Plasma catalytic synthesis of ammonia has the advantages of flexible on-off and environmental friendliness, making ammonia a potential vector for renewable energy storage. The synergistic interaction between plasmas and catalyst surfaces remains unclear. In this work, we develop a quantum chemical model based on density functional theory where the plasma environment is simplified. The effect of electric fields and surface electrons on N2 adsorption and dissociation is studied on the typical catalysts (Ru and Ni) with different surface morphologies. The combined effect of the electric fields and excess electrons will promote the adsorption of N2 and the weakening of the NN triple bond. It is shown that the electron distribution on the surface is optimized, and the electrostatic interaction between surface atoms and adsorbates is strengthened. The marginal effect has been observed, and the promotion effect on the catalysts with better performance in thermal-catalytic N2 dissociation is weaker.