  Converting earth-abundant dinitrogen into value-added chemical ammonia is a
significant yet challenging topic. Electrocatalytic nitrogen reduction reaction
(NRR), compared with conventional Haber-Bosch process, is an energy-saving and
environmentally friendly approach. The major task of electrocatalytic NRR is to
find electrocatalysts which can activate dinitrogen effectively and exhibit
high selectivity and stability. Single atom catalysts can act as a good
solution. In this work, by means of first-principles density functional theory,
molecular dynamics calculations, and a two-step screening process, we confirm
that single Sc and Ti atom supported on tetracyanoquinodimethane monolayers
(Sc,Ti-TCNQ) are excellent candidates for NRR electrocatalysts. N2 adsorption
and activation are effective due to the acceptance-donation mechanism and
outstanding electronic structure of TM-TCNQ, and Gibbs free energy diagram
shows that Sc-TCNQ and Ti-TCNQ exhibit low NRR overpotential of 0.33 and 0.22 V
through enzymatic-consecutive mixed pathway, respectively. In addition,
selectivity over HER and stability of Sc/Ti-TCNQ monolayers are also validated.
This work opens a new avenue for designing novel single atom catalysts for NRR
as well as other catalytic applications.
