Shearing Sulfur Edges of VS2 Electrocatalyst Enhances its Nitrogen Reduction Performance.

Electrochemical N2 fixation requires effective electrocatalysts to expedite the nitrogen reduction reaction (NRR) kinetics and suppress the concomitant hydrogen evolution reaction (HER). Although transition metal sulfides have been deemed as efficient NRR electrocatalysts, it remains a great challenge to suppress the serious HER to achieve high Faradaic efficiency (FE). Herein, vanadium disulfide (VS2 ) is deliberately designed by partially shearing its sulfur (S) edges through a simple calcination treatment at 350 °C. The as-prepared VS2 -350 electrocatalyst exhibits a highest NH3 yield of 20.29 µg h-1 mgcat -1 with a promising FE of 3.86%, which is significantly higher than the counterpart of untreated VS2 (VNH3 : 15.92 µg h-1 mgcat -1 , FE: 1.69%). Experimental and computational results reveal that shearing the S edges can substantially inhibit the HER and expose more V atoms as active sites. Meanwhile, the mechanistic analysis shows that the N2 activation at V active sites follows an "acceptance-donation" mechanism, while the N2 conversion to NH3 follows a hybrid 2 pathway at the VS2 -350 electrocatalyst. This work provides a simple strategy of designing high-performance NRR electrocatalysts based on a deep understanding of the atomic sites dependent catalytical activity.