New Mechanism for N₂ Reduction: The Essential Role of Surface Hydrogenation

Electrocatalytic N₂ reduction is one of the most promising ways for green and sustainable production of NH₃. However, a mechanistic understanding of the N₂ reduction process remains very limited. Herein, a surface-hydrogenation mechanism for the N₂ reduction reaction is proposed, which can well address the recently emerged sharp discrepancies between experiments and computations. Our results reveal that surface hydrogenation can drive N₂ reduction reaction on catalysts with weak N₂-binding strength (i.e., noble-metal catalysts) at low potentials. Instead of N₂ adsorption, the reduction of H⁺ is found to be the first step, which is also the potential determining step of the whole process. N₂ can be activated and reduced into *N₂H₂ subsequently by overcoming relatively high energy barriers, which determines the total reaction rate. Moreover, the cooperative effect of surface *H and the catalysts plays a key role in the activation of N₂. Our work not only provides new insights into the N₂ reduction reaction, but also paves a promising way for advancing sustainable NH₃ production.