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 NH 3 synthesis followed by CO 2 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-C 6 N 6 sheet) which is capable of activating N 2 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 N 2 and CO 2 followed by multiple proton coupled electron transfer processes. Remarkably, the calculated onset potential for urea production is much less than that of NH 3 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 NH 3 synthesis as well as hydrogen evolution reactions.

Density Functional Theory Studies of Earth-Abundant Late Transition Metal-Substituted Surface + Subsurface Iron Alloys for Selective Electrocatalytic N2 Reduction

“…35,36 The calculated values of low exchange current density (Table S4) and maximum FE (100%) can also support its excellent catalytic activity with faster ammonia production instead of HER (Text S3 and Table S7). 53,54 Co[(hcp(0001)] and Ni[fcc(111)] surface systems have been found to show positive effects on HER activity, as reported previously. 8 However, the observed NRR activity as well as selectivity (Table S5) is found to be improved while considering alloys of Fe with substitution of transition metals (Co/Ni).…”

Identifying and tailoring C–N coupling site for efficient urea synthesis over diatomic Fe–Ni catalyst

“…30 reveal the obvious electronic interaction near the Fermi level over FeNi-N 6 configuration. The bonded diatomic structure derived electron localization around the active site conduces to the urea generation [42][43][44] . It can be seen intuitively that there is a significant charge transfer in FeNi-N 6 as illustrated in the differential charge density maps.…”

Recent Progress in Electrocatalytic Urea Synthesis under Ambient Conditions

“…In other words, the urea synthesis was favorable on these three 2D MBenes. Sarkar et al explored conductive dual-Si doped g-C 6 N 6 sheet as a potential electrocatalyst for urea synthesis through the *NCON hydrogenation (Figure b) . The electroreduction reaction started from N 2 chemisorption on the doped Si atoms with a side-on fashion with −0.42 eV of adsorption energy.…”

“…Sarkar et al explored conductive dual-Si doped g-C 6 N 6 sheet as a potential electrocatalyst for urea synthesis through the *NCON hydrogenation (Figure 10b). 65 The electroreduction reaction started from N 2 chemisorption on the doped Si atoms with a side-on fashion with −0.42 eV of adsorption energy. The subsequent *NCON intermediate was produced from the optimum *N 2 -COOH intermediate reaction path due to its lower applied limiting potential (−0.79 V).…”