Enhancing Urea Electrosynthesis From CO2 and Nitrate Through High-Entropy Alloying

Abstract

Ordered intermetallic compounds, one of the most effective alloying ways of enhancing electrocatalytic activity may provide more active sites for intermediates adsorption in single catalytic reactions. However, for catalysis involving several starting materials (such as the co-catalytic synthesis of urea from CO₂ and NO₃⁻), it typically cannot favor multiple intermediates adsorption, leading to preferred individual catalysis and preventing effective C─N coupling. As a proof of concept, AuCuIrCo medium-entropy intermetallic (MEI) compounds are synthesized and use Pd to disrupt the ordered arrangement, achieving PdAuCuIrCo high-entropy alloy (HEA) counterpart for co-catalytic urea synthesis. In situ spectroscopic analyses indicate that the MEI produces greater NH₃–resultant of sole NO₃⁻ reduction, while HEA yields more C─N coupling products. Theoretical calculations indicate that the HEA shows a reduced ^*NO₂ adsorption energy compared to MEI and lowers energy barriers for both C─N coupling and hydrogenation processes, allowing for effective co-adsorption with ^*CO₂, whereas the MEI excessively stabilizes ^*NO₂, favoring a single-pathway reduction to NH₃. Consequently, the HEA achieves a high urea yield rate of 52.43 mmol h⁻¹ g⁻¹ and a Faradaic efficiency of 22.57% at −0.9 V, greatly surpassing the MEI. This study provides a framework for the development of multi-pathway electrocatalytic reactions.