LAUSR

Defects in transition metal dichalcogenides (TMDs) can serve as active sites in catalytic reactions. In this work, by means of first-principles calculations, the catalytic activities of WX 2 (X = S, Se, Te) monolayers in the 1T' phase with both vacancy defects (missing chalcogen atoms, X V d ) and antisite defects (replacing chalcogen atoms with W atoms, X A d ) are evaluated for the nitrogen reduction reaction (NRR). Our results show that all these defective catalysts have great potential toward electrocatalytic ammonia synthesis by exhibiting fairly low limiting potentials (U L ). Especially, over 1T'-WTe 2 @ Te V d , 1T'-WS 2 @ S A d , 1T'-WSe 2 @ Se A d and 1T'-WTe 2 @ Te A d , the corresponding U L values are -0.49, -0.21, -0.19 and -0.15 V, much smaller than that of the benchmark catalyst, the Ru (0001) surface (U L = -0.98 V). Furthermore, the hydrogen evolution reaction (HER) is inhibited. 1T'-WX 2 monolayers with the antisite defects show better NRR activity than those with the vacancy defects, because of the smaller steric hindrance at the former. Our results suggest that the steric effect at the active surface sites should be utilized to develop better catalysts.