Beyond Initial Adsorption: Solvated First‐Hydrogenation Kinetics Govern Potential‐Dependent NRR – HER Selectivity on Dual‐Atom Catalysts

Electrochemical nitrogen reduction reaction (NRR) offers a promising route for ammonia synthesis under ambient conditions, but its efficiency is severely limited by the competing hydrogen evolution reaction. Computational screening commonly assesses NRR–HER selectivity from the initial adsorption preference between *N 2 and *H. However, this static descriptor does not establish whether an N 2 ‐covered catalyst will subsequently favor N 2 hydrogenation over neighboring‐site H adsorption. Here, using homonuclear transition‐metal dimers anchored on C 2 N as model dual‐atom catalysts, we examine this competition through a hybrid explicit/implicit solvation model and pathway‐resolved kinetic analysis. Solvation alters the stability of key *NNH intermediates and narrows the set of kinetically viable candidates. The remaining catalysts exhibit distinct competition between direct *N 2 hydrogenation and Volmer‐type H adsorption, with applied potential further modifying the accessibility of both pathways. These results demonstrate that favorable initial *N 2 adsorption alone is insufficient to predict sustained NRR selectivity. Instead, solvated first‐hydrogenation kinetics and potential‐dependent pathway branching provide a more rigorous mechanistic framework for evaluating NRR–HER competition on dual‐site catalysts.