Electrocatalytic synergy from Ni-enhanced WS2 for alkaline overall water splitting with tuning electronic structure and crystal phase transformation

Due to the limited active sites and poor conductivity, the application of tungsten disulfide (WS 2 ) in alkaline water electrolysis remains a challenge. Herein, Ni-WS 2 nanosheet arrays were in situ grown on the carbon fiber paper (Ni-WS 2 /CFP) as an electrocatalyst for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline media, and the introduction degree of Ni can be regulated by adjusting the electrodeposition time. When the electrodeposition time is 3 min, Ni ions are doped into the lattice of WS 2 , and by prolonging the electrodeposition time to 10 min, the nickel disulfide (NiS 2 ) crystal phase is generated to form NiS 2 @WS 2 heterojunction. The optimized Ni-WS 2 /CFP-10 min catalyst requires the overpotentials of 65 mV for HER and 251 mV for OER to achieve the current density of 10 mA cm −2 . A two-electrode water electrolysis device employing the Ni-WS 2 /CFP-10 min electrocatalyst requires a cell voltage of 1.63 V at the current density of 10 mA cm −2 . This work provides a new perspective for enhancing the electrocatalytic performance of WS 2 -based electrocatalysts by introducing heteroatoms and constructing heterojunction.