrogen evolution reaction (HER). Notably, the Y sites in the CoMoO4-Y(OH)3 heterostructure exhibit the lowest hydrogen adsorption free energy (ΔGH⁎: −0.31 eV), making them the primary active sites for Mo5O14-Y(OH)3-CoMoO4/CF.