Quaternary Medium-Entropy Alloy Metallene with Strong Charge Polarization for Highly Selective Urea Electrosynthesis from Carbon Dioxide and Nitrate
Yuanbo Zhou, Mengfan Wang, Lifang Zhang, Najun Li, Tao Qian, Chenglin Yan, Jianmei Lu
Abstract
Electrochemical urea synthesis via the coreduction of CO 2 and NO 3 – is a sustainable alternative to the traditional Bosch–Meiser process. However, the sluggish reaction kinetics usually result in a low efficiency. Herein, we designed a kind of quaternary PdCuCoZn medium-entropy alloy (MEA) metallene for highly selective urea electrosynthesis. The random occupation of Cu, Co, and Zn with lower electronegativity in the face-centered cubic lattice of Pd-based metallene enables abundant electron donation from transition metals to adjacent Pd atoms, leading to the formation of charge-polarized Pd δ− –Cu/Co/Zn δ+ sites. Considering that the pivotal C- and N-intermediates, namely, *CO and *NH 2, are electrophilic and nucleophilic, respectively, such strong charge polarization would greatly benefit their respective formation and stabilization. The stable adsorption with *CO bonded to electron-rich Pd-based sites and *NH 2 bonded to electron-deficient Cu/Co/Zn-based sites is demonstrated by the combination of in situ characterizations and theoretical calculations. The proof-of-concept PdCuCoZn MEA metallene achieves a maximum urea yield rate of 1840 μg h –1 mg –1 and a high Faradaic efficiency of 70.2%, surpassing most of the reported state-of-the-arts. Our strategy proposed in this work is believed to enlighten the design of an effective catalyst used for multistep reactions.