Controllable C─N Coupling Toward Efficient Urea Electrosynthesis via Spin State Modulation on Fe Catalysts
Limin Wu, Shunhan Jia, Yongbin Li, Chongzhi Zheng, Ruhan Wang, Libing Zhang, Xiangyuan Jin, Rongjuan Feng, Liang Xu, Xinchen Kang, Qinggong Zhu, Qingli Qian, Ying Xu, Xiaofu Sun, Buxing Han
Abstract
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.