This study investigates the spin-related Cu-Co synergistic effect on electrochemical nitrate-to-ammonia conversion using high-entropy oxide Mg0.2Co0.2Ni0.2Cu0.2Zn0.2O. The results show that the Cu-Co pair with a high spin Co in Mg0.2Co0.2Ni0.2Cu0.2Zn0.2O facilitates ammonia generation, while a low spin Co in Li-incorporated MgCoNiCuZnO decreases the synergistic effect. The electronic structure analysis reveals that the Co spin states are crucial for the Cu-Co synergistic effect. The findings offer insights into the role of spin states in selective catalysis and highlight the generality of the magnetic effect in ammonia synthesis between electrocatalysis and thermal catalysis. The high-entropy oxide Mg0.2Co0.2Ni0.2Cu0.2Zn0.2O exhibits excellent catalytic performance, with a Faradaic efficiency of 99.3% and a yield rate of 26.6 mg cat−1 h−1, making it a promising material for ammonia generation.This study investigates the spin-related Cu-Co synergistic effect on electrochemical nitrate-to-ammonia conversion using high-entropy oxide Mg0.2Co0.2Ni0.2Cu0.2Zn0.2O. The results show that the Cu-Co pair with a high spin Co in Mg0.2Co0.2Ni0.2Cu0.2Zn0.2O facilitates ammonia generation, while a low spin Co in Li-incorporated MgCoNiCuZnO decreases the synergistic effect. The electronic structure analysis reveals that the Co spin states are crucial for the Cu-Co synergistic effect. The findings offer insights into the role of spin states in selective catalysis and highlight the generality of the magnetic effect in ammonia synthesis between electrocatalysis and thermal catalysis. The high-entropy oxide Mg0.2Co0.2Ni0.2Cu0.2Zn0.2O exhibits excellent catalytic performance, with a Faradaic efficiency of 99.3% and a yield rate of 26.6 mg cat−1 h−1, making it a promising material for ammonia generation.