Establishing theoretical landscapes of identifying electrocatalysts for urea synthesis via dispersed dual-metals anchored on Ti2CO2 MXene

Urea synthesis via electrochemical C-N coupling reaction holds great promise as a sustainable alternative to its industrial production, in which the efficient electrocatalysts that can facilitate the activation of inert N-2 molecules and the following C-N coupling are still in lack. Herein, we employ density-functional theory (DFT) to establish a theoretical landscape of dispersed dual-metals anchored on Ti2CO2 MXene (M-2@Ti2CO2 and MM'@Ti2CO2) as electrocatalysts for urea synthesis. By calculating the Gibbs free energy diagrams of urea electrosynthesis, we find that there are three typical uphill steps, including the C-N coupling step and the last two hydrogenation reactions. To efficiently screen electrocatalysts, we propose a criterion that Gibbs free energy differences are all less than 0.50 eV (Delta G < 0.5 eV) for these three uphill steps. As a result, five promising electrocatalysts for urea synthesis are screened out from 28 stable systems, in which VMn@Ti2CO2 exhibits ultralow limiting potential ( 0.26 V) as well as significant inhibition of competitive reactions. Moreover, Delta G values of the three uphill steps have been linearly fitted to obtain their corresponding principle descriptors. Meanwhile, the effective ranges of these descriptors are also established, including bond length of chemisorbed *N-2 (1.16 angstrom < lN N < 1.23 angstrom), adsorption energies of *NHCONH and *NH2CONH2 (-6.1 eV < E-ad (*NHCONH) < -5.3 eV and -0.3 eV < E-ad (*NH2CONH2) < 0.2 eV), respectively. This study not only indicates that dispersed dual-metals anchored on Ti2CO2 MXene can serve as efficient active sites for urea electrosynthesis but also defines descriptors and their effective ranges for high-throughput screening of electrocatalysts.