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

Abstract

Conversion of CO2 and N2 to urea by electrocatalytic methods under ambient conditions is a promising alternative to conventional urea synthesis method. However, the inherent adsorption and activation characteristics of inert reaction gas molecules and the kinetics of hydrogenation after C-N coupling result in the challenge of electrocatalytic synthesis of urea. In this work, the electrocatalytic conversion of CO2 and N2 to urea by Pd-assisted hydrogenation on CeO2 nanosheets derived from metal-organic framework materials (MOFs) under mild conditions was achieved urea yield rate with 83.89 µg h-1 mg-1cat. and Faradic efficiency (FE) of 11.92%. Combined experimental and theoretical computational analyses confirmed that the defective structures present in the prepared catalysts were conducive to the stabilization and activation of adsorbed CO2 and N2, and due to the effective promotion of hydrolysis dissociation by Pd, which provided abundant source of 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 electrocatalytic synthesis of urea.