In Situ Tailored Frustrated Lewis Pairs on Asymmetric Bi─O_v─In Motifs Domino-Direct High-Efficiency Urea Electrosynthesis.

Abstract

The green urea synthesis via co-electrolysis of waste nitrate and CO₂ is alluring but challenging, especially with insufficient selectivity caused by thermodynamic differences and kinetic mismatch between multi-step conversion processes. Here, a domino effect-oriented electrosynthesis strategy is showcased to steer cascade reactions in upgrading nitrate and CO₂ toward urea of high selectivity on Bi-doped In₂O₃ with asymmetric oxygen vacancies (O_v). The conventionally arbitrary reaction mode can be vectored and re-customized by stable and cumulative ^*NH₂ intermediates in situ derived from priority nitrate reduction reaction, which not only form surface frustrated Lewis pairs (SFLPs, Bi─O_v─In─NH₂) with Bi Lewis acid sites to synergistically adsorb and activate CO₂ but also provide more opportunities for sluggish C─N coupling, delivering an unprecedented urea Faradic efficiency of 80.2% and an impressive urea yield of 2.38 × 10³ µg h^-1 mg_cat. ^-1 at -0.4 V versus RHE. The atomically dispersed Bi sites promote the protonation of ^*NO to form nucleophilic ^*NH₂ intermediates, which can be stabilized in the electrophilic region mediated by asymmetric O_v, permitting two nucleophilic attacks to complete the C─N coupling. The domino modeling protocol via positioning a specific intermediate in situ tailors the parallel conversion process and may guide selectivity control of electrosynthesis.