Controllable C─N Coupling Toward Efficient Urea Electrosynthesis via Spin State Modulation on Fe Catalysts

Abstract The co‐electrolysis of CO 2 and nitrate (NO 3 − ) presents a promising and sustainable method for urea synthesis. However, it remains challenging to modulate the intermediates reactivity and C─N coupling at the matchable stages. Here, we propose a strategy to regulate the C─N coupling mode on Fe site via spin state modulation. Both experimental and theoretical calculations revealed that the Cu 2+ ‐doped Fe 3 O 4 promoted C─N coupling at the early stage via the *CO + *NO 2 →*CONO 2 pathway, enhancing the catalytic performance significantly. The catalysts could achieve a urea Faradaic efficiency of 47.3% and a yield rate of 635.9 µg h −1 mg cat. −1 at low overpotential, along with exceptional stability over 30 h, representing one of the highest performances reported to date. Detailed experimental and theoretical analyses demonstrated that Cu doping lowered the e g electron density of Fe and enhanced *NO 2 adsorption. The adsorbed *NO 2 in turn further decreased Fe spin state through π backdonation, which facilitated CO 2 activation and increased *CO coverage. Moreover, optimizing the *NO 2 coverage also reduced the energy barrier for *CO + *NO 2 →*CONO 2 , and inhibited *NO 2 protonation, leading to high selectivity toward urea.