Structure-activity relationship toward electrocatalytic nitrogen reduction of MoS2 growing on polypyrrole/graphene oxide affected by pyridinium-type ionic liquids.

[Display omitted] • MoS 2 with different crystal phases has been induced by pyridinium-ILs on PPy/GO. • Different electrocatalytic activities towards NRR were achieved due to crystal phase. • Substituent groups in pyridinium were crucial for inducing MoS 2 crystal phase. • The defect-rich 1T/2H-MoS 2 exhibited the best NRR electroactivity and stability. • The conversion of defect-rich 1T/2H-MoS 2 to 1T'-MoS 2 and Mo 2 N occurred after NRR. MoS 2 with different crystal structures and phase compositions have in-situ grown on the surface of pyridinium-type ionic liquids functionalized polypyrrole/graphene oxide (pyridinium-ILs/PPy/GO) and exhibited different electocatalytic performance towards Nitrogen reduction reaction (NRR), affected by the difference of crystal structure and phase compositions of MoS 2 resulting from the induction of substituent groups in pyridinium. Combining the results of NRR performance tests with material characterizations determined by XRD, XPS and Raman spectra to explore the structure-activity relationship toward NRR of MoS 2 /pyridinium-ILs/PPy/GO, pyridinium-ILs with a group containing amino in the para- or ortho -position can be beneficial to induce 1T-MoS 2 with good crystallinity, resulting in the satisfying NH 3 yield, but poor stability, while the hydroxyl group at the para -position in pyridinium-ILs only induce 2H-MoS 2 indexed to JCPDS file number 75-1539, not conducive to nitrogen fixation. Surprisingly, the most excellent NRR electroactivity is achieved by MoS 2 /pyridinium-ILs/PPy/GO synthesized using 2-amino-3-hydroxypyridine with the excellent lamellar hierarchical inorganic/organic micro-/nanostructures. It may be attributed to the confinement effect caused by the stereo hindrance composed of amino group at the ortho -position and hydroxyl group at the meta -position in pyridinium-ILs, resulting in 1T/2H-MoS 2 nanoplates with rich defects indexed to JCPDS file number 37-1492 growing on pyridinium-ILs/PPy/GO. Therefore, the kind and position of substituent groups in pyridinium played an essential role for the crystal structure and phase compositions of MoS 2 growing on pyridinium-ILs/PPy/GO, and further affected the NRR performance, which would provide a new thought and method for the reasonable design and performance optimization of electrocatalysts based on transition metal dichalcogenides for electrocatalysis. [ABSTRACT FROM AUTHOR]