The electrocatalytic nitrogen reduction reaction (NRR) under mild conditions is one of the most essential challenges in chemistry. Catalysts for electrochemical NRR play a crucial role in realizing this NH3 synthesis. In this work, we use density functional theory simulations to investigate the electro-catalytic NRR selectivity and activity on dual-atom catalysts, especially diporphyrins. We classify catalysts on the basis of adsorption of *N2 versus *H. Our results demonstrate the possibility of diporphyrins to bind and reduce N2 without producing H2 under ambient conditions, promoting high selectivity toward NH3 formation. This is due to chelating adsorption of N2, where N2 sits between two metal atoms, enhancing the binding of *N2. Additionally, the chelating adsorption of N2 activates N-N bond breaking and provides more favorable scaling relations on the adsorption energies of key intermediates, leading to enhanced NRR activity.