Engineering edge sites based on NiS2/MoS2/CNTs heterojunction catalyst for overall water splitting.

[Display omitted] • An edge site-rich NiS 2 /MoS 2 /CNTs heterojunction catalyst was developed via etching. • The etching regulated the electronic and geometric structure of NiS 2 /MoS 2 /CNTs. • NiS 2 /MoS 2 /CNTs delivered eximious catalytic activity and stability for HER and OER. • The electrolyzer assembled with NiS 2 /MoS 2 /CNTs presented outstanding performance. Boosting the hydrogen and oxygen evolution reaction (HER/OER) on MoS 2 -based catalysts is a challenging scientific issue due to the activity of MoS 2 is significantly rely on the edge site which is limited in regular structure. Herein, a highly dispersed edge site-rich NiS 2 /MoS 2 /CNTs heterojunction catalyst is successfully developed via facile etching the nanoflower-like NiS 2 /MoS 2 spheres on carbon nanotubes (CNTs). Through expanding the lattice spacing of 2H-MoS 2 , generating abundant Mo-S edge sites (i.e. generating a large number of unsaturated S atoms) together with enhancing the dispersity of NiS 2 /MoS 2 nanosheets, the etching posttreatment significantly regulates the electronic and geometric structure of NiS 2 /MoS 2 /CNTs. Further combining the extremely intimate electronic interaction between MoS 2 /NiS 2 heterogeneous interfaces, the optimal NiS 2 /MoS 2 /CNTs presents a preeminent alkali water splitting performance with overpotentials of 149 for HER and 315 mV for OER at 10 mA cm−2, which are 29 and 35 mV lower than the catalyst before etch treatment (NiS 2 /MoS 2 /CNTs-p), respectively. Moreover, the electrolyzer assembled with NiS 2 /MoS 2 /CNTs drives a voltage of 1.73 V at 10 mA cm−2 and a continuous stable operation of 50 h toward overall water splitting. [ABSTRACT FROM AUTHOR]