Developing low-cost high-efficient electrocatalysts for alkaline hydrogen evolution reaction (HER) is of critical significance in hydrogen production via alkaline electrolyzers. Herein, we prepared CeO₂/Co₄N heterostructure for the catalyst in alkaline HER, which introduced a synergistic effect within the CeO₂ and Co₄N catalytic sites that facilitates the two consecutive steps in alkaline HER reaction. More importantly, plasma treatment was further applied to the material to tune the electronic structure of the catalytic sites by creating multiple anion vacancies. The introduced O vacancies accelerated the H₂O cleaving process on CeO₂, while the N vacancies in Co₄N optimized the H adsorption strength on the Co sites. The catalytic activity of the catalyst improved significantly after plasma treatment. It only required an overpotential of 36 mV@10 mA cm⁻² for the HER operated in 1 M KOH electrolyte and provided one of the best precious metal-free catalysts ever reported.