Dual-Silicon-Doped Graphitic Carbon Nitride Sheet: An Efficient Metal-Free Electrocatalyst for Urea Synthesis

Abstract

Searching for an alternative nonhazardous catalyst for direct urea synthesis that avoids the traditional route of NH₃ synthesis followed by CO₂ addition is a challenging field of research nowadays. Based on first-principles calculations, we herein propose a novel electrocatalyst comprising of totally nonmetal earth abundant elements (dual-Si doped g-C₆N₆ sheet) which is capable of activating N₂ and making it susceptible toward direct insertion of CO into the N-N bond, producing *NCON* which is the precursor for urea production by direct coupling of N₂ and CO₂ followed by multiple proton coupled electron transfer processes. Remarkably, the calculated onset potential for urea production is much less than that of NH₃ synthesis and hydrogen evolution reactions, and also the faradaic efficiency is nearly 100% for production urea over ammonia, which promotes exclusive electrocatalytic urea synthesis by suppressing the NH₃ synthesis as well as hydrogen evolution reactions.