We successfully prepared nitrogen-doped defective carbon spheres (Mo-N4/d-C) with a high loading of 0.996 wt % via a designed vapor-deposition process for IOR-based hydrogen generation. The synthesized Mo-N4/d-C catalyst provides a record current density of 10 mA cm–2 at 0.77 V. Further, the Mo-N4/d-C catalyst shows a Tafel slope of 25.58 mV dec–1, exceptional stability over time in acidic media, a higher hydrogen generation rate of 0.1063 mL gcat –1 min–1, a high Faradaic efficiency of 99.8%, and a reduction of the energy consumption up to ∼50% for hydrogen evolution by anodic oxidation reaction of iodide (IOR) compared with the conventional OER-based electrolysis. Computational calculations demonstrate that the Mo-N4/d-C structure plays a vital effect on the activity of iodide oxidation, which is competitive with the Pt catalyst.