Plasma-assisted synthesis of 2D MoS2 nanosheets with tunable sulfur defects for highly efficient nitrogen reduction reaction

Abstract

Two-dimensional (2D) MoS2 was synthesized in situ with cold plasma at a moderate temperature. The mechanism of exfoliation process by plasma is gas expansion and electron repulsion. Notably, S defects in MoS2 was easily controlled by the treatment time of plasma. The 2D structure exposed a higher number of active sites, and sulfur defects facilitated the activation of nitrogen, thereby enhancing the performance of NRR catalysis. Electrochemical testing demonstrated that the sample achieved a high Faradaic efficiency of 29.04% at −0.2 V relative to a reversible hydrogen electrode (RHE), along with an NH3 yield rate of 10.29 μg h−1 mg−1 cat. at −0.3 V (vs. RHE) in 0.1 M Na2SO4 under ambient conditions. Density functional theory calculations indicated that the catalyzed NRR reaction followed the enzymatic reaction pathway and that the introduction of S defects effectively reduced the reaction energy barrier and promoted the protonation of N2 molecules.