Improved hydrogen evolution activity by unique NiS2-MoS2 heterostructures with misfit lattices supported on poly(ionic liquid)s functionalized polypyrrole/graphene oxide nanosheets.

NiS 2 -MoS 2 /PVEIB/PPy/GO constructed by unique NiS 2 -MoS 2 heterostructures with misfit lattices composed of cubic NiS 2 , metallic 1T-MoS 2 and semiconductive 2H-MoS 2 as well as PVEIB/PPy/GO nanosheets exhibited the excellent HER activity with strong durability and good stability due to the synergistic effect of each component. The crystal phase transition of MoS 2 from 1T to 1T' phase in NiS 2 -MoS 2 /PVEIB/PPy/GO can be detected by XPS after long-term HER test. • Unique NiS 2 -MoS 2 heterostructures with misfit lattices were immobilized PVEIB/PPy/GO. • The excellent electrocatalytic activity towards HER was achieved. • PVEIB can induce the formation of metallic 1 T-MoS 2 and further facilitate HER. • NiS 2 can effectively prevent the oxidation of MoS 2 exposed in the air. • The transition from 1 T to 1 T'-MoS 2 was detected by XPS after long-term HER test. Unique NiS 2 -MoS 2 heterostructures with misfit lattices composed of cubic NiS 2 , metallic 1 T-MoS 2 and semiconductive 2H-MoS 2 have been immobilized on poly(1-vinyl-3-ethylimidazolium bromide) functionalized polypyrrole/graphene oxide via an ordinary hydrothermal procedure. The obtained NiS 2 -MoS 2 /PVEIB/PPy/GO nanosheets exhibited the excellent electrocatalytic performance for hydrogen evolution reaction (HER). PVEIB played an essential role in the fabrication of this inorganic/organic hierarchical lamellar micro-/nanostructures, which not only played as a good connector between transition metal dichalcogenides (TMDCs) heterostructures and PPy/GO, inducing the formation of metallic 1 T-MoS 2 , but also effectively stabilized more electrons and further facilitate the Heyrovsky reaction for the generation and release of H 2. Though NiS 2 possessed poor conductivity and induced partial 1 T-MoS 2 transformed to 2H-MoS 2 on PVEIB/PPy/GO, the preeminent HER activity was still gained, because NiS 2 could effectively prevent the oxidation of MoS 2 exposed in the atmosphere. Especially, the crystal phase transition of MoS 2 from 1 T to 1 T' phase in NiS 2 -MoS 2 /PVEIB/PPy/GO could be detected by XPS after long-term HER test. Therefore, poly(ionic liquid)s and another metal ion would induce the crystal structures of TMDCs and optimize their electrocatalytic performance, which might afford a new thought towards the reasonable design of electrocatalysts based on TMDCs for electrochemical water splitting. [ABSTRACT FROM AUTHOR]