Ultrathin 1T-MoS<sub>2</sub> Nanoplates Induced by Quaternary Ammonium-Type Ionic Liquids on Polypyrrole/Graphene Oxide Nanosheets and Its Irreversible Crystal Phase Transition During Electrocatalytic Nitrogen Reduction
Hui Mao, Yuanlin Fu, Haoran Yang, Zizhao Deng, Ying Sun, Daliang Liu, Qiong Wu, Tianyi Ma, Xi‐Ming Song
Abstract
Ultrathin nanoplates of metastable 1T-MoS2 have been successfully stabilized and uniformly distributed on the surface of n-butyl triethyl ammonium bromide functionalized polypyrrole/graphene oxide (BTAB/PPy/GO) by a very simple hydrothermal method. BTAB as a typical kind of quaternary ammonium-type ionic liquids (ILs) played a crucial role in the formation of the obtained 1T-MoS2/BTAB/PPy/GO. It was covalently linked with PPy/GO and arranged in a highly ordered order at the solid–liquid interface of PPy/GO and H2O due to Coulombic interactions and other intermolecular interactions, which would induce and stabilize ultrathin 1T-MoS2 nanoplates by morphosynthesis. The good electrocatalytic activity toward nitrogen reduction reaction (NRR) with strong durability and good stability can be achieved by 1T-MoS2/BTAB/PPy/GO due to their excellent inorganic/organic hierarchical lamellar micro-/nanostructures. Especially, after the long-term electrocatalysis for NRR at a negative potential, metastable 1T-MoS2 as the catalytic center undergoes two types of irreversible crystal phase transition, which was converted to 1T′-MoS2 and Mo2N, caused by the competitive hydrogen evolution reaction (HER) process and the electrochemical reaction between the electroactive 1T-MoS2 and N2, respectively. The new N–Mo bonding prevents Mo atoms from binding to other N atoms in N2, resulting in the deactivation of the electrocatalysts to NRR after being used for 18 h. Even so, quaternary ammonium-type ILs would induce the crystal structures of transition-metal dichalcogenides (TMDCs), which might provide a new thought for the reasonable design of electrocatalysts based on TMDCs for electrocatalysis.