Dual-site cooperation for synergistic optimization of the band structure and spin state to facilitate C–N coupling reaction
Qizhu Qian, Qilong Liu, Mengxiang Wang, Jingjing Yang, Huiyi Li, Wei Bai, Wentao Wang, Changzheng Wu, Chong Xiao, Yi Xie
Abstract
The emerging electrocatalytic C–N coupling reaction provides an attractive route toward green urea synthesis, but a lack of in-depth insight into the catalytic mechanism and the geometric/electronic configurations that determine the key C- and N-coupling intermediates formation hampers the exploration of efficient catalysts. Herein, we design a bimetallic oxide (Fe-Mo-O) with dual active sites of Fe and Mo for the adsorption and activation of NO 2 − and CO 2 , respectively. Constructing dual-metal catalyst leads to an upshift of the d-band center and the generation of an intermediate-spin Fe center, which not only favors the selective conversion of *CO 2 into the key intermediate *CO on Mo sites, but also facilitates the adsorption and reduction of NO 2 − on Fe sites. Operando characterizations and theoretical calculations together elucidate that urea generation is associated with the formation of *CONH 2 intermediate by coupling *CO and *NH 2 on the alternating Mo and intermediate-spin Fe active sites, ultimately synergistically lowering the C–N coupling energy barrier. Specifically, the Fe-Mo-O catalyst delivers a high urea yield rate of 681.8 μg h −1 mg −1 cat. and an excellent Faradaic efficiency of 60% at −0.5 V (vs. RHE). Furthermore, a C–N coupling paired with a glycerol oxidation system allows for energy-saving electrochemical coproduction of urea and formic acid. Our findings offer a feasible strategy to develop cutting-edge electrocatalysts for urea synthesis by active site design and electronic structure regulation.