Electroreduction of N2 and CO2 to urea via Pd-assisted hydrogenation on MOF-derived CeO2 nanosheets

Abstract

Conversion of CO₂ and N₂ to urea by electrocatalytic methods under ambient conditions is a promising alternative to conventional methods of urea synthesis. However, the inherent adsorption and activation characteristics of the inert reaction gas molecules and the kinetics of hydrogenation after C–N coupling make the electrocatalytic synthesis of urea challenging. In this work, the electrocatalytic conversion of CO₂ and N₂ to urea by Pd-assisted hydrogenation was achieved on CeO₂ nanosheets derived from metal–organic framework materials (MOFs) under mild conditions, with a urea yield rate of 83.89 μg h⁻¹ mg⁻¹_cat. and faradaic efficiency (FE) of 11.92%. Experimental and theoretical computational analyses confirmed that the defective structures present in the prepared catalysts are conducive to the stabilization and activation of the adsorbed CO₂ and N₂, and the effective promotion of hydrolysis dissociation by Pd provides abundant protons for further hydrogenation after C–N coupling. This work provides some insights into the promotion of hydrolysis dissociation to optimize the hydrogenation energy barriers after C–N coupling for the electrocatalytic synthesis of urea.