We have found that an electric field brings high yield on low temperature catalytic ammonia synthesis over Cs/Ru/SrZrO3 catalyst. The role of the electric field is investigated based on kinetics and isotope effects. Results show that the electric field promotes proton hopping on the catalyst surface, and it brings a change in the reaction mechanism from the conventional one to the N2H+ intermediate mechanism. In the electric field, N2H+ intermediate plays an important role, enabling low-temperature ammonia synthesis.