Theoretical insights on C-N coupling mechanism and guidance for screening the catalysts of electrocatalytic urea synthesis by descriptors

Abstract

Electrocatalytic urea synthesis from CO2 and nitrate/nitrite is promising as a sustainable strategy to alleviate the dependency on fossil resources and CO2 release. The complicated synthesis steps and controversial C-N coupling mechanism restrict the design of efficient catalysts to satisfy industrial application. Herein, based on density functional theory calculations on metals (Au, Ag, Pd, Cu, and Ni) and micro-kinetic analysis, the C-N coupling mechanism is clarified as CO2+ N1 species (NO*, NOH*, or N*). The formed chemical adsorption of CO2 on the surface is found as an indicator to directly exclude the inactive metal catalysts. Furthermore, the descriptors of hydrogen and oxygen adsorption energy are successfully related to the catalysis performance, and the catalysts with moderate hydrogen adsorption and strong oxygen adsorption strength are predicted with the outstanding performance, which is validated by the experimental results. These insights would be helpful to identify and design high-performance catalysts for electrocatalytic urea synthesis.