C─N Coupling Enabled by N─N Bond Breaking for Electrochemical Urea Production

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Abstract
Urea electrosynthesis under mild conditions has emerged as a promising alternative strategy to replace the harsh industrial HaberBosch process, which is however limited by sluggish CN coupling and low selectivity. Here, a novel mechanism based on the synergistic effect of NN bond cleavage and CN coupling for highly efficient urea production is proposed. It is found that dual vanadium atoms anchoring onto defective graphene (V2N6) can activate the adsorbed *N2, in which the stable N≡N bond can be gradually weakened until being broken after two protonation steps, with superior thermodynamic and kinetic feasibility. CO molecules can be easily adsorbed on the dissociated *NH, followed by an exothermic CN coupling to form the urea precursor *NHCONH with a low kinetic energy barrier of 0.20 eV. The dual‐atom V2N6 not only exhibits superior intrinsic activity for urea formation, with a limiting potential of −0.26 V, but also can significantly suppress the competitive N2 reduction and hydrogen evolution reactions. This study presents a new avenue for developing novel mechanisms and efficient catalysts for urea electrochemical synthesis.

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