Electrocatalytic reduction of nitrate (NO₃⁻ , NO₃RR) provides an effective strategy to mitigate water pollution of human-caused but obtain high-value ammonia (NH₃) under environmental conditions based on renewable energy. In this study, we prepared porous carbon nanofibers (CFs)-supported CuCo₂O₄ composite (CuCo₂O₄/CFs) electrocatalyst by electrospun-pyrolysis method for efficient conversion of NO₃⁻ to NH₃. The experimental results revealed that the CFs could contribute to charge transfer and inhibit the hydrogen evolution reaction (HER), which preferentially catalyzes NO₃⁻ -to- NO₂⁻. On the other hand, internally confined CuCo₂O₄ nanoparticles conduce to stabilize adsorbed nitrite intermediate (*NO₂) for further conversion to NH₃. The CuCo₂O₄/CFs exhibit the maximum NH₃ Faradaic efficiency of 81.9 % at − 0.3 V versus reversible hydrogen electrode (vs RHE) with a yield rate of 394.5 mmol h⁻¹ g⁻¹ at ambient conditions. The theoretical analysis demonstrated that the *NH₃ desorption is a potential rate-determining step (RDS) with an uphill energy change of 0.76 eV over CuCo₂O₄. Furthermore, CuCo₂O₄/CFs as difunctional catalysts, coupling NO₃⁻ reduction with methanol oxidation (NO₃RR||MOR) to substitute water splitting simultaneously at a low voltage. This work provides a strategy for combining NH3 electrosynthesis with methanol oxidation to high value-added chemicals under ambient conditions.