  Great enthusiasm in single atom catalysts (SACs) for the N2 reduction
reaction (NRR) has been aroused by the discovery of Metal (M)-Nx as a promising
catalytic center. However,the performance of available SACs,including poor
activity and selectivity,is far away from the industrial requirement because of
the inappropriate adsorption behaviors of the catalytic centers. Through the
first principles high throughput screening, we find that the rational
construction of Fe-Fe dual atom centered site distributed on graphite carbon
nitride (Fe2/gCN) compromises the ability to adsorb N2H and NH2, achieving the
best NRR performance among 23 different transition metal (TM) centers. Our
results show that Fe2/gCN can achieve a Faradic efficiency of 100% for NH3
production. Impressively, the limiting potential of Fe2/gCN is estimated as low
as -0.13 V, which is hitherto the lowest value among the reported theoretical
results. Multiple level descriptors (excess electrons on the adsorbed N2 and
integrated crystal orbital Hamilton population) shed light on the origin of NRR
activity from the view of energy, electronic structure, and basic
characteristics. As a ubiquitous issue during electrocatalytic NRR, ammonia
contamination originating from the substrate decomposition can be surmounted.
Our predictions offer a new platform for electrocatalytic synthesis of NH3,
contributing to further elucidate the structure-performance correlations.
