Abstract: Molybdenum selenide (MoSe₂) has been regarded as an advanced electrocatalyst for the hydrogen evolution reaction (HER). However, its electrocatalytic performance is far inferior to platinum (Pt). Combining semiconductors with metals to construct Mott-Schottky heterojunctions has been considered as an effective method to enhance HER activity. In this work, we report a typical Mott-Schottky heterojunction composed of metal Co and semiconductor MoSe₂ on carbon nanotubes (Co/MoSe₂@CNT), prepared by a sol-gel process followed by thermal reduction. The characterization and theoretical calculations show that a Co/MoSe₂ Mott-Schottky heterojunction can cause electron redistribution at the interface and form a built-in electric field, which not only optimizes the free energy of hydrogen atom adsorption, but also improves the charge transfer efficiency during hydrogen evolution. Thus, the Co/MoSe₂@CNT has excellent catalytic activity with a low overpotential of 185 mV at 10 mA cm⁻² and a small Tafel slope of 69 mV dec⁻¹. This work provides a new strategy for constructing Co/MoSe₂ Mott-Schottky heterojunctions and highlights the Mott-Schottky effect, which may inspire the future development of more attractive Mott-Schottky electrocatalysts for H₂ production.