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

[Display omitted] •An edge site-rich NiS2/MoS2/CNTs heterojunction catalyst was developed via etching.•The etching regulated the electronic and geometric structure of NiS2/MoS2/CNTs.•NiS2/MoS2/CNTs delivered eximious catalytic activity and stability for HER and OER.•The electrolyzer assembled with NiS2/MoS2/CNTs presented outstanding performance. Boosting the hydrogen and oxygen evolution reaction (HER/OER) on MoS2-based catalysts is a challenging scientific issue due to the activity of MoS2 is significantly rely on the edge site which is limited in regular structure. Herein, a highly dispersed edge site-rich NiS2/MoS2/CNTs heterojunction catalyst is successfully developed via facile etching the nanoflower-like NiS2/MoS2 spheres on carbon nanotubes (CNTs). Through expanding the lattice spacing of 2H-MoS2, generating abundant Mo-S edge sites (i.e. generating a large number of unsaturated S atoms) together with enhancing the dispersity of NiS2/MoS2 nanosheets, the etching posttreatment significantly regulates the electronic and geometric structure of NiS2/MoS2/CNTs. Further combining the extremely intimate electronic interaction between MoS2/NiS2 heterogeneous interfaces, the optimal NiS2/MoS2/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 (NiS2/MoS2/CNTs-p), respectively. Moreover, the electrolyzer assembled with NiS2/MoS2/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.