Unveiling the Underlying Mechanism of Transition Metal Atoms Anchored Square Tetracyanoquinodimethane Monolayers as Electrocatalysts for N2 Fixation

We for the first time systematically studied the structures and electrochemical nitrogen reduction reaction properties of two-dimensional single transition-metal anchored square tetracyanoquinodimethane monolayers (labeled as: TM-sTCNQ, TM = 3d, 4d, 5d series transition metals) by employing density functional theory method. Through high-throughput screenings and full reaction path researches, two promising electrochemical nitrogen reduction reaction catalysts Nb-sTCNQ and Mo-sTCNQ have been obtained. The nitrogen reduction reaction onset potential on Nb-sTCNQ is as low as -0.48 V. Furthermore, the Nb-sTCNQ catalyst can quickly desorb NH3 produced with a free energy of 0.65 eV, giving Nb-sTCNQ excellent catalytic cycle performance. The high catalytic activity of the two materials might be attributed to the effective charge transfer between the active center and adsorbed N-2, which enables the active center to adsorb and activate inert N-2 molecules well, and the reduction processes require small energy input (i.e., the maximum free energy changes are small). This work provides insights for finding highly efficient, stable, and low-cost nitrogen reduction reaction electrocatalysts. We hope our results can promote further experimental and theoretical research of this field.

Automated summary

In this study, the structures and electrochemical properties of two-dimensional single transition-metal anchored square tetracyanoquinodimethane monolayers were systematically studied using density functional theory. Two promising electrochemical nitrogen reduction reaction catalysts, Nb-sTCNQ and Mo-sTCNQ, were obtained through screenings and reaction path research. The high catalytic activity of these catalysts can be attributed to the effective charge transfer and small energy input required for the reduction processes.