Strengthened d-π Interaction in Bimetallic Cluster for Boosted Urea Electrosynthesis from Nitrate and CO2 in Simulated Industrial Waste

Abstract

Electrocatalytic conversion of NO3- and CO2 offers a viable strategy for waste resource utilization. However, current studies largely focuses on high-concentration systems, while efficient electrocatalytic synthesis under realistic low-concentration polluted conditions remains in its infancy. Herein, we report a bimetallic cluster CuI4FeII (CuI4FeII(PPh3)4L6, L = tetrazole) via strategic FeII-for-CuII substitution. The experiment shows that under the conditions of -0.64 V vs. RHE, 100% CO2 and 50 mM NO3-, the Faradaic efficiency (FE) of urea using this catalyst reaches 62%, which is twice that of CuI4CuII and is the best among the clusters. Under simulated real-world low-concentration conditions (20% CO2, 600 ppm NO3-), the CuI4FeII maintains a FE of 41% and exhibits robust catalytic performance across a wide range of CO2 and NO3- concentrations. Mechanistic studies reveal that the introduction of the Fe site induces significant electronic restructuring, which not only enhances NO3- adsorption and reduces its protonation energy barrier but also strengthens the d-π interactions between metal orbitals and key intermediates. This effect effectively lowers the overall reaction energy barriers and facilitates CO2 insertion and subsequent C–N coupling, thereby rationalizing the observed high catalytic activity. This work demonstrates heterometallic synergy for efficient multi-step electrocatalysis under practical conditions.