High-pressure microwave-assisted synthesis of WSx/Ni9S8/NF hetero-catalyst for efficient oxygen evolution reaction.

Designing the specific crystal phase with better intrinsic activity and more active sites is a very promising strategy for earth-abundant electrocatalysts for oxygen evolution reaction (OER). Herein, a facile two-step method including the high-pressure microwave and the hydrothermal sulfurization is adopted to prepare the WS_x/Ni₉S₈ hetero-catalyst on nickel foam (WS_x/Ni₉S₈/NF). Firstly, WO₃ polyhedrons homogeneously cover the surface of NF through the high-pressure microwave hydrothermal process. Secondly, WS_x/Ni₉S₈ nanoparticles on the surface of NF can be synthesized after a hydrothermal sulfurization, which has been confirmed by scanning electron microscopy (SEM) elemental mapping and high-resolution transmission electron microscopy (HRTEM). The amorphous WS_x and Ni₉S₈ phase may provide the dual active sites for OER. The electrochemical measurements show that WS_x/Ni₉S₈/NF has superior OER activity with a low overpotential of 320 mV at the current density of 100 mA·cm⁻², better than those of other samples. The enhanced OER performance may be due to the synergistic catalysis from Ni₉S₈ phase and high valence of W. Owing to the stable structure of Ni₉S₈, the long-term stability of WS_x/Ni₉S₈/NF for at least 10 h can be obtained. This work may provide a new approach for the doped nickel sulfides crystal phase through high-pressure microwave hydrothermal assistance for OER. [ABSTRACT FROM AUTHOR]