Hard Lewis Acid Mo6+ Orchestrates N-End Urea Adsorption to Steer Highly Selective Nitrite Electrosynthesis.

Electrocatalytic urea oxidation reaction (UOR) offers a promising route for coupling wastewater remediation with nitrogen upgrading. However, the structural complexity of urea, containing both electron-donating (─NH2) and electron-withdrawing (C = O) groups, leads to multiple adsorption configurations, resulting in poorly defined pathways and low selectivity toward nitrite (NO2 ‾). Here, guided by Pearson's hard-soft acid-base theory, we develop a hard Lewis acid strategy by incorporating Mo6+ into NiCo layered double hydroxide (NiCoMo-LDH) to regulate interfacial electronic structure. The strong electron-accepting nature of Mo6+ regulates the electronic environment of Ni/Co centers, facilitating the formation and stabilization of high-valent NiOOH/CoOOH species while creating polarized interfacial sites with enhanced affinity toward urea activation. Importantly, Mo-induced modulation does not merely increase oxidative capability; instead, it introduces substrate-specific adsorption regulation that favors UOR over the competing OER. This configuration regulation facilitates selective C-N bond cleavage of the *NCONH2 intermediate and subsequent oxidation of the generated nitrogen species toward NO2 ‾, achieving a Faradaic efficiency of 93.4% and a production rate of 1732.7 µmol h-1 cm-2. This work establishes Lewis acid modulation as a strategy for controlling adsorption configurations and steering selective electrosynthesis.