Mo2P Monolayer as a Superior Electrocatalyst for Urea Synthesis from Nitrogen and Carbon Dioxide Fixation: A Computational Study

Urea synthesis through the simultaneous electrocatalytic reduction of N-2 and CO2 molecules under ambient conditions holds great promises as a sustainable alternative to its industrial production, in which the development of stable, highly efficient, and highly selective catalysts to boost the chemisorption, activation, and coupling of inert N-2 and CO2 molecules remains rather challenging. Herein, by means of density functional theory computations, we proposed a new class of two-dimensional nanomaterials, namely, transition-metal phosphide monolayers (TM2P, TM = Ti, Fe, Zr, Mo, and W), as the potential electrocatalysts for urea production. Our results showed that these TM2P materials exhibit outstanding stability and excellent metallic properties. Interestingly, the Mo2P monolayer was screened out as the best catalyst for urea synthesis due to its small kinetic energy barrier (0.35 eV) for C-N coupling, low limiting potential (-0.39 V), and significant suppressing effects on the competing side reactions. The outstanding catalytic activity of the Mo2P monolayer can be ascribed to its optimal adsorption strength with the key *NCON species due to its moderate positive charges on the Mo active sites. Our findings not only propose a novel catalyst with high-efficiency and high-selectivity for urea production but also further widen the potential applications of metal phosphides in electrocatalysis.

Automated summary

A new class of two-dimensional nanomaterials, transition-metal phosphide monolayers (TM2P, TM = Ti, Fe, Zr, Mo, and W), were proposed as potential electrocatalysts for urea production. The Mo2P monolayer exhibited the best catalytic activity for urea synthesis due to its small kinetic energy barrier, low limiting potential, and suppressing effects on competing side reactions. The optimal adsorption strength with the key *NCON species on the Mo active sites contributed to the outstanding catalytic activity. These findings not only propose a novel catalyst for urea production but also broaden the potential applications of metal phosphides in electrocatalysis.