Among hydrogen storage chemicals for proton exchange membrane fuel cells (PEMFCs), sodium borohydride stands out for yielding exceptionally pure hydrogen. This study synthesized cobalt-molybdenum catalysts supported on g-C3N4 using an ultrasonic-assisted impregnation method. Various CoMo/g-C3N4 catalysts with different CoMo mass ratios were created, all showing high hydrogen production and complete NaBH4 conversion under mild conditions. Catalytic activity depends on the cobalt-molybdenum mass ratio, with optimal performance at a 1:1 ratio (w/w), maintaining up to 83% activity over 5 cycles. The effect of operating conditions on hydrogen release was explored, resulting in the rate law: rH2 = 1.708 × 10-3 [NaBH4]1.25 [Catalyst dosage]1.39 [NaOH]0.44 at 298 K, with a low activation energy of 22.9 kJ mol−1. Molybdenum's promoting effect prevented significant deactivation of the cobalt catalyst, ensuring complete NaBH4 conversion to H2 and good stability over multiple cycles.