Cu-Ni alloy nanocrystals with heterogenous active sites for efficient urea synthesis

Abstract

Electrocatalytic urea synthesis from CO2 and NO3− are environmental green and energy savable. Although Cu are effective for CO2 and NO3− reduction reactions, achieving high efficiency of urea production remains challenging. Herein, Cu-Ni nanocrystals are formed to provide heterogenous active sites for promoting hydrogenation and C−N coupling reactions in urea synthesis. The carbon supported Cu-Ni nanocrystals are characterized by extended X-ray absorption fine structure and X-ray photoelectron spectroscopy spectra. The Cu-Ni nanocrystals achieves the highest urea Faradaic efficiency of 25.1 % and urea yield of 22.01 μmol h−1 cm−1, which is much higher than that of single Cu or Ni metal. The reaction mechanism is probed by in-situ Fourier transform infrared spectroscopy, revealing a C−N coupling reaction pathway between *CO and *NH2. Theoretical calculations suggest that hydrogenation of *NOx and coupling *CO with *NH2 are more easily occurred over co-existed Cu and Ni sites rather than homogeneous Cu or Ni site.