Ultrathin 1T-MoS₂ Nanoplates Induced by Quaternary Ammonium-Type Ionic Liquids on Polypyrrole/Graphene Oxide Nanosheets and Its Irreversible Crystal Phase Transition During Electrocatalytic Nitrogen Reduction

Abstract

Ultrathin nanoplates of metastable 1T-MoS 2 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-MoS 2 /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 H 2 O due to Coulombic interactions and other intermolecular interactions, which would induce and stabilize ultrathin 1T-MoS 2 nanoplates by morphosynthesis. The good electrocatalytic activity toward nitrogen reduction reaction (NRR) with strong durability and good stability can be achieved by 1T-MoS 2 /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-MoS 2 as the catalytic center undergoes two types of irreversible crystal phase transition, which was converted to 1T′-MoS 2 and Mo 2 N, caused by the competitive hydrogen evolution reaction (HER) process and the electrochemical reaction between the electroactive 1T-MoS 2 and N 2 , respectively. The new N−Mo bonding prevents Mo atoms from binding to other N atoms in N 2 , 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. KEYWORDS: n-butyl triethyl ammonium bromide (BTAB), polypyrrole/graphene oxide (PPy/GO), 1T-MoS 2 , nitrogen reduction reaction (NRR), irreversible crystal phase transition

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