Enabling Unconventional "Alternating-Distal" N2 Reduction Pathway for Efficient Ammonia Electrosynthesis.

Electrocatalytic dinitrogen reduction reaction under ambient conditions offers a promising approach for sustainable and decentralized green ammonia production. Conventionally, the general understanding on the reaction path is that the N2 reduction follows either individual associative alternating or distal pathways, where efficient N2 activation and selective NH3 production are very challenging. Herein, an unconventional "alternating-distal" hybrid pathway was achieved by shifting the "*NHNH2→*NH2NH2" to "*NHNH2→*NH + NH3" step to boost NH3 synthesis with an amorphous CeMnOx electrocatalyst. In this unconventional process, N2 activation was realized through π back donation on the Mn site, while the Mn/Ce dual active sites could regulate the intermediate configurations to avoid the nitrogen-containing by-product formation for guaranteeing high NH3-producing Faradaic efficiency. Such "alternating-distal" hybrid pathway was validated by a set of in situ spectroscopic analyses and theoretical calculations. In a neutral media, an average ammonia production rate of 82.8 μg h-1 mg-1 and an outstanding Faradaic efficiency of 37.3 % were attained on the amorphous CeMnOx electrocatalyst at a mild potential of -0.2 V, along with an impressive durability of over 40 hours. This work validated an unconventional mechanism in electrocatalytic ammonia synthesis, which might be extended to other catalytic process with multiple possible reaction paths.