C─N Coupling Enabled by N─N Bond Breaking for Electrochemical Urea Production
Junxian Liu, Sean C. Smith, Yuantong Gu, Liangzhi Kou
Abstract
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 CN coupling and low selectivity. Here, a novel mechanism based on the synergistic effect of NN bond cleavage and CN coupling for highly efficient urea production is proposed. It is found that dual vanadium atoms anchoring onto defective graphene (V 2 N 6 ) can activate the adsorbed *N 2 , 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 CN coupling to form the urea precursor *NHCONH with a low kinetic energy barrier of 0.20 eV. The dual‐atom V 2 N 6 not only exhibits superior intrinsic activity for urea formation, with a limiting potential of −0.26 V, but also can significantly suppress the competitive N 2 reduction and hydrogen evolution reactions. This study presents a new avenue for developing novel mechanisms and efficient catalysts for urea electrochemical synthesis.